Ignition System: Description and Operation

PURPOSE
The ignition system provides spark control during all modes of engine operation.

OPERATION
The system consists of 3 sub-systems; primary ignition, secondary ignition, and timing control.

When ignition is switched "ON," it charges the primary coil windings. When the engine is running, the ignition control module induces a spark by grounding the coil primary circuit negative side.

When the ignition module grounds the primary circuit, inductive charge built up in the secondary circuit sends spark from the coil to the distributor. The rotor and cap then sends spark to each plug.

The ignition timing is modified by the Powertrain Control Module (PCM). Based on inputs from the Barometric Pressure (BARO) sensor, at altitudes of 1000m (3,280 ft) or higher, the PCM will signal the ignition module to advance ignition timing. The distributor also uses governor weights and a dual vacuum advance diaphragm to advance the timing.

CONSTRUCTION
The engine uses an integrated distributor mounted system with vacuum advance.

Primary Ignition
The primary ignition components include coil primary circuit, ignition control module, and ignition switch.

Secondary Ignition
The secondary ignition components include spark plugs and wires, distributor cap, rotor, and coil secondary circuit.