Spark Plug: Testing and Inspection

INSPECTION AND REPAIR





The spark plug affects entire engine performance and therefore its inspection is very important.
- Check electrode and insulator for presence of cracks, and replace if any.
- Check electrode for wear, and replace if necessary.
- Check gasket for damage, and replace if necessary.
- Measure insulation resistance with an ohmmeter, and replace if faulty.
- Adjust spark plug gap to 0.8 mm - 0.9 mm (0.0315 in - 0.0354 in).

NOTE:
- Do not damage to tip of spark plugs.
- Do not cleaning the spark plugs. If require the cleaning it due to heavy dirt, it is allowed only 20 seconds to be used spark plug cleaner.

- Check fuel and electrical systems if spark plug is extremely dirty.

Sooty Spark Plugs
Much deposit of carbon or oil on the electrode and insulator of spark plug reduces the engine performance.

Possible causes:
- Too rich mixture
- Presence of oil in combustion chamber
- Incorrectly adjusted spark plug gap

Burning Electrodes
This fault is characterized by scorched or heavily oxidized electrode or blistered insulator nose.

Possible causes:
- Too lean mixture
- Improper heat value

Measuring Insulation Resistance
- Measure insulation resistance using a 500 volt megaohm meter.




- Replace spark plugs if measured value is out of standard.
Insulation resistance: 50 M Ohms or more