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Service TrainingMeeting Guide 681 SERV1681-01

January 2002

TECHNICAL PRESENTATION

3500 ENGINE CONTROLS

ELECTRONIC UNIT INJECTION

TOPRELUBRICATION

PUMP

+ BATTERY

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR

J3/P3 MACHINEINTERFACE

CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR

J4/P4 THROUGHJ19/P19

J2

J1

ECM

UNFILTERED OILPRESSURE

SENSOR

AFTERCOOLERTEMPERATURE

SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29

RIGHTTURBOCHARGERINLET PRESSURE

SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR

FUEL FILTERDIFFERENTIAL

PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH

FILTERED OILPRESSURE

SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

LEFTTURBOCHARGERINLET PRESSURE

SENSOR

J28/P28

J35/P35

THROTTLEPOSITIONSENSOR

THROTTLEBACK-UPSWITCH

WASTEGATECONTROL SOLENOID

USER DEFINED SHUTDOWN

GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY

ENGINE FANCONTROLSOLENOID

A/C ONSWITCH

FAN SPEED SENSOR

+ BATTERY

RELAYCYLINDER

ENGINE

ETHER START VALVE

STARTINGAID SWITCH

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

J27/P27

J48/P48

P84/J84

P41/J41

308-YL

113-OR

BASIC ENGINE BLOCK DIAGRAM APPLICATION BLOCK DIAGRAM

ELECTRONIC SERVICETOOL CONNECTOR

TO VIMS, EPTC II ORMONITORING SYSTEM

DISCONNECTSWITCH

OIL RENEWALCONTROL SOLENOID

15 AMPBREAKER

COOLANTTEMPERATURE

SENSOR


RELAY

J21/P21

J47/P47

J103/P103

J113/P113

P31/J31

3500B ENGINE CONTROLSELECTRONIC UNIT INJECTION (EUI)

MEETING GUIDE 681 SLIDES AND SCRIPT

AUDIENCE

Level II - Service personnel who understand the principles of engine systems operation, diagnosticequipment, and procedures for testing and adjusting.

CONTENT

This presentation is designed to prepare a service technician to identify the components, explain theirfunction, and service the 3500B Electronic Unit Injection (EUI) engines in current machineapplications.

OBJECTIVES

After learning the information in this presentation, the serviceman will be able to:

1. Locate and identify the major electrical/electronic components in the 3500 EUI system.

2. Explain the functions of the major electrical/electronic components in the 3500 EUI system.

3. Trace the flow of fuel and oil through the fuel system.

4. Trace the flow of current through the engine electrical system.

PREREQUISITES

Interactive Video Course "Fundamentals of Electrical Systems" (CD ROM) TEMV9002Service Technician Workbench Tutorial (CD ROM included with STW software) NEHS0812Caterpillar Machine Electronics Course (Five Modules) SEGV3001 - SEGV3005Caterpillar 3500B MEUI Fuel System (CD ROM) RENR1395

Prior training in mechanical systems operation and testing and adjusting procedures for 3500B enginesshould be completed before participating in this training session. The participants should have PC skillsand have completed training in the current Windows® operating system. Additionally, participantsshould have completed training in the most current Electronic Technician (ET) software.

Estimated Time: 8 HoursVisuals: 101 (2 X 2) SlidesServiceman Handouts: 6 Drawings/Data SheetsForm: SERV1681-01Date: 1/2002

© 2002 Caterpillar Inc.

REFERENCES

Troubleshooting Guide "3500B Engines--Caterpillar Machines" SENR1128Specifications "3500B Engines--Caterpillar Machines" SENR1122Systems Operation, Testing and Adjusting "3500B Engines--Caterpillar Machines" SENR1123

SUPPLEMENTARY TRAINING MATERIAL

Brochure "Service Technician Workbench" NELG0028Brochure "Caterpillar Electronic Technician" NEDG6015

Service Technician Workbench Tutorial (Included with STW software) NEHS08123500 and 3500B Series of Diesel Engines LERV1450Introduction to the 3500B Series Engine LEPV5149

EUI SERVICE TOOLS

Software and ManualsCaterpillar Service Tool Software/Getting Started Guide - Service Technician Workbench NEHS0796or Caterpillar Service Tool Software/Getting Started - Caterpillar Electronic Technician JEBD3003Caterpillar Service Tool Software/Users Manual- Communication Adapter II NEHS0758

Mechanical ToolsEngine Turning Tool 9S-9082Injector Height Setting Tool Group 9U-5132Base for 9U-5132 (specific to 3500B) 125-2744

Electronic ToolsLaptop computerCommunication Adapter II (Group) 171-4400Cable, PC to Communication Adapter 96-0055Cable, Communication Adapter to Machine 160-0133Caterpillar Digital Multimeter 146-4080Three Pin DT Breakout Harness 7X-6370Cable Probes 7X-1710Auxiliary ECM Power Supply Harness 167-9225Timing Calibration Probe (Magnetic Pickup) 6V-2197Timing Calibration Probe Adapter Sleeve 7X-1171Timing Calibration Probe Cable 7X-1695

STMG 681 - 3 -1/02

TABLE OF CONTENTS

INTRODUCTION ..................................................................................................................5Overview...........................................................................................................................6EUI Fuel System Components..........................................................................................8External Engine Views and Major Components .............................................................11Electronic Timing Components ......................................................................................18Machine Mounted Engine Components..........................................................................32Other Systems Controlled by the ECM ..........................................................................34

ELECTRONIC CONTROL SYSTEM.................................................................................36Fuel Injection ..................................................................................................................39Fuel Injection Control System ........................................................................................41

FUEL SUPPLY SYSTEM ....................................................................................................57Fuel Supply Circuit .........................................................................................................58Fuel Supply Components................................................................................................60

SYSTEM POWER SUPPLIES.............................................................................................64ECM Power Supply ........................................................................................................65Speed/Timing Sensor Power Supply...............................................................................68Injector Power Supplies ..................................................................................................69Analog Sensor Power Supply .........................................................................................70Digital Sensor Power Supply ..........................................................................................71Wastegate Control Solenoid Power Supply ....................................................................72

ELECTRONIC SENSORS AND SYSTEMS ......................................................................74Speed/Timing Sensing Circuit ........................................................................................76Analog Sensors and Circuits...........................................................................................78Engine Mounted Switches ..............................................................................................90Digital Sensors and Circuits............................................................................................92Engine Shutdown Systems..............................................................................................98Ether Injection System..................................................................................................100Demand Fan Controls ...................................................................................................101CAT Data Link..............................................................................................................102Pre-lubrication System..................................................................................................104Logged Events ..............................................................................................................105

APPLICATION SPECIFIC SYSTEMS..............................................................................107Oil Renewal System......................................................................................................108Wastegate Control .........................................................................................................110

SLIDE LIST........................................................................................................................112

SERVICEMAN'S HANDOUTS .........................................................................................114

STMG 681 - 4 -1/02

• Major topics

1

INTRODUCTION

This presentation discusses the 3500B Electronic Unit Injection (EUI)Engine Controls used in machine applications.

The topics are sequenced as follows:

- Introduction and Major Components

- Electronic Control System

- Fuel Supply System

- System Power Supplies

- Electronic Sensors and Systems

- Application Specific Systems

INSTRUCTOR NOTE: This presentation requires competence inElectronic Technician (ET) programming and operations for 3500Bengines.

STMG 681 - 5 -1/02

3500B ENGINE CONTROLS

ELECTRONIC UNIT INJECTION (EUI)

2002 Caterpillar Inc.

• 3500 EUI applications

• System features

2

Overview

The 3500B engines were direct replacements for the original 3500 Seriesengines. Many additional features and benefits have been incorporatedinto the 3500B Series which will be described later in the presentation.

The 3500B engines equipped with Electronic Unit Injection (EUI) areavailable in construction equipment and industrial applications.

Caterpillar machines currently powered by 3500 EUI engines include:

Off-highway Trucks 777 - 793

Wheel Loaders 992 - 994

Track-type Tractors D11

Excavators 5130 - 5230

This list is generic and includes both the original 3500 Series engines andthe 3500B engines.

The 3500 EUI engines have many features and benefits not possible withmechanical fuel systems. These features include a very clean exhaust,improved fuel consumption and cold starting, simplified maintenancewith fewer moving parts, and reduced operating costs.

STMG 681 - 6 -1/02

• Engine crosssectional view

3

This cross sectional view of the engine shows the injector installation andthe pushrod arrangement in relation to the upper portion of the engine.

This sectional view is similar to the original 3500 EUI engine. Majordifferences are the spring loaded injector push rods and the largerdiameter camshaft (described later).

STMG 681 - 7 -1/02

STMG 681 - 8 -1/02

4

• Electronically similarto HEUI system

• Injectors electronicallysignalled

FUEL TANK

PRIMARYFUEL

FILTER

SECONDARYFUEL FILTERS

(2 MICRON)

ENGINEBLOCK

OIL RENEWALINJECTOR

FUELPRESSURE

REGULATOR

FUELTRANSFER

PUMPFUELHEATER

ECM

3516B FUEL SUPPLY CIRCUIT (793C)

PRIMING PUMP SUPPLY

FUELDIFFERENTIAL

PRESSURESWITCH

CYLINDERHEAD

EUI Fuel System Components

This schematic shows the various components in the 3500B EUI fueldelivery system. A detailed explanation of the system and the variouscomponents follows later in this presentation. The schematic aboveshows the 3516B fuel system as installed in the 793C Off-highway Truck.

The electronic components in the 3500B EUI fuel system are very similarto those used in other EUI and, to some extent, the HEUI electronicsystem. However, in this system, the injectors are actuated by camshafts.The injectors are electronically signalled, as in the original 3500 EUIsystem.

STMG 681 - 9 -1/02

5

• Electrical blockdiagram

TOPRELUBRICATION

PUMP

+ BATTERY

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35





GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY


A/C ONSWITCH

FAN SPEED SENSOR

+ BATTERY

RELAYCYLINDER

ENGINE

ETHER START VALVE

STARTINGAID SWITCH

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

J27/P27

J48/P48

P84/J84

P41/J41

308-YL

113-OR




DISCONNECTSWITCH


15 AMPBREAKER

COOLANTTEMPERATURE

SENSOR


RELAY

J21/P21

J47/P47

J103/P103

J113/P113

P31/J31

This electrical schematic shows the various components in the system andthe section of the system in which they are located.

On the left side of the schematic are the engine mounted components, andon the right side of the schematic are the machine mounted components.The connection between the two circuits is made by the Machine InterfaceConnector.

Some components or circuits are not used by the fuel system, but arecontrolled by the engine ECM. For example:

- Pre-lubrication Circuit

- Exhaust Wastegate Control

- Demand Fan Control

- Ether Injection System

• Six major componenttypes:

- ECM

- Throttle control

- Pressure sensor

- Temperature sensor

- Speed/timing sensor

- Injector

6

This slide shows six major types of electrical/electronic components inthe EUI fuel system:

- ECM

- Throttle Control

- Pressure Sensor

- Temperature Sensor

- Speed/Timing Sensor

- Injector

The CAT Data Link (not shown) provides a two-way communication pathbetween the EUI system and the other ECM’s or systems on the machine.The CAT Data Link also allows the ET service tool to communicate withthe engine ECM.

NOTE: Only one example of each sensor (pressure and temperature) isshown on the slide.

STMG 681 - 10 -1/02

• Engine front view

• ECM (arrow)

• Additionalcomponents:

- Timing calibrationconnector

- Coolant flow sensor

- Turbocharger outletpressure sensor

7

External Engine Views and Major Components

The engine block is similar to the original 3500 block. The maindifference is due to the larger camshaft which needs a larger bore in theblock to accommodate the camshaft.

The principal component in the EUI system is the Electronic ControlModule (ECM). The ECM (arrow) is mounted at the front of the engine.

The following components are also located on the front of the engine:

- Timing Calibration Connector

- Coolant Flow Sensor

- Turbocharger Outlet Pressure Sensor

STMG 681 - 11 -1/02

• Engine rear view

1. Aftercoolertemperature sensor

2. Machine interfaceconnector

3. Speed/timingsensor

8

At the rear of the engine is the timing gear housing containing thefollowing components:

- Aftercooler Temperature Sensor (1)

- Machine Interface Connector (2)

- Speed/Timing Sensor (3)

STMG 681 - 12 -1/02

1

3

2

• Engine left side view

1. Coolanttemperature sensor


3. Fuel filters

4. Oil filters

9

On the left side of the engine are the following components:

- Coolant Temperature Sensor (1) on the thermostat housing

- Speed/Timing Sensor (2)

- Fuel filters (3)

- Oil Filters (4)

Additional components mounted on this side of the engine (to beexplained later in the presentation) are:

- Exhaust Temperature Sensor (one of two)

- Filtered Oil Pressure Sender

- Unfiltered Oil Pressure Sender

STMG 681 - 13 -1/02

2

1

4

3

• Engine right side view

1. Crankcasepressure sensor

2. Oil renewal injector

3. Fuel transfer pump

4. Coolant flow switch

5. Timing calibrationconnector

10

On the right side of the engine are the following components:

- Crankcase Pressure Sensor (1)

- Oil Renewal Injector (2)

- Fuel Transfer Pump (3)

- Coolant Flow Switch (4)

- Timing Calibration Connector (5)

Additional components on this side of the engine include:

- Right Exhaust Temperature Sensor

- Oil Level Switch

- Wiring Harness

The wiring harness includes the Deutsch electrical connectors on thecylinder heads. The Deutsch connectors conduct current to the electronicunit injectors through internal wiring in the cylinder heads.

STMG 681 - 14 -1/02

2

3

54

1

• ECM--the "heart" ofthe system

• Personality moduleaccess panel locatedon rear of ECM

11

The major component in the EUI system is the Electronic ControlModule.

The ECM is the "heart" of the engine. The ECM performs enginegoverning, timing and fuel limiting. It also reads sensors andcommunicates to the instrument display system through the CAT DataLink.

The Personality Module is located on the rear of the ECM through anaccess panel.

The Personality Module is used to program the ECM with all the ratinginformation for a particular application. The Personality Module can bechanged by direct replacement or can be flash programmed (orreprogrammed) using a PC.

STMG 681 - 15 -1/02

• EUI wiring harness

12

The wiring harness provides two-way communication between the ECMand the engine sensors and connects the ECM to the unit injectors.

The harness is routed from the ECM at the left front of the engine to theleft side of the engine. The harness then crosses over to the right rear ofthe engine and is routed to the right side of the engine.

STMG 681 - 16 -1/02

• Coolant temperaturesensor (arrow)

• Sensor functions

13

The engine Coolant Temperature Sensor (arrow) is located at the frontof the engine on the thermostat housing. This sensor is used with theECM to control various functions. The following systems or circuits usethe Temperature Sensor output to the ECM:

The Vital Information Management System (VIMS) or CaterpillarMonitoring System Coolant Temperature Gauge over the CAT DataLink.

The High Coolant Temperature Warning Alert Indicator and Gaugeon the VIMS or Caterpillar Monitoring System panel. (Theinformation is transmitted over the CAT Data Link.)

The Engine Demand Fan Control, if installed, uses the sensor signalreference to provide the appropriate fan speed.

The Cat Electronic Technician (ET) status screen for coolanttemperature indication.

The Cold Mode engine control (i.e. elevated low idle and timingreference for cold mode operation).

The Ether Aid control as a reference for Ether Aid operation.

STMG 681 - 17 -1/02

• Speed/timing sensor(arrow)

• Self-adjusting sensor

14

Electronic Timing Components

This view shows the Speed/Timing Sensor (arrow). The sensor ismounted on the rear gear housing.

This sensor is used to calculate engine speed and crankshaft position fortiming purposes.

The sensor is self-adjusting, but special precautions are necessary duringinstallation to prevent damage. (The precautions are described later in thepresentation.)

NOTE: After installation, the sensor is initially in contact with thetiming wheel.

STMG 681 - 18 -1/02

• Identify components:

1. Timing wheel


3. Dowel pin

4. 50/50 size slot andtooth

15

This view shows the Timing Wheel (1) and the Speed/Timing Sensor(2) on the engine.

A dowel pin (3) on the camshaft and a corresponding hole on the timingwheel are used to time the wheel relative to the camshaft. The camshaftis then timed with the crankshaft at TDC.

Notice the wide 50/50 size slot and equal size tooth (4) cut in the wheel.Three pairs of equal size slots and teeth are on the wheel. The other 21slots and teeth are 80/20 relative size. These features are used to generatea digital signal necessary for timing.

These functions are more fully explained later in the second section ofthis presentation.

This timing wheel is common to all 3500 engines.

STMG 681 - 19 -1/02

4

3

2

1

• Timing wheel (arrow)

16

The timing wheel (arrow) is mounted on and driven by the left camshaft(not shown). The camshaft is driven by the rear gear train, as shown inthis slide.

STMG 681 - 20 -1/02

• 3500B camshaft

17

Each cylinder has three corresponding camshaft lobes. The center lobe isis used to actuate the unit injector. The 3500B has a larger diametercamshaft to accommodate the higher injection pressures generated in theunit injector pumps.

The cylinder block has a larger camshaft bore to accommodate the largercamshaft. (All 3500 engines are now being manufactured to thisstandard.)

STMG 681 - 21 -1/02

• injector pushrodspring

18

The injectors are actuated by the camshaft. This view also shows thevalve train which is on both sides of the injector mechanism below thevalve cover.

Notice the 3500B injector pushrod spring, which maintains contactbetween the lifter roller and the camshaft lobe. This spring is designed tomaintain cam follower and camshaft contact and protect the mechanismduring a possible overspeed.

STMG 681 - 22 -1/02

• 3500B EUI injector

• 105 Volt signaldetermines start ofinjection

19

The 3500B EUI injector is actuated by the pushrod and rocker arm. Fuelflow is controlled by the ECM through a solenoid on the side of theinjector.

The injection cycle is initiated and terminated by the ECM with a 105 Volt signal. The start of injection and, therefore, timing aredetermined by the start of the signal. The duration of the signal from theECM (and rpm) determines the quantity of fuel delivered per stroke. Thisoperation is explained in more detail in the Electronic Controls section ofthe presentation.

STMG 681 - 23 -1/02

1. Fuel pressureregulator

2. Fuel lines toinjectors

20

The Fuel Pressure Regulator (1) is located on the top right side of theengine.

Fuel flows from the fuel filter base, through the steel fuel lines (2), to theEUI fuel injectors. Return fuel from the injectors flows through the fuelpressure regulator before returning to the fuel tank. Fuel pressure iscontrolled by the fuel pressure regulator.

STMG 681 - 24 -1/02

1

2

• Atmospheric pressuresensor (arrow)

21

The Atmospheric Pressure Sensor (arrow) is installed on the ECMmounting adapter and is vented to the atmosphere. This sensor hasvarious functions which are fully described later in the presentation.Briefly, it performs the following functions:

Ambient pressure measurement for automatic altitudecompensation and automatic air filter compensation.

Absolute pressure measurement for the fuel ratio control, ET, filterrestriction, and Caterpillar Monitoring System panel (gauge) pressurecalculations.

STMG 681 - 25 -1/02

1. Turbocharger inletpressure sensor

2. Ether cylinders

22

The Turbocharger Inlet Pressure Sensor (1) is mounted between the airfilter and the turbocharger.

This sensor is used in conjunction with the atmospheric pressure sensor tomeasure air filter restriction for engine protection purposes. Thedifference between the two pressure measurements is used as the filterdifferential pressure. The engine ECM uses this calculation to determinewhether derating is necessary to protect the engine against the effects ofexcessive filter restriction.

This function is referred to as Automatic Air Filter Compensation.

Depending on the application and air intake system configuration, eitherone or two Turbocharger Inlet Pressure Sensors may be used.

If the machine is equipped with an ether start system, the ECM willautomatically inject ether from the ether cylinders (2) during cranking.The operator can also inject ether manually with the ether switch in thecab. Ether will only be injected if the engine coolant temperature isbelow 10°C (50°F) and engine speed is below 1200 rpm.

STMG 681 - 26 -1/02

1

2

• Turbocharger outletpressure sensor(arrow)

23

Also at the front of the engine in the vee is the Turbocharger Outlet(Boost) Pressure Sensor (arrow). This sensor is used with the ECM tocontrol the air/fuel ratio electronically. This feature allows more accuratesmoke control which was not possible with previous mechanicallygoverned engines. The sensor reads boost pressure through a tubeconnecting the sensor to the manifold.

The sensor also allows boost pressure to be read using the electronicservice tools.

STMG 681 - 27 -1/02

• Exhaust temperaturesensor (arrow)

24

One Exhaust Temperature Sensor (arrow) is mounted below eachturbocharger. These sensors are used to warn of possible damagingconditions in the engine caused by excessive exhaust temperature.

On the 793C, the sensors enable the ECM to derate the engine.

STMG 681 - 28 -1/02

• Filtered lubrication oilpressure sensor(arrow)

25

Mounted on the rear of the Oil Filter Group is the Filtered LubricationOil Pressure Sensor (arrow). This sensor is used to signal oil pressure tothe ECM. The sensor is also used by the ECM to generate a low oilpressure warning for the operator.

Mounted at the front of the Oil Filter Group (not shown) is the UnfilteredLubrication Oil Pressure Sensor. This sensor is used by the ECM withthe Filtered Lubrication Oil Pressure Sensor to calculate oil filterdifferential pressure.

The oil filter differential pressure calculation provides a warning that theoil filters need to be changed. (This system is not designed to be asubstitute for regular filter change maintenance requirements.)

STMG 681 - 29 -1/02

• Crankcase pressuresensor (arrow)

26

A Crankcase Pressure Sensor (arrow) may be mounted on the right sideof the engine.

This sensor is used to protect the engine by giving advance warning of afailure (i.e. a piston allowing excessive blowby which could soon causeconsiderable damage).

STMG 681 - 30 -1/02

• Timing calibrationsensor (arrow)

27

The Timing Calibration Sensor (arrow) is installed when required forspeed/timing sensor calibration in the flywheel housing.

This sensor (magnetic pickup) is installed in the hole normally reservedfor the timing pin. (The pin is used to position the crankshaft with theNo. 1 piston at top dead center.)

NOTE: On some applications (i.e. track-type tractors) whereaccessibility is limited, this sensor is permanently installed.

STMG 681 - 31 -1/02

• Machine mountedcomponents:

1. Brake pedal

2. Throttle pedal

3. Throttle positionsensor

• Elevated low idle

• Throttle back-upswitch

28

Machine Mounted Engine Components

Machine mounted components on off-highway trucks include:

- Brake pedal (1)

- Throttle pedal (2)

- Throttle Position Sensor (3)

The Throttle Position Sensor is attached to the throttle pedal. TheThrottle Position Sensor provides the throttle position input to the ECM.

The ECM provides an elevated engine idle speed of 1300 rpm when thecoolant temperature is below 60°C (140°F). Above 60°C (140°F), theelevated idle rpm is gradually reduced until the coolant temperaturereaches 71°C (160°F). Above 71°C (160°F), the engine will idle at 700 rpm.

Increasing the low idle speed helps prevent incomplete combustion andovercooling. To temporarily reduce the elevated idle speed, the operatorcan depress the throttle momentarily, and the idle speed will decrease to700 rpm for 10 minutes.

The Off-highway Truck Throttle Back-up Switch allows a "limp home"mode in the event of a throttle circuit failure.

STMG 681 - 32 -1/02

1

2

3

• Fuel filters

• Filter differentialpressure switch

• Two micron fuel filterrating

29

Two fuel filters are installed on the left side of the engine. The primingpump is installed on the filter housing.

A fuel filter differential pressure switch is installed on the front of thefilter housing to provide a warning when the filters need replacement.

It is important that the correct two micron fuel filters are used with thisengine.

STMG 681 - 33 -1/02

30

Other Systems Controlled by the ECM

Although not actually part of the fuel system, the following circuits arealso controlled by the ECM.

- Oil Renewal

- Exhaust Wastegate Control

- Engine Oil Prelube

- Variable Speed Fan Control

- Ether Injection System

These circuits are described later in the presentation.

STMG 681 - 34 -1/02

OTHER SYSTEMS CONTROLLED BY THE ECM

• Oil Renewal

• Exhaust Wastegate Control

• Engine Oil Prelube

• Variable Speed Fan Control

• Ether Injection System

STMG 681 - 35 -1/02

31

• Engine componentidentification

TOPRELUBRICATION

PUMP

+ BATTERY

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35





GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY


A/C ONSWITCH

FAN SPEED SENSOR

+ BATTERY

RELAYCYLINDER

ENGINE

ETHER START VALVE

STARTINGAID SWITCH

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

J27/P27

J48/P48

P84/J84

P41/J41

308-YL

113-OR




DISCONNECTSWITCH


15 AMPBREAKER

COOLANTTEMPERATURE

SENSOR


RELAY

J21/P21

J47/P47

J103/P103

J113/P113

P31/J31

This schematic identifies the external EUI engine components for the793C Truck. The components shown on the left side of the schematic aremounted on the engine and those on the right are machine mounted.

Other machines may differ with the mix of sensors and other components.The appropriate Troubleshooting Guide must be used to verify the specificmachine components.

INSTRUCTOR NOTE: At this time, it is recommended that eachcomponent be located on the engine and machine. The function ofeach can be reviewed with the students.

32

ELECTRONIC CONTROL SYSTEM

This section of the presentation explains the 3500B Electronic ControlSystem including the following components:

- ECM

- Personality Module

- Electronic Unit Injector Solenoids

- Timing Wheel

Also covered are the following subsystems and related procedures:

- Timing control

- Fuel quantity control

- Speed control (governor)

- Cold modes

- Timing calibration

STMG 681 - 36 -1/02

ELECTRONICCONTROL SYSTEM

• ECM:

- Governor

- Fuel systemcomputer

- Injection timingcontroller

• Same ECM used in all3500B applications

• 3500B EUI ECM notinterchangeable with3400E HEUI ECM

33

The Electronic Control Module (ECM) functions as the governor and fuelsystem computer. The ECM receives all the signals from the sensors andenergizes the injector solenoids to control timing and engine speed.

The ECM is sealed except for access to the software which is contained inthe Personality Module (next slide). This ECM is the second generationof Advanced Diesel Engine Management Systems and is often referred toas "ADEM II."

This ECM is used on all 3500B engines, including machine and industrialapplications.

This ECM physically looks the same as the 3400 HEUI ECM. However,it is very different electrically in that the wave form (described later in thepresentation) for the injectors has a different shape. Additionally, thisECM has no pump control valve output.

NOTE: The ECM has an excellent record of reliability. Therefore,any problems in the system are most likely to be in the connectorsand wiring harness. In other words, the ECM should typically be thelast item in troubleshooting.

STMG 681 - 37 -1/02

• Personality modulecontains software

• ECM is sealed exceptfor personality module

34

The Personality Module (shown here removed from the ECM) containsthe software with all the fuel setting information (such as horsepower,torque rise and air/fuel ratio rates) which determines how the engine willperform. The Personality Module is installed on the lower face of theECM, behind the access panel.

At this time, two methods can be used to update the software:

1. Remove and replace the Personality Module.

2. Flash Programming: Electronic reprogramming of the PersonalityModule.

NOTE: The ECM is sealed and needs no routine adjustment ormaintenance. The Personality Module is mounted within the ECM.Installation of the Personality Module is the only reason to enter theECM. This operation would normally be performed during an ECMinstallation or a software update.

STMG 681 - 38 -1/02

• Unit injectors

• Electrically signalled,mechanically actuated

• Injector codes

• Programming injectorcodes

35

Fuel Injection

The 3500B EUI injector is very similar to the original 3500 EUI injector.The injector is controlled electrically by the ECM. The signal from theECM controls the opening and closing of the solenoid valve. Thesolenoid valve controls the flow of high pressure fuel to the cylinder.This system enables the ECM to control fuel volume and timing.

The 3500B injector now has bar and numerical codes marked on thetappet. The numerical code must be entered into the ECM using ET. Thepurpose of this code is to ensure that all injectors are matched as perfectlyas possible in performance, both in timing and fuel quantity.

If an injector is replaced, moved to another position on the engine, or iftwo injectors are switched, then the injector codes must be reprogrammed.

The injector codes are programmed into the ECM using ET and theCalibrate Sensor Screen. Failure to enter the codes into a new ECM mayresult in unequal timing and fuel delivery between cylinders.

The injector solenoids operate on 105 Volts direct current. Alwaysremain clear of the injector area when the engine is running orelectrical shock may occur.

STMG 681 - 39 -1/02

WARNING

• Injector testing

36

These tests can be used to determine which cylinder or injector ismalfunctioning:

INJECTOR SOLENOID TESTThis test is performed while the engine is stopped. The injector solenoidscan be tested automatically with ET using the Injector Solenoid Test.This function individually tests each solenoid in sequence and indicates ifa short or an open circuit is present.

CYLINDER CUT-OUT (Manual test)This test is performed while the engine is running at any speed. The 105 Volt pulses can be individually cut out to aid in troubleshootingmisfire problems in the injector and the cylinder.

AUTOMATIC CYLINDER CUT-OUTThis test is performed with ET while the engine is running at any speed.The test makes a comparative evaluation of all injectors and numericallyshows the results. The test enables an on-engine evaluation of theinjectors. A satisfactory test of all injector solenoids without anydiagnostic messages means that a problem is likely mechanical and in thecylinder.

(AUTOMATIC) MULTIPLE CYLINDER CUT-OUTThis test is performed with current engines and enables multiple cylindersto be cut-out simultaneously.

STMG 681 - 40 -1/02

• INJECTOR SOLENOID TEST

• CYLINDER CUT-OUT

• AUTOMATIC INJECTOR TEST

EUI INJECTOR TESTINGMETHODS

STMG 681 - 41 -1/02

37

• Fuel timing control

• Inputs to timingcontrol

• Benefits of a "smart"timing control

EUI CONTROL LOGIC

ENGINE SPEED

FUEL QUANTITY FUEL RPM

COLD MODE

SELECTTIMING

CONVERTDESIREDTIMING

COOLANTTEMPERATURE

TIMING CONTROL

DEGREES BTDC DESIREDTIMINGBTDC

TIMINGFUEL INJECTION

TIMING WAVE FORM

Fuel Injection Control System

This diagram shows the timing control logic within the ECM.

Engine speed and fuel quantity (which relates to load) inputs are receivedby the timing control. These combined inputs determine the start of fuelinjection.

The timing control provides the optimum timing for all conditions. Thebenefits of a "smart" timing control are:

- Reduced particulates and lower emissions

- Improved fuel consumption while still maintaining performance

- Extended engine life

- Improved cold starting

STMG 681 - 42 -1/02

38

• Fuel quantity control

• Inputs to fuel quantitycontrol

• Start of injectiondetermines timing

• Injection durationdetermines fuelquantity

ELECTRONICGOVERNOR

TORQUEMAPS

FRCMAPS

TURBO OUTLET ANDATMOSPHERIC

PRESSURE SENSORS

ENGINECONTROL

LOGIC

THROTTLE

SHUTDOWNS

ENGINE RPM

TDC

87654321

SIGNALSTO FUEL

INJECTORS

FUELINJECTIONCONTROL

SPEED/TIMINGSIGNAL

ENGINE RPM

SPEED/TIMINGSENSOR

TIMINGWHEEL

ENGINE RPM

ECM

COOLANTTEMPERATURE

SENSOR

3500BELECTRONIC GOVERNOR

Three inputs control fuel quantity:

1. Engine speed

2. Throttle position

3. Boost

These signals are received by the electronic governor portion of the ECM. The governor then sends the desired fuel signal to the fuel injectioncontrol. The electronic governor also receives signals from the fuel ratiocontrol and torque control.

Two variables determine fuel quantity and timing:

- The start of injection determines engine timing.

- The injection duration determines the quantity of fuel to be injected.

STMG 681 - 43 -1/02

39

• Speed/timing sensor

• Three functions ofspeed/timing sensor

• Sensor installation

P20/J20SPEED/TIMING SENSOR MACHINE INTERFACE

CONNECTOR

COOLANTTEMPERATURE SENSOR

8/12/16INJECTORS

GROUND BOLT


J2

J1

ECM

UNFILTERED OILPRESSURE SENSOR

CRANKCASEPRESSURE SENSOR

ATMOSPHERICPRESSURE SENSOR

TURBOCHARGER OUTLETPRESSURE SENSOR

FILTERED OILPRESSURE SENSOR

RIGHT TURBOCHARGERINLET PRESSURE SENSOR

LEFT TURBOCHARGERINLET PRESSURE SENSOR

AFTERCOOLERTEMPERATURE SENSOR

LOW OILLEVEL SWITCH


PRESSURE SWITCH

COOLANTFLOW SWITCH

LEFT TURBOCHARGEREXHAUST

TEMPERATURE SENSOR

RIGHT TURBOCHARGEREXHAUST

TEMPERATURE SENSOR

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

P31/J31 J25/P25

J28/P28

J22/P22

J23/P23

J27/P27

J29/P29

J48/P48

J3/P3

P26T/C CONNECTOR

BASIC ENGINE BLOCK DIAGRAM

The Speed/Timing Sensor serves three basic functions in the system:

1. Engine speed measurement

2. Engine timing measurement

3. Cylinder identification and TDC location

The Speed/Timing Sensor is mounted on the rear housing below thetiming wheel. This sensor is self-adjusting during installation and haszero clearance with the timing wheel.

The sensor head is extended prior to installation. The action of screwingin the sensor pushes the sensor head back into the body when the headcontacts the timing wheel. This contact is momentary while the engine isstarting. After initial start-up, the head runs with zero clearance.

STMG 681 - 44 -1/02

40

• Speed/timing sensor

• Power supply

3229381812

996-GN998-BR999-WHF723-PKF724-PU

+V TIMINGDIGITAL RETURNPRIMARY ENGINE SPEEDTIMING CAL +TIMING CAL -

ECM

P2 J2

ABC

ORBKWH

SPEED/TIMINGSENSOR

TIMING CALIBRATIONCONNECTOR

12

SPEED/TIMING SENSOR

P20 J20

P26 P1 J1

The Speed/Timing Sensor (left rear of engine) measures engine speed forgoverning and crankshaft position for timing purposes and cylinderidentification.

The ECM supplies 12.5 ± 1 Volts to the Speed/Timing Sensor.

Connector pins A and B transmit the common power supply to the sensor.The C connector pin transmits the signals from the sensor to the ECM.

NOTE: The Speed/Timing Sensor has a dedicated power supply. Noother circuits should be spliced into this power supply.

• Timing wheel andspeed/timing sensor

41

The Timing Wheel is indexed with a drilled hole which is mated to adowel on the camshaft. This dowel locates the wheel in the correctposition on the camshaft relative to the crankshaft.

As previously stated, the Timing Wheel has a total of 24 teeth. 21 teethare large with small spaces between them (80/20 relative size). The otherthree teeth and spaces have equal dimensions (50/50 relative size). Thisconfiguration is used by the ECM as a reference point for determining theposition of the engine for fuel timing.

The Speed/Timing Sensor can identify the equal size teeth because theycreate a different signal pattern than the other teeth.

NOTICE

The head of the sensor MUST NOT be positioned in the wide timingwheel slots during installation. Incorrect positioning will causedamage to the sensor head.

STMG 681 - 45 -1/02

STMG 681 - 46 -1/02

42

• Sensor generates aPWM signal fromtiming wheel teeth

50/50TOOTHSLOT

50/50TOOTHSLOT

50/50TOOTHSLOT

80/20TOOTHSLOT

SPEED/TIMINGSENSOR

TIMINGCALIBRATION

RANGE ± 7°

CYL. NO. 3REFTDC

CYL. NO. 4

REF

TDCCYL. NO. 8

TDC

REF

The Speed/Timing Sensor is positioned over the circumference of theteeth.

The teeth and sensor generate a Pulse Width Modulated (PWM) signal forthe purpose of timing and a frequency modulated output for speedmeasurement.

INSTRUCTOR NOTE: A description of PWM signals is providedlater in this presentation.

STMG 681 - 47 -1/02

43

• Cranking

• Timing wheel teethand spacing

TIMING GEAR TOOTH TABLETABLEENTRY

CYLINDERREFERENCE

ABCDEFGH

80 %50 %80 %80 %80 %50 %50 %80 %

NONE IDENTIFIED

PWM DUTYCYCLE

A B C D E F G H

TIMING WHEEL ROTATION

CRANKING

80/20 % 80/20 % 80/20 %80/20 %50/50% 50/50% 50/50%

The Speed/Timing Sensor uses the timing wheel with the teeth arrangedas shown to initially determine:

- Top Dead Center No. 1 (When found, the cylinders can beidentified.)

- Engine speed

The sequence of signals shown in the second column (PWM duty cycle) isanalyzed by the ECM. At this point, no fuel will be injected until certainconditions have been met.

STMG 681 - 48 -1/02

44

• After patternrecognition

• Initial firing sequence

CYL. NO. 1REFERENCE

EDGE

TIMING GEAR TOOTH TABLE

CYLINDERREFERENCE

80 %50 %80 %80 %80 %50 %50 %80 %

NOCYL. NO. 1NONOCYL. NO. 2NONOCYL. NO. 7

TABLEENTRY

ABCDEFGH

PWM DUTYCYCLE AFTER PATTERN RECOGNITION

A B C D E F G H


CYL. NO. 2TDC

CYL. NO. 2REFERENCE

EDGE

CYL NO. 1TDC

During start-up, the sensor initially monitors the pulses created by thepassing teeth and identifies the sequence as shown. After a completerotation, the control can recognize the location of TDC from the pattern inthe above illustration.

During initial cranking, no fuel is injected until:

- The Timing wheel has completed a revolution (the sensor has readthe three 50/50 teeth).

- TDC for all cylinders is identified by the control.

After the sensor has provided the necessary signals, the ECM is ready tostart injection.

NOTE: The reference points in the illustration are positions on thetiming wheel from which the control measures the point of injectionand TDC.

STMG 681 - 49 -1/02

45

• Normal operation

• Signal patternidentifies TDC

• Conditions forinjection

TIMING GEAR TOOTH TABLE

PWM DUTYCYCLE

CYLINDERREFERENCE

80 %50 %80 %80 %80 %50 %50 %80 %

NORMAL OPERATIONNOCYL. NO. 1NONOCYL. NO. 2NONOCYL. NO. 7

CYL. NO. 1REFERENCE

DES TIMING

DELAY

60° BTDC (EEPROM)

NO. 1INJECTION

ASSUMED TDC

CYL. NO. 1ACTUAL TDC

(CALIBRATED)

CYL. NO. 2REFERENCE

CYL. NO. 2ACTUAL TDC

(CALIBRATED)

60° BTDC (EEPROM)

TABLEENTRY

ABCDEFGH

A B C D E F G H


NO. 2INJECTION

DES TIMINGASSUMED

TDC

During normal operation, the ECM can determine timing (assumed TDC)from the cylinder reference point for each cylinder. The actual TDC isstored by the ECM after calibration is performed.

Injection timing is calibrated by connecting a TDC probe to the serviceaccess connector on the engine harness, and by activating the calibrationsequence with the Caterpillar ET service tool. The ECM raises the enginespeed to 800 rpm (to optimize measurement accuracy), compares theactual No. 1 TDC location to the assumed cylinder No. 1 TDC location,and saves the offset in the EEPROM (Electrically Erasable ProgrammableRead Only Memory).

NOTE: The calibration offset range is limited to ± 7 crankshaftdegrees. If the range is exceeded, the offset is set to zero (nocalibration) and a calibration diagnostic message is generated.

STMG 681 - 50 -1/02

46

• Timing calibrationsensor

3229381812

996-GN998-BR999-WHF723-PKF724-PU

+V TIMINGDIGITAL RETURNPRIMARY ENGINE SPEEDTIMING CAL +TIMING CAL -

ECM

P2 J2

ABC

ORBKWH

SPEED/TIMINGSENSOR

TIMING CALIBRATIONCONNECTOR

P26

TIMING CALIBRATIONSENSOR

TIMING CALIBRATION SENSOR

P20 J20

P1 J1

12

The Timing Calibration Sensor (magnetic pickup) is installed in theflywheel housing during calibration. The connector is located above theECM. (On some machines, i.e. D11 Tractor, the sensor is permanentlyinstalled.)

Using the Caterpillar ET service tool, timing calibration is accomplishedautomatically for both sensors when selected on the appropriate screen.

The desired engine speed is set to 800 rpm. This rpm setting is performedto avoid instability and ensure that no backlash is present in the timinggears during the calibration process. Also, the system has a repeatablepoint for improved calibration accuracy.

STMG 681 - 51 -1/02

47

• Timing calibration

• Corrects smallcrankshaft to timinggear tolerances

• Calibration offsetrange ± 7 degrees

REFERENCE EDGE TO TDC DISTANCE

REFERENCEEDGE ASSUMED

CYL. NO. 1 TDCACTUAL

CYL. NO. 1 TDC

TIMINGREFERENCE

OFFSET

MAXIMUM TIMING REFERENCE OFFSET ± 7 DEGREES

TIMING CALIBRATIONSENSOR SIGNAL

TIMINGWHEEL

TIMING CALIBRATION

± 7 °

-7° +7°

As the Speed/Timing Sensor uses the timing wheel for a timing reference,timing calibration improves fuel injection accuracy by correcting for anyslight tolerances between the crankshaft, timing gears and timing wheel.

During calibration, the offset is saved in the ECM EEPROM (ElectricallyErasable Programmable Read Only Memory). The calibration offsetrange is limited to ± 7 crankshaft degrees. If the timing is out of range,calibration is aborted. The previous value will be retained and adiagnostic message will be logged.

The timing must be calibrated after performing the following procedures:

1. ECM replacement

2. Speed/timing sensor replacement

3. Timing wheel replacement

4. Camshaft, crankshaft or gear train replacement

• Unit injector currentflow

48

This illustration shows how the current increases initially to pull in theinjection coil and close the poppet valve. Then, by rapidly chopping(pulsing) the 105 Volts on and off, current flow is maintained. The end ofinjection occurs when the current supply is cut off and fuel pressure dropsrapidly in the injector.

INSTRUCTOR NOTE: This waveform may be demonstrated with a9U7330 Digital Multimeter (or equivalent) and a current probe.

STMG 681 - 52 -1/02

0 1 2 3 4

CU

RR

EN

T F

LO

W

TIME (MILLISECONDS)

5

PULL-IN PEAK CURRENT

HOLD-IN PEAK CURRENT

INJECTION CURRENT WAVEFORMONE CYCLE

• Cold modes

• Cold mode cylindercutout

49

The EUI fuel system is designed to modify its operational characteristicsduring cold conditions. This modification is done to protect theenvironment and to improve the operational characteristics of the engine.

A feature which was introduced with the 3500B is the Cold Mode Cutout.This feature activates when the engine is at low speed, load andtemperature. As each individual cylinder is cut out, the ECM looks at thefuel rate measurement. If the fuel rate does not increase, the ECMassumes that this cylinder is not firing.

To protect the dead cylinder from the effects of fuel washing down thepiston and liner, the ECM leaves the cylinder in the cutout condition. TheECM now goes to the No. 2 cylinder and repeats the process. After thelast cylinder is checked, the ECM goes to cylinder No. 1 and starts again.

The engine may appear to misfire during the process, but this condition isnormal. Checking the active faults with the engine running will verifythat no electrical faults are present.

This function is turned off when the throttle is opened more than 25%,coolant temperature is above 60°C or if the engine speed is above 1300 rpm.

INSTRUCTOR NOTE: The various cold modes are tabulated inServiceman's Handout No. 4.

STMG 681 - 53 -1/02

• Speed Control• Fuel Limiting• Injection Timing

• Ether Injection• Injector Cold Mode Cutout

FUEL SYSTEM COLD MODES

• Fuel system limits

• Variable horsepower

• Economy shift mode

50

Just as earlier engines had mechanical limits to determine maximum fueldelivery during full load, full torque and acceleration, the EUI system haselectronic limits to protect the engine. These limits are:

- Maximum Horsepower

- Torque Limit (Determines torque rise characteristics)

- Fuel Ratio Control (Limits fuel until sufficient boost is available)

- Cold Mode Limit (Limits fuel with cold engine to control whitesmoke)

- Cranking Fuel Limit (Limits fuel during cranking)

An acceleration delay during start-up holds the engine at low idle for twoseconds or until the oil pressure reaches 140 kPa (20 psi).

Off-highway Trucks have a system which increases engine horsepower indirect drive only. This system protects the drive line from excessivetorque in the lower gears. The feature can be overridden with ET whendynamometer testing.

Off-highway Trucks also have a service tool programmable feature whichis designed to lower shift points and the fuel limit to improve fuelconsumption at the customer's request.

STMG 681 - 54 -1/02

FUEL SYSTEM LIMITS

• Cranking Fuel Limit

• Cold Mode Limit

• Fuel Ratio

• Maximum Torque

• Maximum Horsepower

• Fuel system derates

51

As the system limits fuel for every condition, derates are also built intothe system for protection. These derates are individually covered later inthe presentation, but are summarized here:

- Automatic Altitude Compensation (Altitude derate)

- Automatic Filter Compensation (Derates for air filter restriction ifinstalled)

- Engine Warning Derate for the following conditions:

Low oil pressure

High coolant temperature

High exhaust temperature

High and low boost

If a loss of boost sensor output occurs, the ECM assumes zero boostpressure. Although not strictly a derate, power is reduced byapproximately 50 to 60%.

STMG 681 - 55 -1/02

FUEL SYSTEM DERATES

• Automatic Altitude Compensation

• Automatic Filter Compensation

• High and Low Boost Derate

• Engine Warning Derate

INSTRUCTOR NOTE: This material will be reinforced if thefollowing ET tasks are demonstrated. Review the material withquestions following the tasks. The demonstration can be performedon an engine or machine with a laptop computer. The suggestedtopics are:

Basic ET review (if required)

Status screens with all appropriate parameters

Active diagnostic codes

Logged diagnostic codes

Events screen and overspeed histogram

Configuration screen

Timing calibration

Injector solenoid test

Cylinder cutout test

Automatic injector test

Program injector codes

Air fuel ratio control setting (read and change)

STMG 681 - 56 -1/02

52

FUEL SUPPLY SYSTEM

This portion of the presentation describes the operation of the EUI FuelSupply System as used on the 3500B engines in machine applications.

STMG 681 - 57 -1/02

FUEL SUPPLY SYSTEM

STMG 681 - 58 -1/02

53

• Fuel supply circuit

FUEL TANK

PRIMARYFUEL

FILTER


(2 MICRON)

ENGINEBLOCK

OIL RENEWALINJECTOR

FUELPRESSURE

REGULATOR

FUELTRANSFER

PUMPFUELHEATER

ECM

3516B FUEL SUPPLY CIRCUIT (793C)

PRIMING PUMP SUPPLY

FUELDIFFERENTIAL

PRESSURESWITCH

CYLINDERHEAD

ENGINEBLOCK

Fuel Supply Circuit

The system illustrated is for a 3516B in the 793C truck. Other systemsmay vary according to the application.

Fuel is drawn from the tank through a fuel heater (if equipped) andthrough the primary fuel filter to the fuel transfer pump. Fuel from thetransfer pump flows through the ECM for cooling purposes. From theECM, the fuel flows through the secondary fuel filters.

Fuel from the fuel filter base flows to the fuel injectors in the cylinderheads. Return fuel from the injectors flows through the fuel pressureregulator and the fuel heater before returning to the fuel tank.

The fuel heater utilizes the hot return fuel from the engine to heat theincoming fuel passing through the filters. The heater prevents plugging ofthe filters in extremely cold conditions.

➥

• Oil renewal system

• Two micronsecondary filters

The Oil Renewal System is controlled by the engine ECM. A smallamount of engine oil flows from the engine block to the oil renewalinjector manifold. The oil flows from the oil renewal injector manifoldinto the return side of the fuel pressure regulator. The engine oil mixeswith the fuel in the return line. It then flows to the tank. The combinedoil and fuel mixture circulates back to the injectors to be burned with thefuel. It should be noted, however, that the ratio of oil to fuel is quite low.

This circuit is more fully described later under Application SpecificSystems.

NOTICE

All current 3500 engines are equipped with two micron secondaryfilters. This requirement is common with most high pressure fuelsystems. Failure to meet the two micron filter requirement will resultin less than expected life for the injectors.

INSTRUCTOR NOTE: Refer to Serviceman's Handout No. 6 whendiscussing the two micron filter requirement.

STMG 681 - 59 -1/02

• Fuel systemcomponents:

1. Transfer pump

2. Bypass valve

54

Fuel Supply Components

The fuel transfer pump (1) is driven by the front gear train.

The fuel transfer pump contains a bypass valve (2) to protect the fuelsystem components from excessive pressure. The bypass valve setting ishigher than the setting of the fuel pressure regulator (next slide).

Fuel flows from the transfer pump through the ECM and the secondaryfuel filters located on the left side of the engine.

STMG 681 - 60 -1/02

1

2

• Fuel systemcomponents:

1. Steel tubes


• Fuel pressure testpoint

55

Fuel flows from the fuel filter base through the steel tubes (1) to the fuelinjectors. Return fuel from the injectors flows through the Fuel PressureRegulator (2) before returning to the fuel tank.

Fuel system pressure is controlled by the Fuel Pressure Regulator. Thisvalve is set at 415 to 450 kPa (60 to 65 psi).

The valve is positioned downstream of the fluid manifold fuel passagesand the injectors. Fuel which passes through the valve is returned to thefuel tank. The fuel lines from both fuel passages in the manifolds arejoined at the regulating valve.

Fuel pressure can be checked at the Fuel Pressure Regulator Valve byremoving a plug and connecting a gauge.

STMG 681 - 61 -1/02

1 2

STMG 681 - 62 -1/02

56

• MUI and EUIinstallationdifferences

MUI EUI

CYLINDER HEADSMUI AND EUI

This slide shows the difference between the Mechanical Unit Injection(MUI) and current Electronic Unit Injection (EUI) installation in thecylinder head.

Notice the Helper Spring on the injector pushrod. This arrangement isdesigned to keep the follower in constant contact with the camshaft. Thehelper spring is required due to the increased injection pressures of 151 MPa (22,000 psi) and the steeper, high lift camshaft lobe profile.

STMG 681 - 63 -1/02

57

• Unit injector fuelsupply

PRIMARYFILTER

TRANSFERPUMP

SECONDARYFILTER

FUEL TANK

ELECTRONICUNIT INJECTOR

ECM

FUELTANK

FUELPRESSURE

REGULATOR

This view shows the injector and its fuel supply circuit. A larger volumeof fuel passes through the injector than is required for injection. Thisextra flow is used to cool the injector, which is also surrounded bycoolant.

INSTRUCTOR NOTE: To reinforce this presentation, the followingtasks may be demonstrated on an engine using the Service Manualprocedures:

Remove and install a unit injector.

Perform the necessary timing adjustments.

Prime the fuel system.

Using the ET, perform an Injector Solenoid Test and CylinderCutout Test.

Check for active and logged faults.

• Six system powersupplies

58

SYSTEM POWER SUPPLIES

The 3500B EUI system has one external and five internal power supplieswith various voltages as shown.

EXTERNAL POWER SUPPLIES

ECM power supply 24 Volts

INTERNAL POWER SUPPLIES

Speed/Timing Sensor power supply 12.5 Volts

Injector power supply 105 Volts

Analog Sensor power supply 5 Volts

Digital Sensor power supply 8 Volts

Wastegate Control Solenoid power supply 0 - 24 Volts

The power supplies are described in detail in the following section.

STMG 681 - 64 -1/02

3500B SYSTEM POWER SUPPLIES

• ECM: 24 VOLTS

• INJECTORS: 105 VOLTS

• ANALOG SENSORS: 5 VOLTS

• SPEED/TIMING SENSORS: 12.5 VOLTS

• DIGITAL SENSORS: 8 VOLTS

• WASTEGATE CONTROL SOLENOID: 0 - 24 VOLTS

STMG 681 - 65 -1/02

59

• 24 Volt power supply

• Power supplycomponents

GROUNDBOLT

(FRAME)

15 AMPBREAKER

24 VJ3/P3 MACHINE

INTERFACECONNECTOR8/12/16

INJECTORS

GROUND BOLT (ENGINE)

P26 T/C CONNECTOR


J2

J1

ECM

BATTERY

113-OR


DISCONNECTSWITCH

KEY STARTSWITCH

ECM POWER SUPPLY BLOCK DIAGRAM

ECM Power Supply

The power supply to the ECM and the system is drawn from the 24-Voltmachine battery. The principle components in this circuit are:

- Battery- Key Start Switch- Main Power Relay- 15 Amp Breaker- Ground Bolt- ECM Connector (P1/JI)- Machine Interface Connector (J3/P3)

If the supply voltage exceeds 32.5 Volts or is less than 9.0 Volts, adiagnostic code is logged. (See the Troubleshooting Guide for completedetails on voltage event logging.)

NOTE: The Ground Bolt and the Machine Interface Connector arethe only power supply components mounted on the engine.

STMG 681 - 66 -1/02

60

• ECM power supplycircuit

0511040623

ECM

(-) BATTERY(+) BATTERY

KEY SWITCH ON

229-BK-14229-BK-14150-RD-14150-RD-14 113-OR

24 VOLTS DC

(+)

(-)

ENGINE BLOCKGROUND BOLT

BREAKER

ENGINE BATTERYAND CHARGING

SYSTEM

R

CSB ST

OFF

308-YL

200-BK

105-RD

KEY START SWITCH

112-PU

117-RD

113-OR

15 A

10 AMP

P1 J1

ECM POWER SUPPLY CIRCUIT

MACHINE INTERFACECONNECTOR

12

26P3 J3

This schematic shows the principle components for a typical 3500B ECMpower supply circuit. Battery voltage is normally connected to the ECM.However, an input from the key start switch turns on the ECM. Batteryvoltage may be checked using the service tool status screen.

The machine wiring harness can be bypassed for troubleshootingpurposes. These steps are described in the Troubleshooting Procedure.

Notice the P1/JI and P3/J3 connectors in the circuit (described on the nextslide.)

INSTRUCTOR NOTE: The power supply cables are paired betweenthe battery and the ECM to reduce resistance.

Not all connectors are shown between the machine interfaceconnector and the 15 amp breaker. Refer to the machine electricalschematic for complete details.

STMG 681 - 67 -1/02

61

• J1/J2 40 pinconnectors

• J3/P3 40 pinconnector

7

13

19

23

29

12

18

22

28

34

1 2 3 4 5 6

35 36 37 38 39 40

7

13

19

23

29

12

18

22

28

34

1 2 3 4 5 6

35 36 37 38 39 40

ECM CONNECTORS40 PINS, WIRE SIDE

P2 P1

A common but vital part of all the power supplies (and sensor circuits)described to this point is the 40 pin connector.

This slide shows the two ECM 40 pin connectors, P1 and P2, lookingfrom the wire side. The pins highlighted in the P1 connector are for theECM power supply circuit.

The system also includes the J3/P3, 40 pin Machine Interface Connector.This 40 pin connector transmits the power supply from the machinewiring to the engine wiring harnesses.

The Troubleshooting Guide identifies the relevant pins for each circuit inthis manner. The J3/P3 connector is identified identically and is also apart of the system power supply.

STMG 681 - 68 -1/02

62

• 12.5 Volt powersupply from ECM

3229381812

996-GN998-BR999-WH

+V TIMINGDIGITAL RETURNENGINE SPEEDTIMING CAL +TIMING CAL -

ECM

P2 J2

ABC

ORBKWH

SPEED/TIMINGSENSOR

SPEED/TIMING SENSOR POWER SUPPLY12.5 ± 1 VOLTS

P20 J20

P1 J1

Speed/Timing Sensor Power Supply

The Speed/Timing Sensor has a dedicated power supply. The ECMsupplies 12.5 ± 1 Volts to the Speed/Timing Sensor.

Connectors A and B send the common power supply to the sensor. The C wire transmits a separate signal to the ECM.

This power supply is not battery voltage, but is generated and regulatedwithin 1.0 Volt by the ECM. This power supply and the Speed/TimingSensor are vital parts of the EUI system. A failure of the sensor willresult in an engine shutdown.

NOTICE

Connecting another system or accessory to the Speed/Timing Sensorpower supply will cause an engine malfunction or failure.

STMG 681 - 69 -1/02

63


160532

A701-GYF726-YLA703-BRF726-YL

P2 J2

3512B INJECTOR WIRING SCHEMATIC

SOLENOID 1 POWERSOLENOID 1/3 RETURNSOLENOID 3 POWER

ECM

401134

A702-PUF727-BUA704-GNF727-BU


321738

A705-BUF728-BRA707-PUF728-BR


282122

A706-GYF729-GNA708-BRF729-GN


372731

A709-ORF730-GYA711-PUF730-GY


183312

A710-GYF731-ORA712-BRF731-OR


SOL 1

SOL 3

J52/P52

SOL 2

SOL 4

J56/P56

SOL 5

SOL 7

J53/P53

SOL 6

SOL 8

J57/P57

SOL 9

SOL 11

J54/P54

1234

SOL 10

SOL 12

J58/P58

INJECTORSOLENOIDS

1234

1234

1234

1234

1234

Injector Power Supplies

The injectors are supplied with power from the ECM at 105 Volts. Forthis reason, precautions must be observed when performing maintenancearound the valve covers.

On the 3512B and 3516B, two of the internal power supplies are used forthe injectors. If a failure occurs, only one bank of injectors could havefailed. On the 3508B, only one of the internal power supplies is used. Aspreviously mentioned, the same ECM is used on all three configurations.

If an open or a short occurs in the injector circuit, the ECM will disablethat injector. The ECM will periodically try to actuate that injector todetermine if the fault is still present and will disconnect or reconnect theinjector as appropriate.

STMG 681 - 70 -1/02

64

• Provides power to allanalog sensors


• Power supplyprotected againstshort circuits

P22 J22

ENGINE COOLANTTEMPERATURE SENSOR

FILTERED OILPRESSURE SENSOR

+V ANALOGANALOG RETURNSIGNAL


P23 J23

TURBO OUTLETPRESSURE SENSOR


P25 J25

RIGHT TURBO INLET PRESSURE SENSOR


P27 J27

ATMOSPHERICPRESSURE SENSOR


P28 J28

LEFT TURBO INLETPRESSURE SENSOR


3630

3500B ANALOG SENSORPOWER SUPPLY

P1 J1

P43 J43


CRANKCASEPRESSURE SENSOR

P48 J48


UNFILTERED OILPRESSURE SENSOR

ABC

ABC

ABC

ABC

ABC

ABC

ABC

J21 P21

5 ± 0.5 VOLTS

+V ANALOG SUPPLYANALOG RETURN

ECM

ABC

Analog Sensor Power Supply

The Analog Sensor Power Supply provides power to all the analogsensors (pressure and temperature).

The ECM supplies 5.0 ± 0.5 Volts DC (Analog Supply) through the J1/P1connector to each sensor.

A power supply failure will cause all analog sensors to appear to fail.

The power supply is protected against short circuits, which means that ashort in a sensor or a wiring harness will not cause damage to the ECM.

STMG 681 - 71 -1/02

65


• Power supplyprotected againstshort circuits

+ V DIGITAL SUPPLY- V DIGITAL RETURN

2935

DIGITAL SENSORPOWER SUPPLY

P1 J1

ABC

J31 P31+V DIGITAL

DIGITAL RETURNSIGNAL

RIGHT EXHAUST TEMPERATURE SENSOR

ABC

J35 P35THROTTLE

POSITION SENSOR+V DIGITAL


8 ± 0.5 VOLTS

ABC

J30 P30+V DIGITAL


LEFT EXHAUST TEMPERATURE SENSOR

ABC

J84 P84+V DIGITAL


FAN SPEED SENSOR

ECM

Digital Sensor Power Supply

The ECM supplies power at 8 ± 0.5 Volts through the J1/P1 connector tothe following circuits:

- Throttle Position Sensor

- Fan Speed Sensor (if installed)

- Exhaust Temperature Sensors

The power supply is protected against short circuits, which means that ashort in a sensor will not cause damage to the ECM.

STMG 681 - 72 -1/02

66

• Valve operation testedwith ET

• Valve position readwith ET

WASTEGATE CONTROLPWM DRIVER & SOLENOID RETURN

2935

P2 J2

AB

J41 P41

WASTEGATE CONTROLSOLENOID VALVE

SUPPLY RETURN

WASTEGATE CONTROL SOLENOIDPOWER SUPPLY0 TO 1.04 Amps PWM

ECM

Wastegate Control Solenoid Power Supply

The ECM supplies a PWM signal of 0 to 1.04 amps through the J2/P2connector to the Wastegate Control Solenoid Valve.

The solenoid valve and power supply can be tested on the engine usingET and the Wastegate Position Test. Using the test, the pressure can beadjusted manually with the ET service tool from minimum to maximum.Therefore, this function can be used to verify the operation of the ECM,the power supply and the control valve.

The service tool status screen "Wastegate Position" reading can be used toshow the position with 0% indicating the closed position and minimumcurrent used, and 100% indicating fully opened with the maximum currentused. This measurement can be used in conjunction with the desired andactual boost pressures to check the system operation.

➥

INSTRUCTOR NOTE: The following exercise will reinforce thematerial introduced in the preceding slides and will allow questions tobe answered.

During this exercise, a demonstration on an engine or a Training Aidshould be performed showing:

Open circuit in the ECM power supply

Opens and shorts in the Speed/Timing sensor power supply

Opens and shorts in the Analog and Digital power supplies

Status screen pressure and temperature readings with a fault inthe sensor power supply

STMG 681 - 73 -1/02

67

ELECTRONIC SENSORS AND SYSTEMS

This section of the presentation covers the electronic sensors and relatedcircuits for 3500B EUI fuel systems used in machine applications.

STMG 681 - 74 -1/02

3500B ELECTRONIC

SENSORS AND SYSTEMS

STMG 681 - 75 -1/02

68

• Engine and machinewiring block diagrams

TOPRELUBRICATION

PUMP

+ BATTERY

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35





GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY


A/C ONSWITCH

FAN SPEED SENSOR

+ BATTERY

RELAYCYLINDER

ENGINE

ETHER START VALVE

STARTINGAID SWITCH

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

J27/P27

J48/P48

P84/J84

P41/J41

308-YL

113-OR



DISCONNECTSWITCH


15 AMPBREAKER

COOLANTTEMPERATURE

SENSOR


RELAY

J21/P21

J47/P47

J103/P103

J113/P113

P31/J31


This block diagram shows all the electrical circuits on the engine and themachine (Off-highway Truck). The engine circuits will be described first,followed by the machine circuits.

On the diagram, the dashed lines divide the engine mounted circuits andthe machine mounted circuits.

STMG 681 - 76 -1/02

69

• Four functions of thespeed/timing sensor

• Self-adjusting zerogap sensor

P20/J20SPEED/TIMING

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM

SPEED/TIMING SENSOR

Speed/Timing Sensing Circuit

One Speed/Timing Sensor is installed and a serves four basic functions inthe system:

- Engine speed detection

- Engine timing detection

- Cylinder and TDC identification

- Reverse rotation protection

The Speed/Timing Sensor is mounted on the rear housing and is self-adjusting during installation.

➥

• No air gap

• Use status screen tocheck output

• Dedicated powersupply

• Sensor installationprecautions

• Calibration requiredafter theseprocedures

This type of sensor does not have a typical fixed air gap. However, thesensor is not in direct contact with the timing wheel, but does run withzero clearance. A Speed/Timing Sensor failure will cause an engineshutdown.

The sensor may be functionally checked by cranking the engine andobserving the service tool status screen for engine rpm.

A sensor failure will be indicated by the active fault screen on the servicetool. An intermittent failure will be shown in the logged fault screen.

The sensor has a dedicated power supply. A power supply failure at theECM will cause the sensor to fail.

The sensor head is extended prior to installation. The action of screwingin the sensor pushes the head back into the body after the head contactsthe timing wheel.

During installation, it is essential to check that the sensor head is notaligned with a wide slot in the timing wheel. If this condition occurs, thehead will be severed when the engine is started, and some disassemblymay be necessary to remove the debris.

As mentioned earlier, timing calibration is normally performed after thefollowing procedures:

1. ECM replacement

2. Speed/timing sensor replacement

3. Engine timing adjustment

4. Camshaft, crankshaft or gear train replacement

STMG 681 - 77 -1/02

70

Analog Sensors and Circuits

The following analog sensors may be used in various applications:

- Coolant Temperature Sensor

- Aftercooler Temperature Sensor

- Oil Pressure Sensors (2)

- Atmospheric Pressure Sensor

- Turbocharger Inlet Pressure Sensors (1 or 2)

- Turbocharger Outlet (Boost) Sensor

- Crankcase Pressure Sensor

STMG 681 - 78 -1/02

ANALOG SENSORS

• Aftercooler temperature sensor

• Oil pressure sensors

• Turbocharger outlet (boost) sensor

• Turbocharger inlet pressure sensors

• Atmospheric pressure sensor

• Coolant temperature sensor

• Crankcase pressure sensor

STMG 681 - 79 -1/02

71

• Coolant temperaturesensor

• Sensor functions

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTORJ4/P4 THROUGH

J19/P19

J2

J1

ECM

J21/P21

COOLANT TEMPERATURE SENSOR

The Coolant Temperature Sensor supplies the temperature signal for thefollowing functions:

- Caterpillar Monitoring System or VIMS instrument display, warninglamps and alarm

- Demand Control Fan (if so equipped)

- ET coolant temperature display

- High coolant temperature event logged above 107°C (225°F)

- Engine Warning Derate when 107°C (225°F) is exceeded or low oilpressure occurs (if so equipped)

- Reference temperature for Cold Mode operation

NOTE: All analog sensors use the common analog power supply of5.0 ± 0.2 Volts.

STMG 681 - 80 -1/02

72

• Aftercoolertemperature sensor

• Fan control referencetemperature

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR

J21/P21

J32/P32

AFTERCOOLER TEMPERATURE SENSOR

The Aftercooler Temperature Sensor is mounted at the rear of the block(Off-highway Truck) and measures coolant temperature in the aftercoolercircuit.

The ECM uses the sensor signal as a reference for the fan control. Whenhigh aftercooler temperatures are reached, the cooling fan speed isincreased. Very high aftercooler temperatures will cause a VIMS warningevent to be logged.

NOTE: This sensor measures the ability of the aftercooler to cool theair sufficiently for combustion. As a general rule, for every 1 degreethat the combustion air is reduced in temperature, the exhaust will bereduced by approximately 3 degrees. High inlet manifoldtemperatures can significantly shorten the life of exhaust systemcomponents (i.e. exhaust manifolds, valves, turbochargers andpistons). High temperatures will cause a loss of power also.

STMG 681 - 81 -1/02

73

• Oil pressure sensors

• Oil pressure sensorscombined to measurefilter restriction

OIL PRESSURE SENSORS

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT


J2

J1

ECM


SENSOR


SENSOR


SENSOR

J22/P22

J21/P21

J32/P32

J48/P48

T/CCONNECTOR

P26

Three pressure sensors are used for the measurement of oil pressure:

- Two Oil Pressure Sensors (filtered and unfiltered)

- Atmospheric Pressure Sensor

The filtered and unfiltered pressure sensors are used together to measureoil filter restriction.

The filtered oil pressure sensor is used to measure lubrication oil pressurefor the operator on the dash panel and for the technician on ET. Theatmospheric pressure sensor is used with this oil pressure sensor tocalculate the gauge pressure reading.

➥

LUBRICATION OIL PRESSURE CALCULATIONS

MEASUREMENT MEASURED BY RESULT

Oil pressure [oil press (A) - atmospheric (A)] = Oil pressure (GP)

Oil filter restriction [Unfiltered oil press - Filtered oil press] = Differential pressure (∆P)

These measurements are used to determine oil pressure for the ET service tool and for the dash displayto alert the operator that an abnormal condition exists. The sensor operating range is 0 to 1000 kPa (0 to 144 psi) (A).

Two lubrication oil pressure sensors are installed on this engine. One sensor measures pressure beforethe oil filter, and the other sensor measures pressure after the filter. These sensors are used together tocalculate oil filter restriction (∆P).

NOTE:

(A) = absolute pressure

(GP) = gauge pressure

(∆P) = differential pressure

INSTRUCTOR NOTE: Refer to Serviceman's Handout No. 5 for a complete list of ECMcalculations.

STMG 681 - 82 -1/02

STMG 681 - 83 -1/02

74

• Oil pressure map

• Determines correctpressure for all rpm

OIL

PR

ES

SU

RE

IN k

Pa

600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 180060

80

100

120

140

160

180

200

220

240

260

280

300

ENGINE RPM

OIL PRESSURE MAP

1900

320

340

8.7

11.6

14.5

17.4

20.3

23.2

26.1

29

31.9

34.8

37.7

40.6

43.5

46.4

49.3

OIL

PR

ES

SU

RE

IN P

SI

kPa x 0.145 = PSI

2000

Engine oil pressure varies with engine speed. As long as oil pressureincreases above the upper line after the engine has been started and isrunning at low idle, the ECM reads adequate oil pressure. No faults areindicated and no logged event is generated. A delay (de-bounce time)built into the system prevents false events from being logged after start-upor after a filter change.

If the engine oil pressure decreases below the lower line, the followingoccurs:

- An event is generated and logged in the permanent ECM memory.

- A Category 3 Warning (alert indicator, action lamp and alarm) isgenerated on the VIMS and Caterpillar Monitoring System.

- The engine is derated (if so equipped) to alert the operator.

The width of the pressure band between the two lines is sufficient toprevent multiple alarms and events or a flickering warning lamp. (Thispressure separation is referred to as hysteresis.)

• Low oil pressure tripsthese functions

STMG 681 - 84 -1/02

75

• Atmospheric pressuresensor

• Used to calculategauge pressure

• Two methods used tocalibrate sensors

• Four main functions

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS GROUND BOLT

P26


J2

J1

ECM


SENSOR


SENSOR

ATMOSPHERICPRESSURE

SENSOR


SENSOR

J22/P22

J21/P21

J32/P32

J27/P27

J48/P48

T/CCONNECTOR

ATMOSPHERIC PRESSURE SENSOR

All pressure measurements require the atmospheric pressure sensor tocalculate gauge pressure. All pressure sensors in the system measureabsolute pressure. The sensors are used individually in the case ofatmospheric pressure (absolute pressure measurement). They are used inpairs to calculate gauge pressures (oil and boost) and filter restriction.

All the pressure sensor outputs are matched to the Atmospheric PressureSensor output during calibration. Calibration can be accomplishedautomatically using the ET service tool or by turning on the key startswitch without starting the engine for five seconds. The AtmosphericPressure Sensor performs four main functions:

1. Automatic Altitude Compensation (Maximum derate 24%)

2. Automatic Filter Compensation (Maximum derate 20%)

3. Part of the pressure calculation for gauge pressure readings

4. Reference sensor for pressure sensor calibration

A foam filter is installed below the sensor to prevent the entry of dirt.

STMG 681 - 85 -1/02

76

• Automatic altitudecompensation

• System continuallyadjusts to optimumpower setting

100%

98%

96%

94%

92%

90%

88%

86%

84%

82%

80%

78%

76%

74%

77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53

8,210

8,920

9,630

10,340

11,050

11,760

12,470

13,890

14,600

15,310

16,020

16,730

17,440

13,180

7,500

72%

ENGINE POWER DERATING MAPACCORDING TO ATMOSPHERIC PRESSURE

ATMOSPHERIC PRESSURE IN kPa

PE

RC

EN

T O

F F

UL

L L

OA

D P

OW

ER

AL

TIT

UD

E IN

FE

ET

Atmospheric pressure measurement by the sensor provides an altitudereference for the purpose of Automatic Altitude Compensation.

The graph shown here describes how derating on a typical 3500B starts at7500 ft. and continues linearly to a maximum of 17000 ft. Other enginesmay start between 4000 and 12000 ft. depending on the application.

The advantage of the EUI system is that the engine always operates at thecorrect derating setting at all altitudes. The system continually adjusts tothe optimum setting regardless of altitude, so the engine will not exhibit alack of power or have smoke problems during climbs or descents todifferent altitudes.

NOTE: The EUI system has an advantage over a mechanical fuelsystem which is derated in "altitude blocks" (i.e. 7500 ft., 10000 ft.,12500 ft.). EUI derating is continuous and automatic. Therefore, amachine operating in the lower half of the block is not penalized withlow power. Conversely, a machine operating in the upper half of theblock will not overfuel with the EUI system.

STMG 681 - 86 -1/02

77

• Turbo inlet pressuresensor

• Sensors enableautomatic air filtercompensation

• Back-up to theatmospheric pressuresensor for altitude

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26


J2

J1

ECM


SENSOR


SENSOR


SENSOR

J25/P25

ATMOSPHERICPRESSURE

SENSOR


SENSOR

J22/P22


SENSOR

J28/P28

J21/P21

J32/P32

J27/P27

J48/P48

TURBOCHARGERINLET

PRESSURESENSORS

T/CCONNECTOR

The Turbocharger Inlet Pressure Sensor is used with the AtmosphericPressure Sensor to measure air filter restriction. This function is known asAutomatic Air Filter Compensation.

These two sensors are used to enable the Automatic Air FilterCompensation function by measuring the differential pressure across thefilter.

The Turbocharger Inlet Pressure Sensor is also used as a back-up to theAtmospheric Pressure Sensor for Automatic Altitude Compensation.

Depending on the inlet and air filter configuration, some applications mayhave two inlet pressure sensors (i.e. separate left and right systems withno connecting balance pipe).

STMG 681 - 87 -1/02

78

• Automatic filtercompensation

• Derating (typically)starts above 30 in. ∆P

CAT

AUTOMATIC AIR FILTER COMPENSATION

TURBOCHARGERINLET PRESSURE

SENSOR

ATMOSPHERICPRESSURE

SENSOR

Filter differential pressure calculated with formula:Atmospheric sensor pressure - Turbo sensor pressure = ∆PFuel limited 2% per 4 inches H20 to max 20%

Automatic Filter Compensation means that the engine is protectedagainst the effects of plugged filters. Derating is automatic as follows:

- Air filter restriction (∆P) exceeds 6.25 kPa (30 in. of water)

- Engine power derating starts at the rate of 2% per 1 kPa of ∆P

- Maximum derate 20%

- Event is logged when air filter restriction (∆P) exceeds 6.25 kPa(30 in. of water)

These ∆P specifications are typical examples. The actual values may varydepending on the application.

Derating is retained at the maximum ∆P until the key start switch iscycled off and on.

NOTE: If only one filter is plugged, the ET service tool andCaterpillar Monitoring System will display the highest ∆P of the two.Derating is also based on the highest ∆P of the two.

STMG 681 - 88 -1/02

79

• Turbocharger outletpressure sensor

• Air/fuel ratio control

• Air/fuel ratio control isadjustable with ET

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR


SENSOR

J25/P25

ATMOSPHERICPRESSURE

SENSOR

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23


SENSOR

J22/P22


SENSOR

J28/P28

J21/P21

J32/P32

J27/P27

J48/P48TURBOCHARGER

OUTLETPRESSURE

SENSOR

The Turbocharger Outlet Pressure Sensor measures absolute pressuredownstream of the aftercooler. Boost (gauge) pressure can be read withthe ET service tool. This measurement is a calculation using theAtmospheric Pressure and the Turbocharger Outlet Pressure Sensors.

A failure of this sensor will cause the ECM to default to a zero boostcondition. This failure can result in a 60% loss in engine power.

The function of the sensor is to enable the Air/Fuel Ratio Control whichreduces smoke, emissions and maintains engine response duringacceleration. The system utilizes manifold pressure and engine speed tocontrol the air/fuel ratio. Engine fuel delivery is limited according to amap of gauge turbo outlet pressure and engine speed.

The Air/Fuel Ratio Control setting is adjustable on 3500B machineapplications using the ET service tool.

STMG 681 - 89 -1/02

80

• Crankcase pressuresensor

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

ATMOSPHERICPRESSURE

SENSOR

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23


SENSOR

J22/P22


SENSOR

J28/P28

J21/P21

J32/P32

J27/P27

J48/P48

CRANKCASEPRESSURE

SENSOR

The ECM uses gauge pressure measured from the Crankcase PressureSensor and the Atmospheric Pressure Sensor to determine whethercrankcase pressure is excessive.

The ECM will warn the operator of possible damaging conditions andrecord adverse conditions in the memory.

A possible cause of excessive crankcase pressure could be piston damageor a piston ring failure. An early warning means that the engine can beshut down without catastrophic secondary damage.

Crankcase pressure (A) is compared with atmospheric pressure (A). Theresult is crankcase (gauge) pressure (i.e. pressure above ambient).

The trip points are:

WARNING 2 kPa (10 in. of water) EVENT 3.5 kPa (17in. of water)

• Trip points

STMG 681 - 90 -1/02

81

• Low oil level switch

• Filter differentialpressure switch

• Coolant flow switch

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22


SENSOR

J28/P28

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

J27/P27

J48/P48

ENGINESWITCHES

Engine Mounted Switches

Three EUI circuit switches are mounted on the engine:

The Low Oil Level Switch signals the ECM if the engine oil leveldecreases below a predetermined level. The ECM then warns the operatorof possible damaging conditions and logs an event.

The Filter Differential Pressure Switch signals the ECM if the pressureacross engine fuel filter is excessive and the filter needs to be changed.

The Coolant Flow Switch provides the operator with a warning if afailure in the coolant circuit causing no flow occurs. The switch contactsare normally open with no flow.

STMG 681 - 91 -1/02

82

• Coolant flow switch

• Switch functionschecked with statusscreen

24

ECM

LOW OILLEVEL

SWITCH

P1 J1

LOW OIL LEVEL

2629

COOLANT FLOWDIGITAL RETURN

F719-BR998-BR

J105 P105

12

SIGNALDIGITAL RETURN

COOLANTFLOW

SWITCH

412-BU998-BR

J47 P47

12


17 FUEL FILTER SWFUEL FILTER

DIFFERENTIALPRESSURE

SWITCH

F725-WH998-BR

J106 P106

12


EUI SWITCH CIRCUITS

The Coolant Flow Switch, like the Oil Level Switch, is a passive sensor(i.e. no power supply) which means that the ECM cannot determine if theswitch or associated circuit has failed. A system problem could bedetermined if coolant flow is indicated with the engine stopped or if nocoolant flow is indicated with the engine running.

The functions of these switches may be checked using the status screen.The Coolant Flow Switch should indicate if flow is present. This functionshould be checked both with the engine running and stopped.

83

Digital Sensors and Circuits

The following digital sensors and circuits are used on the 793C EUI fuelsystem:

- Wastegate Control Solenoid

- Exhaust Temperature Sensors

- Throttle Position Sensor

STMG 681 - 92 -1/02

• Wastegate control

• Exhaust temperature

• Throttle position

DIGITAL SENSORS AND CIRCUITS

STMG 681 - 93 -1/02

84

• Wastegate control

• Wastegate controlsolenoid currentmonitoring

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22


SENSOR

J28/P28


J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

J27/P27

J48/P48

WASTEGATECONTROLSOLENOID

The ECM controls turbocharger boost (on the 793C) with the WastegateControl Solenoid.

The ECM varies the current level to the solenoid to maintain the desiredboost pressure. This current, expressed as a percentage (0 to 100%), canbe monitored with ET on the status screen. The ET service tool alsoallows the wastegate to be manually operated for testing purposes.

Both desired and actual boost pressures can be monitored. If high boostpressure is detected, a warning is generated and the engine is derated forprotection against excessive cylinder pressure. A lower than normal boostpressure will also cause a warning to be generated.

STMG 681 - 94 -1/02

85

• ECM derates withexcessive exhausttemperature

P20/J20SPEED/TIMING

SENSOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28


J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

P31/J31

J27/P27

J48/P48

EXHAUSTTEMPERATURE

SENSORS

Two Exhaust Temperature Sensors are installed on the 793C. Thesensors are mounted between the exhaust manifold and the turbocharger.

The ECM uses the sensors to warn the operator of possibly damagingconditions and logs an event in the memory.

An engine derate occurs on Off-highway Trucks if excessive exhausttemperatures are reached.

STMG 681 - 95 -1/02

86

• Throttle positionsensor

• 8 Volt digital sensorpower supply

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35



BATTERY

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

P31/J31

J27/P27

J48/P48308-YL

113-OR


DISCONNECTSWITCH

The Throttle Position Sensor provides engine speed control for theoperator.

At engine start-up, the engine rpm is set to low idle for two seconds toallow an increase of oil pressure before the engine is accelerated.

The Throttle Position Sensor receives 8 Volts from the Digital SensorPower Supply at the ECM.

The Throttle Position Sensor is shown on the machine wiring side of thediagram.

NOTE: This system eliminates all mechanical linkages between theoperator's engine speed controls and the governor (ECM).

STMG 681 - 96 -1/02

87

• Throttle positionsensor signal

• Control defaults tolow idle with invalidsignal

• Pulse widthmodulated (PWM)signal

90%

ON

OFF

ON

OFF

ON

OFF

10%

50%

DUTYCYCLE

DUTY CYCLE = PERCENT OF TIME ON VS PERCENT OF TIME OFF

1 CYCLE

= 90%

DUTYCYCLE

= 50%

DUTYCYCLE

= 10%

PULSE WIDTH MODULATED SIGNALS

A Pulse Width Modulated (PWM) output signal is sent from the ThrottlePosition Sensor to the ECM. A PWM signal eliminates the possibility ofan erroneous throttle signal due to a short causing a possible "runaway."

If a signal problem occurs, the control defaults to the desired engine speedof low idle. If the ECM detects an out-of-normal range signal, the ECMignores the Throttle Position Sensor signal and defaults to low idle.

The sensor output is a constant frequency Pulse Width Modulated (PWM)signal to the ECM. For example, the Off-highway Truck sensor producesa duty cycle of 10 to 22% at the low idle position and 44 to 52% at thehigh idle position. The duty cycle can be read with some VOM's. Thepercent of duty cycle is translated into a throttle position of 0 to 100% bythe ECM and can be read on the ET status screen.

Other applications differ in PWM values for low and high idle. Thesevalues can be found in the Troubleshooting Guide for the appropriateapplication.

STMG 681 - 97 -1/02

88

• Throttle back-upswitch

• Throttle back-upactivated with TPSfault

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35




BATTERY

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

P31/J31

J27/P27

J48/P48308-YL

113-OR

THROTTLE BACK-UPSWITCH

DISCONNECTSWITCH

The Throttle Back-up Switch provides a "limp home" mode in the eventthat the Throttle Position Sensor becomes inoperative.

If the ECM detects either an invalid or no signal from the ThrottlePosition Sensor, the Throttle Back-up Switch is automatically activated.When activated, the operator may operate the switch to raise the enginespeed to 1200 rpm for as long as the switch is operated. If the ThrottlePosition Sensor signal is received again, the switch is deactivated.

STMG 681 - 98 -1/02

89

• Ground levelshutdown switch

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35




GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

P31/J31

J27/P27

J48/P48308-YL

113-OR

GROUNDLEVEL

SHUTDOWNSWITCH

DISCONNECTSWITCH

Engine Shutdown Systems

The Ground Level Shutdown Switch is connected to the ECM through themachine and engine wiring harnesses.

The switch signals the ECM to cut electrical power to the injectors, butmaintains power to the ECM.

This feature also enables the engine to be cranked without starting formaintenance purposes.

No other circuits may be connected to this system. The user definedshutdown feature may be used in conjunction with other circuits.

STMG 681 - 99 -1/02

90

• User definedshutdown input

• Safety feature

USER SHUTDOWN1

P2 J2


12

J3

USER SHUTDOWNDEVICE

ECM

The User Defined Shutdown feature (if installed) may be used to connectanother device to the system to shut down the engine (such as a customerinstalled fire suppression system). When the shutdown input is groundedfor one second, the engine will stop running. The input must be pulleddown below 0.5 Volts before the ECM will recognize the shutdown signal.

Operation of the User Defined Shutdown is logged as an event and canalso be shown on the ET status screen.

For example, when installed on an Off-highway Truck, this feature isprogrammed to function only during the following conditions:

Parking brake is ENGAGED

Transmission is in NEUTRAL

Machine ground speed is at ZERO

Not all machines will have this feature installed.

STMG 681 - 100 -1/02

91

• Ether injectionparameters

25294022

ECMETHER SWITCH

315-GN 317-YL

ETHER REQUESTDIGITAL RETURN

ETHER ONETHER HOLD

P1 J1

F720-GN998-BR710-BR707-WH

ETHER ON RELAY200-BK

P37 J37

ETHERSOLENOID VALVE

ETHER HOLD RELAY

315-GN

F707-WH

317-YL

K984-GY

START AIDRESISTOR

998-BR

12

+24V

ETHER INJECTION SYSTEM

Ether Injection System

The ECM controls the use of ether for cold starting. The ECM uses inputsfrom the speed/timing and coolant temperature sensors to determine theneed for ether.

The ECM cycles the ether for three seconds on and three seconds off.Actual flow is determined by engine speed and temperature. Etherinjection is disabled when the coolant temperature exceeds 10°C (50°F) orengine speed exceeds 1200 rpm.

A manual mode allows ether injection when the above parameters permit.In the manual mode, a continuous flow of ether is injected. The etherinjection status can be read on the ET status screen.

STMG 681 - 101 -1/02

92

• Two thermostatic fantypes:

- Variable speedclutch

- Hydraulic motor

• System advantages

GROUNDSTUD

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35




USER SHUTDOWN

GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY


A/C ONSWITCH

FAN SPEED SENSOR

+ BATTERY

RELAY

CYLINDER

ENGINE

ETHER START VALVE

STARTINGAID SWITCH

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

P31/J31

J27/P27

J48/P48

P84/J84

P41/J41

308-YL

113-OR

DEMAND FANCONTROL

DISCONNECTSWITCH

Demand Fan Controls

Two types of thermostatic fans are used in 3500B machine applications.Some Off-highway Trucks and Track-type Tractors are equipped with avariable speed fan drive clutch. Some Wheel Loaders are equipped with ahydraulic fan drive.

Both systems use the ECM and the temperature sensor as the enginecoolant temperature reference, and both are controlled by the ECM. If anelectrical failure of the system occurs, the fan will go to maximum (100%)speed.

The advantages of the systems are:

- Reduced fuel consumption in most conditions

- Reduced engine overcooling at low ambient temperatures

- Faster engine warm-up

- More engine power available at the flywheel

- Reduced noise

STMG 681 - 102 -1/02

93

• CAT Data Link

• Link between variousmicroprocessor basedsystems

• ET connected throughservice tool connector

• No start/nocommunicationwithout a personalitymodule file

VIMS DISPLAY MODULES

SERVICE TOOLCONNECTOR

CAT DATA LINK

VIM

SM

AIN

MO

DU

LE

ADEM IIELECTRONIC

CONTROLMODULE

(ECM)

LAPTOPCOMPUTER

CATELECTRONIC TECHNICIAN

COMMUNICATIONADAPTER

CAT Data Link

The CAT Data Link is the communication link between the ECM, EPTC II, Caterpillar Monitoring System, ET Service Tool, or PC basedsoftware and other onboard/offboard microprocessor based systems. TheCAT Data Link is a system which allows the various onboard systems tocommunicate with each other through a two wire connection. Up to 10systems can be connected on a machine.

The CAT Data Link is used for programming and troubleshooting theelectronic modules used with Caterpillar ET through the Service ToolConnector. This connector is the common access point for all onboardECM's.

It should be noted that, if a Personality Module is not installed in the ECMor is not flash programmed, the ET Service Tool will not be able tocommunicate with the ECM.

STMG 681 - 103 -1/02

94

• Data link cablestwisted to reduce RFI

• Two data linksystems:- CAT Data Link- ATA Data Link

TYPICAL CAT DATA LINK CIRCUIT

89

POWER TRAIN CONTROLMODULE

Cat Data Link +Cat Data Link -

2324

VIMS

Cat Data Link +Cat Data Link -

DEHJ

76

3132

9371

893-GN892-BRE794-YLE-793-BU

J42 P3 J3 P1 J1 ECM

Cat Data Link +Cat Data Link -ATA Data Link +ATA Data Link -

SERVICE TOOLCONNECTOR

MACHINE INTERFACECONNECTOR

The CAT Data Link is a two wire (twisted pair) electrical connection usedfor communication between electronic modules that use the CAT DataLink. The cables are twisted to reduce Radio Frequency Interference(RFI).

Typical systems connected by the data link are:

- ECM- VIMS Modules- Caterpillar ET Service Tool- Transmission Control Module

The ECM communicates with the Caterpillar Monitoring System or VitalInformation Management System (VIMS) to share engine informationsuch as engine speed, engine oil pressure, coolant temperature, filterrestriction, and electronic system faults.

Two data link systems are currently used. The CAT Data Link circuit isused for normal diagnostic and programming functions, and the ATA DataLink is used for flash programming.

STMG 681 - 104 -1/02

95

• ECM controls prelubesystem

3429

ECM

337-WH

PRELUBRICATION SYSTEM

PRELUBRICATIONDIGITAL RETURN

P1 J1

F709-BU998-BR

PRELUBRICATIONRELAY 200-BK

140-BU12

PUMPRELAY

+24V

+

MOTOR

PRELUBRICATIONMOTOR

Prelubrication System

The ECM controls the prelubrication system (if installed). This systemuses the coolant temperature, engine speed and oil pressure as itsreferences to determine the need for prelubrication.

The system is activated when the key start switch is turned to the startposition. The system prevents starter motor engagement until the oilpressure increases.

96

Logged Events

Logged events listed on the appropriate ET screen are conditions whichare abnormal to the operation of the engine. For example:

- High coolant temperature

- Low oil pressure

- Filter restriction

- Excessive engine speed

These events are not normally electronic problems, but might beconditions caused by a plugged radiator, low oil level, maintenance oroperator deficiencies.

A list of possible events for the 3500B engine is included on the nextpage.

STMG 681 - 105 -1/02

LOGGED EVENTS

• Typical logged events

• Engine events

• Event list

Some of the parameters listed in this presentation are used in the ETevents list. They are as follows:

- High coolant temperature

- High exhaust temperature

- High aftercooler temperature

- Crankcase pressure

- Loss of coolant flow

- Low (lubrication) oil pressure (according to the oil pressure map)

- User defined shutdown

- Air filter restriction

- Fuel filter restriction

- Oil filter restriction

- Engine oil level

- Engine overspeed histogram

- High boost

- Low boost

All the above parameter values can be read on the ET status screens.Events are not logged if an electronic fault is detected.

Passwords are required to clear events. This process would normally beperformed during an engine overhaul. At other times, the events shouldremain as a record of the engine history up to overhaul time.

INSTRUCTOR NOTE: To reinforce this presentation, the followingtasks can be demonstrated using a training aid or a suitable engine:

Opens and shorts in analog and digital sensors

Opens and shorts in throttle sensor

Status screens:

Read pressure and temperature readings

Switch positions

Override fan speed control

Check events log

STMG 681 - 106 -1/02

97

APPLICATION SPECIFIC SYSTEMS

This portion of the presentation discusses application specific systems inmachine applications.

The topics are:

Oil Renewal System (Off-highway Trucks)

Wastegate Control System (793C)

STMG 681 - 107 -1/02

APPLICATION SPECIFIC

SYSTEMS

• Oil renewalcomponents:

1. Oil renewal injectormanifold


98

Oil Renewal System

This system is controlled by the ECM which, depending on variousparameters, injects engine oil into the return fuel line where it mixes withthe fuel and is sent to the fuel tank.

Located on the right side of the engine are:

- Oil renewal injector manifold (1)

- Fuel pressure regulator (2)

The oil does not have to be changed when using the oil renewal system.When the oil renewal system is used, the engine oil filters, the primaryfuel filter and the secondary fuel filters must all be changed at 500 hourintervals.

STMG 681 - 108 -1/02

1

2

STMG 681 - 109 -1/02

99

• Oil flow from lubesystem to fuel tank

• Oil mixes with fuel infuel tank

FUEL TANK

PRIMARYFUEL

FILTER


(2 MICRON)

ENGINEBLOCK

OIL RENEWALINJECTOR

FUELPRESSURE

REGULATOR

FUELTRANSFER

PUMP

FUELHEATER

ECM

CYLINDERHEAD

3516B OIL RENEWAL CIRCUIT (793C)

PRIMING PUMP SUPPLY

A small amount of engine oil flows from the engine block to the oilrenewal injector manifold.

The oil flows from the oil renewal injector manifold into the return side ofthe fuel pressure regulator.

The engine oil returns to the fuel tank with the return fuel.

The engine oil mixes with the fuel in the fuel tank and flows with the fuelfrom the transfer pump to the EUI injectors to be burned with the fuel.

When the oil renewal system is used, the operator must pay close attentionto the ADD OIL message that the VIMS provides to the operator whenmakeup oil must be added.

This system, which is an attachment, includes a larger capacity oil pan. Ifthe ECM detects a low oil level, an event is logged.

For more detailed information, refer to "Oil Renewal System ServiceManual" Form RENR2223.

• Oil Renewal ServiceManual

1. Exhaust bypass valve

100

Wastegate Control

An exhaust bypass (wastegate) valve (1) prevents excessive boostpressure by diverting exhaust gasses away from the turbochargers. Thebypass valve is controlled by the ECM.

Brake system air pressure is supplied to the wastegate solenoid valve (2).If boost pressure exceeds a predetermined value, the ECM will energizethe wastegate solenoid which sends air pressure to open the exhaustbypass valve. When the exhaust bypass valve is open, exhaust gases atthe turbine side of the turbochargers are diverted to the muffler. Divertingthe turbine exhaust pressure causes the turbochargers to slow down andreduce the boost pressure to the cylinders.

For diagnostic testing, the wastegate solenoid valve can be manuallycontrolled (overridden) from minimum to maximum with the ET servicetool. The status screen can be used to read the current flowing throughthe solenoid. 0% corresponds to a closed wastegate and 100%corresponds to fully open.

The following conditions will cause the ECM to generate a derate and logan event:

20 kPa (3 psi) above desired pressure for 15 seconds causes 10% derate

30 kPa (4 psi) below desired pressure for 15 seconds causes 10% derate

STMG 681 - 110 -1/02

1

2

2. Wastegate solenoidvalve

- Controlled by ECM

• Engine wastegatesolenoid can becontrolled by ET

• Abnormal conditionsgenerate derate andevent

101

CONCLUSION

The 3500B Electronic Engine Control System is the "state of the art" inengine electronics. It combines the speed and capacity of moderncomputer systems, but at the same time is easy to service and maintain.Tasks such as re-rating the engine, which traditionally took four to eighthours, can be performed in minutes with this system.

The key to success with the 3500B EUI system is understanding thefunctions of all the components and the diagnostic tooling. This onlydevelops with practice, working with the system, operating with ET andusing all the tool functions.

INSTRUCTOR NOTE: To reinforce this presentation, the followingtasks can be demonstrated with ET:

Status screens with Oil Renewal condition status

Program Oil Renewal system

Read Wastegate current values

Compare actual with desired boost values

Manually override Wastegate Control

Check events list for abnormal Wastegate occurrences

STMG 681 - 111 -1/02

TOPRELUBRICATION

PUMP

+ BATTERY

GROUNDBOLT

15 AMPBREAKER

KEY STARTSWITCH

24 V

P20/J20SPEED/TIMING

SENSOR


CONNECTOR

COOLANTTEMPERATURE

SENSOR

8/12/16INJECTORS

GROUND BOLT

P26 T/C CONNECTOR


J2

J1

ECM


SENSOR


SENSOR

CRANKCASEPRESSURE

SENSOR

J29/P29


SENSOR

J25/P25

LOW OILLEVEL

SWITCH

ATMOSPHERICPRESSURE

SENSOR


PRESSURE SWITCH

TURBOCHARGEROUTLET

PRESSURE SENSOR

J23/P23

COOLANTFLOW

SWITCH


SENSOR

J22/P22

LEFTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR

RIGHTTURBOCHARGER

EXHAUSTTEMPERATURE

SENSOR


SENSOR

J28/P28

J35/P35





GROUNDLEVEL

SHUTDOWNSWITCH

BATTERY


A/C ONSWITCH

FAN SPEED SENSOR

+ BATTERY

RELAYCYLINDER

ENGINE

ETHER START VALVE

STARTINGAID SWITCH

J21/P21

J32/P32

J105/P105

J106/P106

J47/P47

P30/J30

J27/P27

J48/P48

P84/J84

P41/J41

308-YL

113-OR




DISCONNECTSWITCH


15 AMPBREAKER

COOLANTTEMPERATURE

SENSOR


RELAY

J21/P21

J47/P47

J103/P103

J113/P113

P31/J31

1. Title slide2. 3500B engine overview3. 3500B engine cross section4. HEUI fuel system components5. 3500B block diagrams6. 3500B major components7. 3500B engine front view8. 3500B engine rear view9. 3500B engine left side view

10. 3500B engine right side view11. Electronic control module12. EUI wiring harness13. Coolant temperature sensor14. Speed/timing sensor15. Speed/timing sensor and timing wheel16. Timing wheel17. 3500B camshaft18. Injector pushrod spring19. EUI injector20. Fuel pressure regulator21. Atmospheric pressure sensor22. Turbocharger inlet pressure sensor23. Turbocharger outlet (boost) pressure sensor24. Exhaust temperature sensor25. Lubrication oil pressure sensors26. Crankcase pressure sensor27. Timing calibration sensor28. Throttle sensor29. Fuel filters30. ECM controlled systems31. Engine component identification32. Electronic control system33. ECM34. Personality module35. Fuel injection36. Injector testing methods37. Timing control logic38. Electronic governor39. Component diagram40. Speed/timing sensor41. Speed/timing sensor and timing wheel

42. Timing wheel43. Cranking44. After pattern recognition45. Normal operation46. Timing calibration sensor47. Timing calibration48. Injection current waveform49. Fuel System Cold Modes50. Fuel system limits51. Fuel system derates52. Fuel supply system53. Fuel supply circuit54. Fuel transfer pump55. Fuel pressure regulator56. MUI and EUI Cylinder heads57. Electronic unit injector58. System power supplies list59. ECM power supply 60. ECM power supply circuit61. ECM connectors62. Speed/timing sensor power supply63. Injector wiring schematic64. Analog sensor power supply65. Digital sensor power supply66. Wastegate control solenoid power supply67. Electronic sensors and systems68. 3500B block diagrams69. Speed/timing sensor70. Analog sensor list71. Coolant temperature sensor72. Aftercooler temperature sensor73. Oil pressure sensors74. Oil pressure map75. Atmospheric pressure sensor76. Engine power derating map77 Turbocharger inlet pressure sensor78. Automatic filter compensation79. Turbocharger outlet (boost sensor)80. Crankcase pressure sensor81. Engine switches82. Coolant flow switch

SLIDE LIST

STMG 681 - 112 -1/02

83. Digital sensors and circuits list84. Wastegate control 85. Exhaust temperature sensors86. Throttle position sensor87. Pulse Width Modulated (PWM) signal88. Throttle back-up switch89. Engine shutdown systems90. User defined shutdown input91. Ether injection system92. Demand fan controls

93. CAT Data Link diagram94. CAT Data Link circuit95. Pre-lubrication system96. Logged events97. Application specific systems98. Continuous oil renewal system99. Continuous oil renewal circuit

100. Wastegate control101. 3500B block diagram

SLIDE LIST

STMG 681 - 113 -1/02

TO

PR

EL

UB

RIC

AT

ION

PU

MP

+ B

AT

TE

RYGR

OU

ND

ST

UD

15 A

MP

BR

EA

KE

R

KE

YS

WIT

CH

P20

/J20

SP

EE

D/T

IMIN

GS

EN

SO

R

J3/P

3 M

AC

HIN

EIN

TE

RF

AC

EC

ON

NE

CT

OR

CO

OL

AN

TT

EM

PE

RA

TU

RE

SE

NS

OR

GR

OU

ND

ST

UD

P26

T/C

CO

NN

EC

TO

R

J4/P

4 T

HR

OU

GH

J19/

P19

EC

M

UN

FIL

TE

RE

D O

ILP

RE

SS

UR

ES

EN

SO

R

AF

TE

RC

OO

LE

RT

EM

PE

RA

TU

RE

SE

NS

OR

CR

AN

KC

AS

EP

RE

SS

UR

ES

EN

SO

R

J29/

P29

RIG

HT

TU

RB

OC

HA

RG

ER

INL

ET

PR

ES

SU

RE

SE

NS

OR

J25/

P25

LO

W O

ILL

EV

EL

SW

ITC

H

AT

MO

SP

HE

RIC

PR

ES

SU

RE

SE

NS

OR

FU

EL

FIL

TE

RD

IFF

ER

EN

TIA

LP

RE

SS

UR

E S

WIT

CH

TU

RB

OC

HA

RG

ER

OU

TL

ET

PR

ES

SU

RE

SE

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EUI COLD MODES

COLD MODE PURPOSE TRIP SENSORTITLE POINTS

Speed Control

Elevated low idle Faster warm-up < 60°C Coolant temperature

Fuel Limiting

Cranking limit Improves starting by limiting fuel < 60°C Coolant temperature

Prevents over-fuelling during start-up

Cold Mode Cutout Cuts out dead cylinders during cold, < 60°C Coolant temperaturelow load, low speed conditions < 1300 rpm

< 25% throttle

Injection Timing

Cold Mode Timing Optimum timing for cold running < 60°C Coolant temperature

Reduces white smoke

Ether Injection

Ether injection Starting aid 10°C Coolant temperature


ECM PRESSURE CALCULATIONS

MEASUREMENT MEASURED BY RESULT

1. Atmospheric pressure atmospheric sensor = ambient press (absolute)

2. Air filter differential atmospheric - turbo inlet = filter ∆ pressure

3. Boost turbo outlet - atmospheric = boost (gauge pressure)

4. Manifold press. (A) turbo outlet sensor = boost (absolute pressure)

5. Oil pressure oil press - atmospheric = oil press (gauge pressure)

6. Oil filter differential oil press unfiltered - oil press filtered = oil filter ∆ pressure

7. Crankcase pressure (A) crankcase pressure - atmospheric = crankcase pressure (gauge pressure)

These measurements are used to provide the following:

1. Altitude and Automatic Altitude Compensation

2. Automatic Air Filter Compensation (and Restriction Indication)

3. ET Boost Measurement (gauge pressure)

4. ECM Boost Measurement (absolute pressure)

5. Operator's Dash Panel and ET Oil Pressure Indication (Lubrication)

6. Oil Filter Restriction Warning

7. High Crankcase Pressure Warning

5 Micron.0002 Inch.005 mm


2.5 Micron.0001 Inch.0025 mm


Human Hair88 Micron.0035 Inch.0889 mm

Magnified 2,000 times

How small is a Micron?

25,400 Microns = 1 Inch


SERV1681-01 Printed in U.S.A.01/02