Spark Plug: Testing and Inspection

Spark Test:

CHECKING SPARK PLUGS







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 a spark plug socket, remove all 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
1. Broken insulator
2. Worn electrode
3. Carbon deposits
4. Damaged 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
Unleaded: 1.0 - 1.1mm (0.039 0.043 in.)

5. Re-insert the spark plug and tighten to the specified torque.
If it is over torqued, damage to the thread portion of cylinder head might result.

Tightening torque: 20 - 30 Nm (200 300 kg.cm, 15 21 lbft)

ANALYZING SPARK PLUGS




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

SPARK PLUG TEST (WHEN ENGINE CAN BE CRANKED)




Connect the spark plug 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.