1. Spark Plugs Topics covered in this presentation: Spark Plug Construction Spark Plug Reach, Seating and Heat Range Spark Plug Servicing

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 >

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 >

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

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 >

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

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 >

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

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 >

10. Spark Plugs 4 Spark plugs are made in four different thread diameters. Is this true or false? Answer True or False. Question

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 >

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 >

13. Spark Plugs Spark Plug Temperature Ideal spark plug tip temperature = 500 to 850°C. If temperature = low, carbon and combustion chamber deposits will not be burnt off. If temperature = high, the plug may overheat, damaging the electrodes. Next >

14. Spark Plugs What temperature, in degrees C, would be within the ideal range of operation? Enter your answer and press SEND. Question5

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 >

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

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 >

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 >

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 >

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 >

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

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 >

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 >

24. Spark Plugs 8 A) Carbon fouled B) Glazed deposits C) Gap bridges D) Oil fouled What is this spark plug suffering from? Question

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 >

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

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 >

28. Spark Plugs Summary You should now be aware of: Spark Plug Construction Spark Plug Reach, Seating and Heat Range Spark Plug Servicing End >