Ignition System: Description and Operation

OPERATION

The engine controller together with the ignition coil, generates high voltage spark by opening and closing the ground path for ignition coil. Ignition timing and dwell are controlled by varying the time at which the controller opens the ground path for the coil. Battery power to the ignition coil and other control system devices is supplied through the Automatic Shutdown Relay (ASD). This ASD relay is also controlled by the engine controller. Refer to Auto Shutdown (ASD) Relay in this section for relay operation.

Base (initial) ignition timing is not set by the engine controller. Distributor position will determine base ignition timing. Electronic spark advance will be provided by the engine controller.

The amount of electronic spark advance provided by the engine controller is determined by:

^ Coolant temperature

^ Engine speed (rpm)

^ Throttle position

^ Manifold absolute pressure (MAP)

During engine cranking/start-up, the controller advances the ignition timing a set amount.

Refer to Computers and Control Systems, for further information on the engine controller and fuel injection systems.