Spark Plug: Testing and Inspection
ON-VEHICLE INSPECTIONNOTE: In this section, the terms "cold- and "hot- refer to the temperature of the coils. "Cold- means approximately - 10 to 50 °C (50 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.
- Do not attempt to adjust the electrode gap of a used spark plug.
a. Check the electrode.
1. Using a megohmmeter, measure the insulation resistance.
Standard insulation resistance: 10 mohms or more
HINT: If a megohmmeter 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 threads and insulator. If there is any damage, replace the spark plug.
d. Check the spark plug electrode gap.
Maximum electrode gap for a used spark plug: 1.4 mm (0.055 in.)
If the gap is greater than the maximum, replace the spark plug.
Electrode gap for a 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 of a used plug.
If the electrode has traces of wet carbon, allow it to dry and then clean with a spark plug cleaner.
Standard air pressure: 588 kPa (6 kgf/sq.cm, 85 psi)
Standard 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.