Spark Plug: Testing and Inspection

PROCEDURE

Checking Spark Plug For Wear, Damage, Or Deposits:

- Remove spark plug wire and spark plug.

Visual Spark Plug Inspection:

- Inspect the spark plug for:

^ Improper gap
^ Carbon deposits
^ Cracked center electrode insulator

- Burned or worn electrodes (may be caused by):

^ Excessive mileage
^ Lean fuel mixture
^ Advanced ignition timing
^ Loose spark plug
^ Plug heat range too high
^ Insufficient Cooling

- Fouled plug (may be caused by):

^ Rich fuel mixture
^ Retarded ignition timing
^ Oil in combustion chamber
^ Incorrect spark plug gap
^ Plug heat range too low
^ Excessive idling/low speed running
^ Clogged air cleaner element
^ Deteriorated ignition coil, coil wire or ignition wires

- Replace the plug if the center electrode is rounded (except some platinum type plugs which have a very small diameter center electrode with an insulator that covers the electrode to the tip and may be rounded), this indicates high milage.
- Adjust the gap with a suitable gapping tool to the following specification:

0.6mm (0.024 in.)

- Reinstall spark plug. Use some anti-seize compound on the threads and torque to:

15 ft.lbs (20 Nm)

- Reconnect spark plug wire.