Ignition System: Description and Operation

Electronic Spark Control Ignition System:

PURPOSE
The ignition circuit consists of the battery, the distributor, the ignition switch, the spark plugs, and the primary and secondary wiring. This vehicle utilizes an electronic spark control system which is monitored and controlled by the Engine Control Module (ECM). All spark timing modifications in the distributor are performed electronically by the ECM. The ECM monitors information from various engine sensors, computes the desired spark timing, and signals the distributor to change the timing accordingly. No vacuum or mechanical advance mechanisms are used.

The Electronic Spark Timing (EST) system consists of an ignition module, ignition secondary, ECM, and pick up coil. The distributor has four wires that connect the ignition module to the ECM.

OPERATION
The ignition module is a switching device which can operate the primary circuit of the ignition coil, provide a square wave reference signal to the ECM, and switch circuits for the ECM to control the operation of the ignition coil primary circuit.

The ignition secondary consists of the ignition coil, rotor, distributor cap, plug wires, and spark plugs. These components supply the high voltage to fire the spark plugs.

The ECM is a microprocessor device that receives input from the ignition module, Manifold Absolute Pressure (MAP) sensor, and Coolant Temperature Sensor (CTS) and calculates an output signal to operate the ignition primary circuit.

The pick up coil is a device that generates an alternating current signal to determine crankshaft position.