Spark Plug: Testing and Inspection

SPARK PLUG SPARK TEST

NOTE: This test assumes the rest of ignition system is operating properly (meaning secondary voltage does reach the spark plugs).

1. Remove the spark plug.
2. Connect the spark plug to a high-tension lead.
3. Hold the high-tension lead and spark plug with insulated pliers 5-10 mm (0.20-0.39 in) from a ground.
4. Crank the engine and verify that there is a strong blue spark.
5. If there is no spark replace faulty spark plug.

Spark Plug Inspection:

VISUAL INSPECTION
Spark plugs
Check the following points. If a problem is found, replace the spark plug.
- Damaged insulation
- Worn electrodes
- Carbon deposits
- Damaged gasket
- Burnt

NOTE: If cleaning is necessary, use a plug cleaner or a wire brush. Also clean the upper insulator.

Visual Inspection Examples of Spark Plug Conditions:

EVALUATING SPARK PLUG CONDITION
Refer to image for examples.