System Description

Ignition 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 ECM controls distributor spark advance with and Electronic Spark Timing (EST) system.

Operation:

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

All ignition timing is ECM 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 ECM. The ECM combines the camshaft position information supplied by the distributor with other system parameters and calculates the required spark advance and coil dwell. The ECM 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 ECM for timing control.