Ignition System: Description and Operation

Fig. 1Exploded view of High Energy Ignition (HEI) Distributor. 4-151 model shown, V6-173 similar:

Fig. 2 Electronic Spark Timing (EST) distributor. California V6-173 engines:

The High Energy Ignition (HEI) system, Fig. 1, used on these engines has an externally mounted ignition coil. On 4-151 and Federal V6-173 engines, centrifugal and vacuum advance is used to control spark timing. On V6-173 California engines, an Electronic Spark Timing (EST) distributor is used, Fig. 2, in which spark timing is controlled by the Electronic Control Module (ECM). The distributor, requires no periodic lubrications, as the lower bushing is lubricated by the engine oil and the upper bushing is lubricated by an oil filled reservoir. Dwell on HEI system is controlled by the ECM and can not be adjusted.