Ignition System: Description and Operation

Ignition System Components (Typical):

Typical:

DESCRIPTION
The distributor uses a Hall Effect vane switch assembly that causes the ignition coil to be switched OFF and ON by the Powertrain Control Module (PCM). The vane switch assembly consists of a Hall Effect sensor on one side and a permanent magnet on the other side. A rotary vane cup, that is gear driven, is used to trigger the signal ON and OFF.

OPERATION
When the window of the vane cup is between the magnet and Hall Effect device, a magnetic flux field is completed from the magnet through the Hall Effect device and back to the magnet. This interruption of the primary current controls the ignition coil secondary to produce high voltage, as high as 40,000 volts, to fire the spark plugs. The signal is then used by the PCM for crankshaft position sensing and the computation of the desired spark advance based on engine demand and calibration.

The Closed Bowl distributor uses an Ignition Control Module (ICM) that is remotely mounted remotely from the distributor. The Open Bowl distributor uses an ICM that is mounted to the distributor. The distributor does not use centrifugal or vacuum advance mechanisms. A provision for fixed octane adjustment by use of a rod is also available.

DI SYSTEMS
There are two types of Distributor Ignition (DI) systems: Push start (Gray ICM) and Computer Controlled Dwell (CCD). (Black ICM)

Push Start
Push start systems feature a push start mode that allows manual transmission equipped vehicles to be push started.

Computer Controlled Dwell
The CCD system features Powertrain Control Module (PCM) controlled ignition coil charge times.

CAUTION: Do not attempt to push start an automatic transmission equipped vehicle.