Spark Plug: Testing and Inspection

INSPECT SPARK PLUG

NOTE:
- Do not use a wire brush for cleaning.
- Do not attempt to adjust the electrode gap of a used spark plug.




a. Check the electrode.
1. Using an mega ohmmeter, measure the insulation resistance.

Correct insulation resistance: 10 MOhm or higher

If the resistance is less than the specified value, proceed to step (d).

HINT: If the mega ohmmeter is not available, perform the following simple inspection instead.




b. Alternative inspection method:
1. Quickly accelerate the engine to 4,000 rpm 5 times.
2. Remove the spark plug.
3. Visually check the spark plug.

- If the electrode is dry, the spark plug is functioning. Reinstall the spark plug. Proceed to step 3.
- If the electrode is damp, proceed to steps (c), (d) and (e).




c. Check the spark plug for any damage on its thread and insulator.

If there is any damage, replace the spark plug. If not, reinstall the spark plug.




d. Check the spark plug electrode gap.

Maximum electrode gap for used spark plug: 1.3 mm (0.051 in.)

If the gap is greater than the maximum, replace the spark plug.

Correct electrode gap for new spark plug: 1.0 to 1.1 mm (0.039 to 0.043 in.)

NOTE: If adjusting the gap of a new spark plug, bend only the base of the ground electrode. Do not touch the tip. Never attempt to adjust the gap on a used plug.




e. Clean the spark plugs.

If the electrode has traces of wet carbon, clean the electrode with a spark plug cleaner and then dry it.

Air pressure: 588 kPa (6 kgf/sq.cm, 85 psi)
Duration: 20 seconds or less

HINT: Only use the spark plug cleaner when the electrode is free of oil. If the electrode has traces of oil, use gasoline to clean off the oil before using the spark plug cleaner.