Spark Plug: Testing and Inspection

Spark Plug Inspection:

1. Inspect the spark plugs for:
- Improper gap
- Carbon deposits
- Cracked center electrode insulator
- Burned or worn electrodes (may be caused by):
- Excessive mileage
- Lean fuel mixture
- Advanced ignition timing
- Loose spark plug
- Plug heat range too high
- Insufficient Cooling
- Fouled plug (may be caused by):
- Rich fuel mixture
- Retarded ignition timing
- Oil in combustion chamber
- Incorrect spark plug gap
- Plug heat range too low
- Excessive idling/low speed running
- Clogged air cleaner element
- Deteriorated ignition coil, coil wire or ignition wires

2. Replace the plug if the center electrode is rounded.

Gapping Spark Plug:

3. Adjust the gap with a suitable gapping tool.

Electrode Gap: 0.031 - 0.035 in. (0.8 - 0.9 mm).