Engine Ignition

The electronic ignition (EI) system for the 3.9L and the 4.2L engines consists of the following components:

• Crankshaft position (CKP) sensor
• Ignition coil
• Spark plugs
• Spark plug wires

The crankshaft position (CKP) sensor:

• is a variable reluctance sensor.
• is mounted on the engine front cover.
• is triggered by a 36-minus-1 tooth trigger wheel located on the crankshaft pulley and damper.
• provides base timing and crankshaft speed (rpm) to the powertrain control module (PCM).

For more information, refer to ELECTRONIC ENGINE CONTROLS article.

The ignition coil:

• is controlled by the powertrain control module.
• fires 2 spark plugs simultaneously.

The spark plugs:

• ignite the fuel and air mixture.
• are platinum enhanced for long life.

The spark plug wires:

• carry high voltage pulses from the ignition coil to the spark plugs.