Ignition System - HEI/Est/ESC: Diagnosis: HEI-ESC

Beware of clearance in the valve train, or a loose trailer on a hitch, as they may create sufficient vibration to be considered as detonation.

If a tip-in hesitation is occurring and a tip-in sensor is being used, be sure to check it for proper operation. It works by triggering the detonation module to provide extra advance when the engine vacuum falls below an unspecified range.

As noted earlier in the DESCRIPTION section of this article, the engine will not run without the four-connector and detonation module connected, and both modules working correctly.

For a no-start situation, the detonation module can be eliminated from the circuit by unplugging the four-wire connector at the distributor and jumping terminals "A" to "C" on the distributor side of the connection. If spark returns, the detonation module or related wiring, power, or ground is faulty.