Ignition System: Description and Operation

Ignition Circuit:

Ignition Distributor Assembly W/Integral Coil And Ignite:

This vehicle uses an electronic ignition system with computer controlled spark timing. Components include:

^ Ignition coil (integral with the distributor).
^ Camshaft driven distributor with crank angle (G1 signal) and engine speed (Ne1 signal) sensors.
^ Crankshaft pulley sensor.
^ Knock sensor.
^ Igniter (integral with the distributor).
^ Distributor cap and rotor.
^ High voltage resistor type (radio static suppressor) ignition wires.

SYSTEM OPERATION
When the key is turned "ON," current is supplied to the collector side of the igniter through the coil primary windings. The igniter contains a power transistor. The ECU signals the igniter to switch the ignition coil primary current "ON" and "OFF", firing the coil. The distributor cap and rotor distribute the sparking voltage to the correct spark plugs.

IGNITION TIMING CONTROL
Sensors in the distributor indicate crankshaft position and engine speed. A sensor on the engine (crankshaft pulley sensor) also relates crankshaft position and engine speed to the ECU. The ECU compares these signals, along with signals from other engine sensors, to determine ignition and fuel injection timing according to values stored in its memory. The knock sensor generates a small voltage spike when a knock occurs in the engine. When the ECU detects a knock, it responds by retarding the ignition timing until the knocking stops. This insures optimum spark advance under all driving conditions.

For more information on the ECU and related components, refer to COMPUTERS AND CONTROL SYSTEMS.