Early Models

Block Diagram:

The Electronic Ignition System consists of a distributor, Ignition Control Module (ICM), Electronic Control Unit (ECU), Crankshaft Position Sensor (CPS), engine knock sensor and an ignition relay.
The distributor is mounted at the rear of the cylinder head and is driven by a gear on the camshaft. It contains no electrical components other than the rotor and distributor cap, and its sole function is to transmit high voltage to the spark plugs in the correct firing sequence.
Proper spark advance is fully automatic, and is provided by a load table built into the ECU. When the knock sensor signals the ECU that pre-ignition is about to occur, the ECU will automatically retard ignition timing as required. When the threat of pre-ignition is eliminated as determined by engine load, the ECU will then slowly return ignition timing to its preset value.