Spark Plug: Testing and Inspection

ON-VEHICLE INSPECTION

HINT: In this section, the terms Cold and Hot refer to the temperature of the coils. Cold means approximately -10 to 50 °C (14 to 122°F). Hot means approximately 50 to 100 °C (122 to 212 °F).

INSPECT SPARK PLUG

NOTE: Do not use a wire brush for cleaning.




a. Check the electrode.
1. Using a megaohmmeter, measure the insulation resistance.

Standard resistance: 10 mohms or more

HINT:
- If the result is not as specified, clean the spark plug with a spark plug cleaner and measure the resistance again.
- If a megaohmmeter 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 properly. If the electrode is damp, proceed to the next step.




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

If there is damage, replace 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.

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




e. Clean the spark plug.

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.