Spark Plug: Testing and Inspection
Procedure1. Disconnect the spark plug cable from the spark plug.
NOTE: Pull on the spark plug cable boot when removing the spark plug cable, not the cable, as it may be damaged.
2. Using a spark plug wrench, remove all of the spark plugs from the cylinder head.
CAUTION: Take care not to allow contaminants to enter through the spark plug holes.
3. Check the spark plugs for the following:
- Broken insulator
- Worn electrode
- Carbon deposits
- Damaged or broken gasket
- Condition of the porcelain insulator at the tip of the spark plug
4. Check the spark plug gap using a wire gap gauge, and adjust if necessary.
Standard value: 0.8 to 0.9 mm (0.031 to 0.034 in)
5. Re-insert the spark plug and tighten to the specified torque. If it is overtorqued, damage to the threaded portion of cylinder head might result.
Spark plug: 20 - 30 Nm (15 - 21 ft lb)
Analyzing Spark Plug
Engine conditions can be analyzed by the tip deposits near the electrode.
Spark Plug Test
If engine can be cranked, connect the spark plug to the high tension cable. Ground the outer electrode (main body), and crank the engine. In the atmosphere, only short sparks are produced because of the small discharge gap. If the spark plug is good, however, sparks will occur in the discharge gap (between the electrodes). In a defective spark plug, no sparks will occur because of a leak through the insulation.