Spark Plug: Testing and Inspection

1. Remove the spark plug and connect to the spark plug cable.
2. Ground the spark plug outer electrode, and crank the engine.




3. Check to be sure that there is an electrical discharge between the electrodes at this time.

Inspection and Cleaning




1. 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 spark plug wrench, remove all of the spark plugs from the cylinder head.


NOTE: Take care not to allow contaminants to enter through the spark plug holes.





3. Check spark plugs for the following:
1. Broken insulator
2. Worn electrode
3. Carbon deposits
4. Damaged or broken gasket
5. 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:
Spark plug gap .............................. 1.0-1.1 mm (0.039-0.043 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 may result.
Tightening torque
Spark plug .......................... 20-30 Nm (204-306 kg.cm, 15-21 lb.ft)

Analyzing




Engine conditions can be analyzed by the tip deposits near the electrode.