Ignition System: Description and Operation

PURPOSE
To produce a spark that will ignite the air/fuel mixture within an engine's cylinders, ignition systems generate high voltage and direct it to spark plugs at each cylinder. Voltage must be high enough to jump the spark plug gap under compression and it must be supplied at the correct time under a wide range of operating conditions.

DESCRIPTION
This vehicle uses an ECM controlled electronic ignition system. Components include:

1. Ignition coil.
2. Distributor with integral crank and cam angle sensors.
3. Igniter.
4. Distributor cap and high tension wiring for distributing high voltage to the spark plugs.

CRANK AND CAM ANGLE SENSORS
The crank and cam angle sensors provide the ECM with signals regarding engine rpm and #1 cylinder TDC (camshaft position). Together with other inputs, the ECM calculates ignition timing over the range of vehicle operating conditions. For additional information on these sensors, refer to COMPUTERS AND CONTROL SYSTEMS.

IGNITER
An ECM controlled igniter is used as a switch to regulate current flow through the coil primary circuit. Each time current flow is interrupted, high voltage is induced to fire the spark plugs. Except for the initial setting, timing is determined by the ECM.

SECONDARY IGNITION COMPONENTS
A distributor cap, rotor and high tension wires are used to direct high voltage from the coil to each spark plug at the appropriate time as calculated by the ECM.