Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
HEI/Est Ignition System
Spark
Check for spark at coil wire and at each spark plug wire using a high output spark tester. Check spark plug wire resistance on suspect wires. Resistance should less than 30,000 per wire.
Ignition Coil Power Source
Turn ignition on. Using voltmeter, check voltage between terminal B+ (Red/White wire) and ignition coil ground. Battery voltage should be present.
Ignition Coil Testing
1) Using an ohmmeter, check continuity between B+ terminal and base of ignition coil. See Fig 1 . Reading should be high (infinite or open circuit). If reading is not infinite or open, replace coil.
2) Check continuity between "B+" terminal and "C-" terminal. Reading should be low or zero (continuity). If not, replace coil.
3) Check continuity between "C+" terminal and coil secondary terminal. If reading is infinite (open circuit), replace coil.
Distributor & Ignition System Check
Use circuit wiring diagram and diagnostic flow chart (C-4B) to diagnose and service ignition system. See Fig 2 and Fig 3 .
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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