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, 400/M40REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 15 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - GASOLINE)RELAYS, SOLENOIDS, MOTORS & MODULESRELAYSFUEL PUMP RELAY
1987 Chevrolet Hi-Cube 6.2 J, 400/M40
Fuel Pump Relay
1987 Chevrolet Hi-Cube 6.2 J, 400/M40SECTION Fuel Pump Relay
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.
- If a prolonged crank is required to start vehicle, fuel pump relay may be faulty. To verify, start engine. With engine running, disconnect oil pressure switch (fuel pump back-up circuit). If engine stalls, fuel pump relay is faulty. If vehicle continues to run, relay is okay. Check for other causes of prolonged crank.
- To test fuel pump relay, disconnect fuel pump relay. Refer to COMPONENT LOCATIONS. See Fig 1. Apply battery voltage and ground to fuel pump relay winding terminals. To identify fuel pump relay terminals, see WIRING DIAGRAMS at the end of this article.
- Using an ohmmeter, check continuity between fuel pump relay power and fuel pump relay drive terminals. Continuity should exist. If continuity does not exist, fuel pump relay is defective.
- To by-pass fuel pump relay on vehicle (fuel pump not operating), turn ignition off. Disconnect fuel pump relay connector. Using a fused jumper wire, connect fuel pump test connector to positive side of battery. Fuel pump should run.
- If fuel pump runs, check for faulty connections to relay or replace defective relay. To locate fuel pump test connector, refer to COMPONENT LOCATIONS .
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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.