Spark Plugs Topics covered in this presentation: Spark Plug
Construction Spark Plug Reach, Seating and Heat Range Spark Plug
Servicing Slide 2 Spark Plugs The Spark Plug The spark plug:
Typical spark plug components: Ribbed insulator Terminal Insulator
nose Centre electrode Ground electrode Shell Conductive seal
Ignites the air and fuel mixture. Removes heat from the combustion
chamber. Next > Slide 3 Spark Plugs The Steel Shell The shell is
threaded so it can be screwed into the cylinder head. To minimize
corrosion, its surface is electroplated with nickel. Thread It is
machined with a hexagonal section, for plug removal and fitting.
Hex Next > Slide 4 Spark Plugs How many sides does a spark plug
have on the part designed for plug removal and replacement? Enter
your answer and press SEND. Question1 Slide 5 Spark Plugs Purpose:
The Ceramic Insulator It is made from aluminium oxide and glazed to
discourage dirt. Ribs increase the surface area of the insulator to
reduce flashover to ground. Nose Ribs To prevent high voltages from
shorting to ground. To remove heat from the combustion chamber.
Next > Slide 6 Spark Plugs 2 A) Aluminium nitrate B) Aluminium
hydroxide C) Aluminium oxide D) Aluminium carbonate What material
is the spark plug's ceramic insulator made from? Question Slide 7
Spark Plugs Electrodes are made from nickel alloy or platinum.
Ground and Centre Electrodes The ground electrode is welded to the
shell. They must be resistant to high temperatures and corrosion.
The centre electrode has a machined tip. Ground electrode Centre
electrode Spark erosion Next > Slide 8 Spark Plugs 3 A) Shell B)
Ceramic insulator C) Centre electrode D) Insulator nose In a spark
plug, what is the ground electrode connected to? Question Slide 9
Spark Plugs Spark Plug Dimensions Thread Diameter Spark gap Thread
diameter Reach Spark Gap Spark Plugs are made in 10, 12, 14, and 18
mm thread diameters. The gap must be correct. If it is too small, a
weak spark is produced. If it is too large, the mixture will burn
inefficiently. Next > Slide 10 Spark Plugs 4 Spark plugs are
made in four different thread diameters. Is this true or false?
Answer True or False. Question Slide 11 Spark Plugs Spark Plug
Dimensions Correct reach Cylinder head Too short Too long Spark
Plug Reach Incorrect reach can cause engine running problems or
spark plug damage. Next > Slide 12 Spark Plugs Spark Plug
Seating Flat SeatingSpark plugs must be fitted with a metal washer
to seal combustion chamber and remove heat. Metal washer No washer
Conical SeatingNo washer required as plug is sealed by its conical
seat. Next > Slide 13 Spark Plugs Spark Plug Temperature Ideal
spark plug tip temperature = 500 to 850C. If temperature = low,
carbon and combustion chamber deposits will not be burnt off. If
temperature = high, the plug may overheat, damaging the electrodes.
Next > Slide 14 Spark Plugs What temperature, in degrees C,
would be within the ideal range of operation? Enter your answer and
press SEND. Question5 Slide 15 Spark Plugs 100% Fresh air Heat
Dissipation The combustion process produces heat. 20% is absorbed
by intake stroke fresh air. Dissipation occurs as follows: 58% is
absorbed by the cylinder head walls. 20% is absorbed by the
insulator and spark plug side walls. 2% is absorbed by spark plug
wires. 2% 10% 58% 20% Next > Slide 16 Spark Plugs 6 A) 2% B) 20%
C) 25% D) 58% Approximately what percentage of heat from the
combustion process is absorbed by the cylinder head walls? Question
Slide 17 Spark Plugs Spark Plug Heat Range Heat range = spark
plug's ability to remove combustion chamber heat. Determined by:
Insulator nose length = distance from tip of insulator to where it
meets the metal shell. Insulator nose length Insulator nose length.
Gas volume around the insulator nose. Composition of the insulator
and the centre electrode. Next > Slide 18 Spark Plugs Spark Plug
Heat Range Hot Plug: Long insulator nose, exposing a large surface
area to combustion gases. Cold Plug: Shorter insulator nose,
minimizing surface area exposed to combustion gases. Dissipates
heat slowly. Firing end heats up quickly. Dissipates heat quickly.
Firing end heats up slower. Next > Slide 19 Spark Plugs Other
Types of Spark Plugs Some spark plugs have multiple ground
electrodes. They provide multiple spark paths which reduces spark
erosion. This surface discharge plug can be used with CDI systems.
It provides good sparking, even when fouled. Next > Slide 20
Spark Plugs Resistor Spark Plugs Spark plug with carbon compound
resistor in centre core. The resistor suppresses radio frequency
interference (RFI). Plug with carbon resistor Resistance material
Next > Slide 21 Spark Plugs 7 A) Ferrite beads B) Wire wound
resistor C) Capacitor D) Carbon resistor What can be incorporated
into a spark plug to suppress radio frequency interference?
Question Slide 22 Spark Plugs Spark Plug Removal Typical Procedure:
Use an air line/brush to remove all debris from around each plug.
Remove all plugs and place on bench in cylinder order. Inspect each
spark plug. Remove the lead from each plug, by using the rubber
boot. Slacken each spark plug. Next > Slide 23 Spark Plugs Spark
Plug Conditions Normal use Overheated Gap bridged Cracked
insulation Pre-ignition Carbon fouled Deposit fouled Splashed
deposits Oil fouled Glazed deposits Next > Slide 24 Spark Plugs
8 A) Carbon fouled B) Glazed deposits C) Gap bridges D) Oil fouled
What is this spark plug suffering from? Question Slide 25 Spark
Plugs Tool to alter gap Feeler gauge Spark Plug Gap Adjustment
Obtain gap information from shop manual. If necessary, adjust gap
using feeler gauge tool. It should be a sliding fit. Typical
Procedure: Check gap between electrodes with a feeler gauge. Next
> Slide 26 Spark Plugs 9 A) Micrometer B) Ruler C) Feeler gauge
D) Microscope What device is normally used to measure the spark
plug gap? Question Slide 27 Spark Plugs Conical seat Flat seat
Spark Plug Fitting Apply grease to spark plug threads. Tighten
plugs as per shop manual. Refit spark plug leads. Typical
Procedure: Hand screw spark plugs into cylinder head. 90 15 Next
> Slide 28 Spark Plugs Summary You should now be aware of: Spark
Plug Construction Spark Plug Reach, Seating and Heat Range Spark
Plug Servicing End >
