Ignition System: Description and Operation

System Schematic Diagram:

The Electronic Ignition System consists of a distributor, Ignition Control Module (ICM), Electronic Control Unit (ECU), Crankshaft Position Sensor (CPS), sync pulse generator, and engine knock sensor. Proper spark advance is fully automatic, and is provided by a load table built into the ECU. The Electronic Control Unit (ECU) controls the entire ignition system. It monitors engine operating conditions with the: Manifold Absolute Pressure (MAP) sensor, Coolant Temperature Sensor (CTS), Manifold Air Temperature (MAT) Sensor, Crankshaft Position Sensor (CPS), and the knock sensor. Based on this information the ECU provides the Ignition Control Module (ICM) with the correct ignition timing for any operating condition. 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. Crankshaft position information is also used to trigger the fuel injection system.