Ignition System: Description and Operation

Ignition System Circuit.:

PURPOSE
The "Opti-Spark" ignition system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. To provide improved engine performance, fuel economy, and control of exhaust emissions. The PCM controls distributor spark advance.

OPERATION
The ignition system consists of a distributor, control circuits for ignition timing in the PCM, a separate ignition coil/Ignition Control Module (ICM) assembly, primary and secondary wiring and spark plugs.

All ignition timing is PCM controlled. There is no "by-pass" mode built into the ICM as in other ignition systems.

The distributor directs spark from the ignition coil to the proper spark plug secondary wire through a rotor. The secondary output connectors in the distributor cap are each connected to an individual spark plug. The corresponding cylinder number is molded into the distributor cap next to each output connector.

The ICM assembly provides spark to the distributor, timed by signals from the PCM. The PCM combines the camshaft position information supplied by the distributor with other system parameters and calculates the required spark advance and coil dwell. The PCM signals the ICM, which turns "ON" the primary current to the coil by grounding the primary circuit, and then turns it "OFF" by removing the ground. When primary current flow stops, high voltage is induced in the ignition coil secondary winding becomes the spark voltage for the spark plug.

LOCATION
The distributor is mounted directly to the camshaft next to the water pump. The distributor contains one signal disk and two optical Camshaft Position Sensors (CPS) that provide signals to the PCM for timing control.