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 MANUALSCHEVROLET1989STEP VAN P20, 4.8 T, AUTOMATIC, 400/M40REPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMCCC TBI TESTS W/CODESDIAGNOSTIC CHARTSCHART A5 - FUEL PUMP RELAY (C, K, G, P W/SINGLE FUEL TANK)TEST DESCRIPTION
1989 Chevrolet Step Van P20, 4.8 T, Automatic, 400/M40
Test Description
1989 Chevrolet Step Van P20, 4.8 T, Automatic, 400/M40SECTION Test Description
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Fuel pump is activated if circuit No. 120 wiring is okay. If pump runs, problem may be located in fuel pump relay circuit. The following steps will locate this problem.
- Next 2 steps check for power and ground circuits to fuel pump relay.
- This determines if ECM can control the fuel pump relay.
- Oil pressure switch serves as back-up for fuel pump relay to help prevent a "NO START CONDITION". If fuel pump relay was found to be inoperative, oil pressure switch circuit should also be tested to determine why it did not operate fuel pump.
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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.