ch8_mbe4000

MBE 4000 APPLICATION AND INSTALLATION

8 FUEL SYSTEM

Section Page

8.1 FU EL SYSTE M DESC RIPTIO N .............................................................. 8-3

8.2 FU EL SYSTEM EQUIPMENT/INSTALLAT IO N G UIDELINES ................ 8-5

8.3 FU EL SELEC TION .................................................................................. 8- 10

All information subject to change without notice. 8-17SA250 0403 Copyright © 2004 DETROIT DIESEL CORPORATION

FUEL SYSTEM

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8-2 All information subject to change without notice.7SA250 0403 Copyright © 2004 DETROIT DIESEL CORPORATION


8.1 FUEL SYSTEM DESCRIPTION

The purpose of the fuel system is to keep the fuel clean and free from air or water, and to deliverthis fuel at the correct pressure to the electronic unit pump (EUP).

A fuel system consists of:

A fuel tank

Fuel prefilter

Fuel supply pump

Main fuel filter

Fuel lines

Electronic unit pump (EUP)

Engine-resident control unit (DDEC-ECU)

Injector nozzles

Check fuel valve

All necessary piping

Fuel is drawn from the fuel tank through a fuel prefilter (primary fuel filter) by the fuel pump.Fuel is then pumped through the main fuel filter (secondary filter) and through a check valve(if included) to the cylinder head. Primary and secondary filters may be combined in someapplications.

Fuel enters the EUP through the two fuel inlet filter screens located around the injector body.Filter screens are used at the fuel inlet openings to prevent relatively coarse foreign materialfrom entering the injector.

The DDEC-ECU receives data (such as temperature and speed), analyzes this data, and modulatesthe fuel system accordingly to ensure efficient engine operation. The DDEC-ECU sends a signalwhich activates the injector solenoid and determines the timing and amount of fuel delivered tothe engine.


FUEL SYSTEM

For a schematic diagram of a typical fuel system, see Figure 8-1.

Figure 8-1 MBE 4000 Fuel System Schematic Diagram



8.2 FUEL SYSTEM EQUIPMENT/INSTALLATIONGUIDELINES

The following installation guidelines cover:

Fuel Tank

Fuel Filters

Fuel Lines

Optional Devices

8.2.1 FUEL TANK

Fuel tanks must be made of the correct material, be properly designed and located, and beadequately sized regardless of the fuel tank configuration being used.

Material

Satisfactory fuel tank material is steel, aluminum, or a reinforced plastic suitable for diesel fuelapplications. The inside(s) should be clean and free from all impurities likely to contaminate thefuel.

NOTICE:

Do not use a fuel storage tank or lines or fittings made fromgalvanized steel. The fuel will react chemically with the galvanizedcoating to form powdery flakes that will quickly clog fuel filters andcause damage to the fuel pump and injectors

Fuel tanks must be properly cleaned after manufacturing so no manufacturing debris gets into thefuel.

The fuel tank(s) must not be galvanized internally under any circumstances.

The fuel tank(s) or piping may be galvanized or painted on the outside only to prevent corrosion.

Design

Baffles must be positioned to separate air from fuel and to prevent fuel from sloshing betweenthe ends of the tank(s) in mobile applications. The baffles should extend from the top to thebottom of the tank(s). These baffles should have passageways which allow the fuel to maintain aneven level throughout the tank(s).

The tank(s) should have a readily accessible drain valve at the bottom for easy removal ofcontaminants.


FUEL SYSTEM

The location of the fill neck(s) should be a clean, accessible location with sufficient height androom for an average size fill can or tanker truck hose. Position a removable wire screen ofapproximately 1.6 mm (.062 in.) mesh in the fill neck(s) to prevent large particles of foreignmaterial from entering the tank(s).

A recess on the bottom edge prevents sludge and condensation from mixing with the fuel again.A sludge drain must be provided at the lowest point.

The tank(s) must have a vent which meets applicable regulations.

A stand pipe in the tank fuel return must be utilized on MBE 4000 engines.

A properly designed fuel tank may be seen in the following illustration (see Figure 8-2).

Figure 8-2 Properly Designed Fuel Tank

Capacity

Carefully choose the capacity of the fuel tank(s) to suit the specific engine installation.Consideration should be given to length of operation without the need to refuel. The design oftanks in mobile applications must include the supply pipe so that adequate fuel is available underall operational gradients. The tank(s) capacity must be at least 5% greater than the maximum filllevel to allow for fuel expansion.

Fuel capacity of the tank(s) should be appropriate for the specific application involved.

Fuel coolers may be used.



Position

The position of the fuel tank(s) is an important factor in any application.

The position of the fuel tank(s) should ensure the following whenever possible.

The difference in height between the fuel tank(s) and engine supply pump is kept to aminimum.

The length of fuel feed pipe is kept to a minimum.

Locate the fuel tank(s) away from any excessive heat source.

The filling point is easy to access and simple to use.

The fuel pump attached to the engine has a suction height of 1.4 metres (4.5 ft). Therefore, thebottom of the fuel tank must not be more than 1.4 metres (4.5 ft) below the fuel pump (The fuelpump should not be more than 1.4 metres (4.5 ft) above the lowest fuel level possible in thefuel tank). There are some fuel systems which are over the maximum fuel restriction, 17.7 in.Hg. (600 mbar), because of the location of the fuel tank with respect to the engine regardlessof the size of the fuel lines. An electric fuel pump (not supplied by DDC) maybe needed forbigger suction heights. The fuel should be extracted at a point approximately 30 mm (1.2 in.) to50 mm (2 in.) above the bottom edge of the tank, passing through an 800 µm strainer. With araised tank (5 metres maximum), e.g. in machinery, the supply and return pipe must be providedwith a shutoff and drainage valve as close to the engine as possible. This prevents an overflow atthe filter housing during maintenance work.

The fuel tank(s) should not be located higher than the fuel pump. However, when their use isunavoidable, the fuel return line should not extend into the fuel supply so that siphoning cannotoccur in case a leak occurs in the line. The fuel return line must incorporate a check valve; thefuel inlet must incorporate a shutoff valve of the needle or globe type construction and mustnot impose any undue restriction to fuel flow.

Install a shutoff valve for use when changing the primary filter if the fuel tank(s) is above theprimary filter. This will prevent the tank(s) from draining.

A check valve in the fuel spill prevents supply side fuel from draining back into the tank(s)in a tank-below-engine installation.


FUEL SYSTEM

8.2.2 FUEL FILTER CONFIGURATION

Fuel filter requirements for the MBE 4000 engines may be found in DDC publication 7SE270.

Care should be taken not to exceed the maximum engine fuel inlet restriction17.7 in. Hg (600mBar) under any conditions, 10.29 in. Hg (350 mBar) maximum for clean filters. The fuel inletrestriction must be measured before the main filter.

Remote mounting of the filters is acceptable, given proper line sizing. Care must be taken whenremote mounting the secondary filter not to overlook the fuel temperature and pressure sensorswhere utilized. Contact DDC Application Engineering for remote filter mounting.

The fuel temperature and suction limits are DDC requirements. The fuel inlet restriction mustbe measured before the main filter.

For on-highway MBE 4000 engines there are multiple on-engine fuel filter options. These optionsinclude prefilter and main filter only, prefilter and main filter with water separator, and prefilterand main filter with water separator and heating. A hand priming pump is available with eachfilter option. A water and fuel sensor is included with on-engine water separator options.

8.2.3 FUEL LINES

The following guidelines apply to supply and return lines between the fuel filter header andthe tank(s) only.

These guidelines apply regardless of which fuel tank configuration is being used.

Do not modify or tamper with any fuel lines supplied with the engine.

The fuel inlet restriction cannot exceed 17.7 in. Hg (600 mBar) under any condition.

Design

The lines leading from the fuel tank to the engine (prefilter) must be made from scale-free steelpiping or plastic, i.e. polyamide 11, known as PA, in accordance with DIN 7728. Steel pipes mayhave to be used, depending on the ambient temperature in the engine compartment. Steel pipesmust be connected using screwed pipe connections with conical nipples in accordance with DIN3824, cap nuts in accordance with DIN 3870 and banjo bolts in accordance with DIN 7644 or7624. Hose plug connections must be used for plastic lines.

All lines should be in protected areas. These areas should be free from possible damage, andsecurely clipped in position to prevent chaffing from vibration. Take the necessary precautions toensure that the inlet line connections are tight so air cannot enter the fuel system.

The careful selection of line routing cannot be overemphasized. Avoid excessively long runs.

Minimize the number of connections, sharp bends, or other features that could lead to air trapping,excessive resistance to flow, or waxing of fuel in cold conditions.

The supply and return lines must extend to the low level of useful tank volume. Extending thereturn line to this level prevents siphoning of fuel on the supply side back to the tank.



The fuel supply line must be above the bottom of the tank to ensure that dirt and sediments are notdrawn into the fuel system. Allow 5% clearance volume above the bottom of the tank.

The supply and return lines must be well supported within the tank. Cracks on the supply sidecan cause the entrance of air and a subsequent loss of power. The supply and return lines mustbe separated by at least 12 in. inside the tank to prevent mixing of hot return fuel with cold intank fuel.

The supply line should be at the center of the tank to compensate for angular operation (seeFigure 8-2).

Material

DDC does not approve the use of copper tubing because copper becomes brittle due to coldworking when subjected to vibration. Plastic lines must be made of a reinforced plastic suitablefor diesel fuel applications.

Flexible hosing must be resistant to fuel oil, lubricating oils, mildew, and abrasion, and must bereinforced.

The lines must withstand a maximum suction of 17.7 in. Hg (600 mBar) without collapsing, apressure of 6.90 bar (100 psi) without bursting, and temperatures between -40 C (-40 F ) and149 C (300 F).

Size

The fuel supply lines must be 10 mm ID or larger. The return lines must be 10 mm ID or larger.The minimum nominal diameter must be 12 mm ID (0.5 in.) if the pipe lengths exceeds 6 m.The restrictions imposed between the tank and fuel supply pump inlet determine the requiredfuel supply line diameter.

The determinant of fuel line size is the restriction measured at the inlet of the engine. Themaximum allowable inlet restriction is 17.7 in. Hg (600 mBar) for all applications.

8.2.4 OPTIONAL DEVICES

The optional devices for the fuel system that may be used are a fuel cooler and a fuel waterseparator.

Fuel Cooler

If the engine fuel inlet temperature exceeds 80 C (176 F) under anticipated operating conditions,a fuel cooler is required.

Fuel Water Separator

A fuel water separator is required. The total fuel inlet system may not exceed the maximumrestriction of 10.29 in. Hg (350 mBar).


FUEL SYSTEM

8.3 FUEL SELECTION

The quality of fuel used is a very important factor in obtaining satisfactory engine performance,long engine life, and acceptable exhaust emission levels. For information on fuel selection, referto DDC publication 7SE270, “Lubricating Oil, Fuel and Filters.”


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