Spark Plug: Testing and Inspection

SPARK PLUG TEST

1. Remove the spark plug and connect to the spark plug cable.
2. Ground the spark plug outer electrode (body), and crank the engine.
- Check to be sure that there is an electrical discharge between the electrodes at this time.

INSPECTION OF SPARK PLUGS

1. Disconnect spark plug cable from the spark plug. If the spark plug cable is removed by pulling on the cable, it may be damaged.

2. Using a plug wrench, remove all plugs from cylinder head.

CAUTION: Use care not to allow foreign matter to enter through plug holes.

3. Check the spark plugs for the following:
Broken insulator
Worn electrode
Carbon deposits
Damaged or broken gasket
Burnt condition of porcelain insulator at spark gap.

NOTE: Dark deposits indicate too rich a fuel mixture, light (white) deposits indicate too lean a fuel mixture, advanced ignition timing or insufficient plug tightening

4. Check plug gap using a plug gap gauge and adjust if necessary.
Standard value: .040 - .043in (1.0 - 1.1mm)

5. Tighten spark plug to specified torque. If overtorqueing occurs, damage to threaded portion of cylinder head might result.
Spark plug torque: 15-21 ft lb (20 - 30Nm)