Chevrolet Chevette/1000 1976-1988 Repair Guide

Description and Operation



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Fig. Fig. 1View of the High Energy Ignition (HEI) system

All gasoline engine Chevette and Pontiac 1000 models are equipped with High Energy Ignition (HEI). This is a pulse triggered, transistor-controlled, inductive discharge ignition system that uses no breaker points. The HEI distributor contains a pick-up assembly and an electronic module which perform the function of breaker points. Centrifugal and vacuum advance mechanisms are basically the same as those in breaker point distributors. 1981-88 models are equipped with EST (Electronic Spark Timing) distributors which have no mechanical or vacuum advance mechanisms. The ignition coil is mounted externally, on the left side of the engine, beneath the intake manifold, and is not visible on air conditioning equipped cars. The coil has a plastic cover.

The voltage delivered by this system is also far greater than the conventional system, enabling longer spark plug life as the hotter plug won't be as susceptible to fouling. There is no regular servicing of the distributor other than checking the distributor cap and rotor for burning and pitting.


Before going on to troubleshooting, it might be a good idea to take note of the following precautions:

Timing Light Use

Inductive pick-up timing lights are the best kind of use with HEI. Timing light which connect between the spark plug and the spark plug wire occasionally (not always) give false readings.

Spark Plug Wires

The plug wires used with HEI systems are of a different construction than conventional wires. When replacing them, make sure you get the correct wires, since conventional wires won't carry the voltage. Also, handle them carefully to avoid cracking or splitting them and never pierce them.

Tachometer Use

Not all tachometers will operate or indicate correctly when used on a HEI system. While some tachometers may give a reading, this does not necessarily mean the reading is correct. In addition, some tachometers hook up differently from others. If you can't figure out whether or not your tachometer will work on your car, check with the tachometer manufacturer. Dwell readings, or course, have no significance at all.

HEI System Testers

Instruments designed specifically for testing HEI systems are available from several tool manufacturers. Some of these will even test the module itself. However, the tests given in the following section will require only ohmmeter and a voltmeter.