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.
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HOMESERVICE MANUALSCHEVROLET1987FORWARD CONTROL 4.8 T, AUTOMATIC, 400/M40REPAIR AND DIAGNOSISENGINE PERFORMANCEIGNITION SYSTEMIGNITION SYSTEM - HEI (CARBURETED MODELS)SYSTEM TESTINGTESTING PRECAUTIONS
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40
Testing Precautions
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Testing Precautions
The following precautions MUST be observed during testing procedures:
- DO NOT ground distributor tachometer connector. Damage to ignition coil or module can result.
- Disconnect ignition switch connector at distributor before making compression checks.
- When using a timing light, attach at plug end of No. 1 spark plug wire. DO NOT pierce plug boot.
- To remove spark plug wires, twist boot 1/2 turn and pull on boot (not on wire).
- Prior to diagnosis of HEI system, visually inspect spark plug wires, plug wire boots, rotor contact button (both sides), rotor and distributor cap. If damaged or worn, replace unit(s).
- Verify wiring connector is securely attached to distributor cap. Ensure plug wires are connected at both ends before continuing test procedures.
- If engine is difficult to start or misses, check position of battery terminal connector at distributor cap. Terminal must be inserted on side of connector opposite hold-down clip. Intermittent no start condition may be caused by installation of a wrong ignition or pick-up coil.
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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.