GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

High Energy Ignition (HEI) Distributor


The Delco-Remy High Energy Ignition (HEI) system is a breakerless (has no ignition points), pulse triggered, transistor controlled, inductive discharge ignition system that is standard on the Buick, Olds and Pontiac vehicles covered in this guide.

There are only nine electrical connections in the system; the ignition switch feed wire and the eight spark plug leads (early models). After 1980, the EST wiring harness has to be disconnected. On most models, the coil is located in the distributor cap, connecting directly to the rotor.

The magnetic pick up assembly located inside the distributor contains a permanent magnet, a pole piece with internal teeth, and a pick up coil. When the teeth of the rotating timer core and pole piece align, an induced voltage in the pick-up coil signals the electronic module to open the coil primary circuit. As the primary current decreases, a high voltage is induced in the secondary windings of the ignition coil directing a spark through the rotor and high voltage leads to fire the spark plugs. The dwell period is automatically controlled by the electronic module and is increased with increasing engine rpm. The HEI system features, as do most electronic ignition systems, a longer spark duration which is instrumental in firing today's lean and EGR-diluted fuel/air mixtures (a lean mixture requires a much hotter, longer duration spark to ignite it than does a rich mixture). A capacitor, which looks like the condenser in the old points-type ignition systems, is located within the HEI distributor and is used for noise (static) suppression in conjunction with the vehicle's radio. The capacitor is not a regularly replaced component.

As noted in Engine Electrical , 1981 and later models continue to use the HEI distributor, although it now incorporates an Electronic Spark Timing system. With the EST system, all spark timing changes are performed electronically by the Electronic Control Module (ECM) which monitors information from various engine sensors, computes the desired spark timing and then signals the distributor to change the timing accordingly. Because all timing changes are controlled electronically, no vacuum or mechanical advance systems are used.


Engine Not Disturbed

Do not rotate the engine while the distributor is removed in order to make installing it simpler and easier. If the engine is inadvertently disturbed while the distributor is out, please refer to the appropriate procedure.

  1. Disconnect the ground cable from the battery. On 1984 and later models, disconnect the ignition switch battery feed wire and, if the vehicle is equipped with a tach, the tachometer lead from the cap.
  3. Tag and disconnect the feed and module terminal connectors from the distributor cap. DO NOT use a screwdriver to release the terminal connectors.
  5. On 1975-80 models, disconnect the hose at the vacuum advance unit.
  7. Depress and release the 4 distributor cap-to-housing retainers and lift off the cap assembly.
  9. Using a magic marker, matchmark the rotor-to-housing and housing-to-engine block positions so they can be matched during installation.

The distributor must be installed with the rotor and housing in the correct position.

  1. Loosen and remove the distributor clamp and bolt. Carefully lift the distributor just until the point where the rotor stops turning. Be careful not to disturb the position of the rotor. Now, again mark the relative positions of the rotor-to-distributor housing. The rotor must be aligned with this position before you engage distributor and camshaft drive gears during installation.

To install:
  1. With a new O-ring on the distributor housing and the rotor aligned with the second mark, install the distributor, taking care to align the mark on the housing with the one on the engine. It may be necessary to lift the distributor and turn the rotor slightly to align the gears and the oil pump driveshaft.

Make sure the distributor seats into the block fully. The base of the housing will stick up about1/4in. until the distributor gear engages the oil pump drive. Damage to the oil pump, distributor and engine may result if the distributor is forced into position by tightening the distributor clamp bolt. If the distributor will not fully seat, grab the housing and shaft, twist and wiggle until the distributor drops into the oil pump drive. If this does not work, install a socket wrench onto the large bolt on the front of the crankshaft pulley. Slowly turn the crankshaft in either direction until the distributor drops into the block fully.

  1. With the respective marks aligned, install the clamp and the bolt finger-tight.
  3. Install and secure the distributor cap.
  5. Connect the feed and module connectors to the distributor cap. Reconnect the ignition switch battery feed wire and tach connector where necessary.
  7. Connect a timing light to the engine and plug the vacuum hose, if so equipped.
  9. Connect the ground cable to the battery.
  11. Start the engine and set the timing to specifications.
  13. Turn the engine off and torque the distributor clamp bolt to 15 ft. lbs. (20 Nm). Disconnect the timing light and unplug and disconnect the hose to the vacuum advance.

Engine Disturbed

The engine MUST be completely cooled down before performing this procedure. A hot engine may cause burns and personal injury.

  1. Disconnect the negative battery cable.
  3. Remove the No. 1 cylinder spark plug. Turn the engine using a socket wrench on the large bolt on the front of the crankshaft pulley. Place a finger near the No. 1 spark plug hole and turn the crankshaft until the piston reaches Top Dead Center (TDC). As the engine approaches TDC, you will feel air being expelled by the No. 1 cylinder. If the crankshaft timing indicator says TDC has been reached but the other condition is not being met, turn the engine another full turn (360 degree). Once the engine's position is correct, replace the spark plug. Line the mark on the crankshaft damper with the 0 degree mark on the timing indicator.

When the timing marks are lined up at 0 degree, the No. 1 piston can be either on the exhaust stroke or the compression stroke. But only on the compression stroke will air be forced from the hole (on the exhaust stroke, then exhaust valve is open allowing air to escape through the manifold. Therefore, when air is felt being forced out of the spark plug hole, you can be sure the cylinder is on its compression stroke. The timing will be incorrect if the distributor is installed while aligning the rotor to fire that spark plug on the exhaust stroke.

  1. Using the firing order illustration if necessary, find No. 1 cylinder on the distributor cap. Turn the rotor until the rotor contact is approximately aligned with the wire going to No. 1 cylinder, as if the distributor had just fired No. 1 cylinder. Install the distributor as described above, turning the rotor slightly to mesh the gear teeth and oil pump driveshaft so that the rotor comes out in the proper position. Make sure the distributor is fully seated in the block before tightening the hold-down clamp.