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 MANUALSCHEVROLET1987HI-CUBE 6.2 J, 475/M40REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 8 (ENGINE CONTROLS - TESTS W/O CODES - GASOLINE)SYMPTOMSHARD STARTSYMPTOM DEFINITION
1987 Chevrolet Hi-Cube 6.2 J, 475/M40
Symptom Definition
1987 Chevrolet Hi-Cube 6.2 J, 475/M40SECTION Symptom Definition
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
Engine cranks okay, but does not start for a long time. Engine eventually starts and may run okay or die immediately.
Possible Causes & Corrections:
- Check for restricted exhaust system.
- Check ignition system for bare or shorted wires, incorrect pick-up coil resistance, loose ignition coil connections or moisture in distributor cap (if equipped).
- Using Spark Tester (ST-125), check for adequate spark output.
- Check ignition control circuit for short to ground.
- Remove spark plugs. Check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
- Check for shorts by misting plug wires with water.
- Check fuel pump relay. Connect test light between fuel pump test terminal and ground. Turn ignition on. Test light should illuminate for 2 seconds. If not, check fuel pump relay. See RELAYS in SYSTEM/COMPONENT TESTS - GASOLINE article in the ENGINE PERFORMANCE section. For location of fuel pump test connector, see COMPONENT LOCATIONS in appropriate SYSTEM/COMPONENT TESTS - GASOLINE article in the ENGINE PERFORMANCE section.
- Check for poor fuel quality or water-contaminated fuel.
- Check for correct fuel pressure at all speeds.
- Check for a faulty in-tank fuel pump check valve. A faulty check valve allows fuel in lines to drain back to tank after engine is stopped.
- Check EGR operation.
- Ensure ECT sensor circuit resistance or ECT sensor resistance is not too high. See SENSOR RANGE CHARTS article or DTC 15 chart in appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE section below.
- TESTS W/CODES - 4.3L
- TESTS W/CODES - 5.0L
- TESTS W/CODES - 5.7L
- TESTS W/CODES - 7.4L
- Ensure TP sensor does not stick or bind. A sticking throttle shaft or binding linkage may cause a high TP sensor voltage (open throttle indication). PCM will not control idle if high voltage is sensed. TP sensor voltage should be .85 volt with throttle closed.
- Check Idle Air Control (IAC) system. Check for foreign material in IAC bore. See DTC 35 chart in appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE section below.
- Ensure correct PROM is installed in vehicle. Check with dealer for latest application information.
- TESTS W/CODES - 4.3L
- TESTS W/CODES - 5.0L
- TESTS W/CODES - 5.7L
- TESTS W/CODES - 7.4L
RENDER: 1.0x
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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.