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Remove distributor cap and coil assembly by removing wiring harness connector, battery lead, and cap-to-housing latches. Inspect rotor, cap, and coil assembly for arc-over. Replace parts as necessary.
To test coil primary resistance on integral ignition coil, connect ohmmeter leads to battery and "TACH" terminals on distributor cap. See Fig 1. Ohmmeter reading should be zero or nearly zero. Replace coil if not to specifications.
Connect ohmmeter leads to "TACH" terminal and ground, and note reading. Next, test coil secondary resistance by connecting ohmmeter leads to coil secondary contact (cap button) and "TACH" terminal. See Fig 1. Replace coil only if both readings are infinity.

Fig 1: Testing HEI Distributor Cap & Coil (w/ Integral Coil) Be sure leads contact proper connections.
On external coils, connect ohmmeter leads to battery and "TACH" terminals. See Fig 2. Primary resistance should read zero or nearly zero.

Fig 2: Coil Testing Connections with External Coil Touch coil mounting screw for ground.
Now connect leads to battery terminal and ground. On high scale, an infinity reading should be indicated. For secondary coil resistance, connect ohmmeter leads to "TACH" and secondary terminals. Ohmmeter should read less than infinite.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Distributor Cap & Coil Testing