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 DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEIGNITION SYSTEMIGNITION SYSTEM - HEI (CARBURETED MODELS)COMPONENT TESTINGPICK-UP COIL
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40
Pick-Up Coil
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Pick-Up Coil
NOTE:
Activation of the vacuum advance may align trigger wheel tooth and pick-up coil pole piece causing ohmmeter pointer to deflect. This deflection should not be diagnosed as a faulty pick-up coil.
- Isolate 2 pick-up coil lead wires. Remove pick-up coil connector from module. Connect ohmmeter to either terminal and ground. See Fig 1. Connect pump and apply vacuum to test vacuum advance unit. Replace vacuum advance unit if inoperative.
- Attach ohmmeter to either pick-up coil terminal and distributor housing. Select mid scale. Operate vacuum pump and observe ohmmeter throughout vacuum range. Reading should be infinite at all times. If not, replace pick-up coil. See meter "A" in Fig. Fig 1.
- Attach ohmmeter to both pick-up coil connector terminals. Operate vacuum pump and observe ohmmeter throughout the vacuum range. Replace coil if reading is not infinite at all times. See meter "A" in Fig. Fig 1.
- Connect ohmmeter to pick-up-coil terminals. Operate vacuum pump and observe ohmmeter throughout the vacuum range. Flex terminal wires by hand to check for possible intermittent defects in wiring or connectors. Replace pick-up coil if resistance is not 500-1500 ohms at all times.
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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.