Spark Plug: Testing and Inspection

Spark Plug Inspection:

1. Inspect the electrodes and ceramic insulator for:

Burned or worn electrodes may be caused by:
- Advanced ignition timing
- Loose spark plug
- Plug heat range too low
- Insufficient cooling

Fouled plug may be caused by:
- Retarded ignition timing
- Oil in combustion chamber
- Incorrect spark plug gap
- Plug heat range too high
- Excessive idling/low speed running
- Clogged air cleaner element
- Deteriorated ignition coil or ignition wires




2. Check the electrode gap.
- Adjust the gap with a suitable gapping tool.

Example Of Worn Plug:

- Replace the plug if the center electrode is rounded as shown

3. Apply a small quantity of anti-seize compound to the plug threads, and screw the plugs into the cylinder head finger-tight. Then torque them to 18 N-m (1.8 Kgf.m, 13 lb.ft).