System Description

HEI Wiring Diagram:

HEI COMPONENTS

The High Energy Ignition (HEI) distributor with Electronic Spark Timing (EST) combines all necessary ignition components in one contained unit. The system includes:
^ Integral ignition coil assembly.
^ Magnetic pick-up coil and pole piece assembly.
^ Solid state ignition module.
^ Hall effect switch.
^ RFI suppression capacitor and primary wiring harness.
^ Distributor cap and rotor.
^ Cam sensor, mounted in the distributor, for use by the PCM for control of Sequential Fuel Injection (SFI).


This system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. To provide improved engine performance, fuel economy, and control of exhaust emissions, the ECM controls distributor spark advance (timing) with the Electronic Spark Timing (EST) system.

COMPONENT DESCRIPTION

The magnetic pick-up coil assembly contains a permanent magnet, a pole piece with internal teeth, and a pick-up coil. A toothed timer core, attached to the distributor main shaft, rotates inside the pole piece. As the teeth of the timer core line up with the teeth of the pole piece, a varying current is induced in the pick-up coil. The induced current flow is converted by the HEI module into a distributor reference pulse. The HEI module, acting as the electronic ON/OFF switch, controls the current flow in the primary winding of the ignition coil. This switching action induces a high voltage in the ignition coil secondary winding which is directed through the rotor and secondary leads to fire the spark plugs.

A hall effect switch, positioned inside the distributor, serves as a cam position sensor for the sequential port fuel injection. The hall switch senses the opening point of the intake valve on the number one cylinder and provides that information to the PCM.

SPARK TIMING CONTROL

All spark timing changes in the HEI (EST) distributor are performed electronically by the Powertrain Control Module (PCM). The PCM monitors information from various engine sensors and uses this information to compute the desired spark timing and signals the distributor accordingly. A backup spark advance system is programmed in the the ignition module in case of PCM failure.