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.
Fuel System Electrical Circuit
1999 Buick Regal LSSECTION Fuel System Electrical Circuit
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
- Ensure F/P-INJ fuse (20-amp), located in instrument panel fuse block is okay. If fuse is okay, go to next step. If fuse is faulty, go to step 20 .
- Install scan tool. Turn ignition on. Using scan tool, command fuel pump relay on. If fuel pump operates, diagnose fuel system. See BASIC FUEL SYSTEM CHECKS . If fuel pump does not operate, go to next step.
- Remove fuel pump relay. Using a fused jumper wire, jumper fuel pump relay ignition feed terminal and fuel pump feed terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 6 .
- Using a test light connected to ground, probe fuel pump relay control terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to step 7 . If test light does not illuminate, go to step 8 .
- Using a test light connected to ground, probe fuel pump relay ignition feed terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 10 .
- Using a test light connected to battery positive, probe fuel pump relay ground terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 11 . If test light does not illuminate, go to step 12 .
- Check for an open or short to ground in fuel pump relay control circuit. Repair as necessary. After repairs, go to step 25 . If circuit is okay, go to step 13 .
- Reinstall fuel pump relay. Disconnect fuel pump harness connector at fuel pump. Using a test light connected to ground, probe fuel pump harness connector feed terminal (body side). Using scan tool, command fuel pump on. If test light illuminates, go to step 14 . If test light does not illuminate, go to step 15 .
- Repair open in ignition feed circuit to fuel pump relay. After repairs, go to step 25 .
- Check for poor connection at fuel pump relay. Repair as necessary. If connection is okay, replace fuel pump relay. After repairs, go to step 25 .
- Repair open in ground circuit to fuel pump relay. After repairs, go to step 25 .
- Check connections and terminals to PCM. Repair as necessary. After repairs, go to step 25 . If connections and terminals are okay, go to step 16 .
- Using a test light connected to battery positive, probe fuel pump ground terminal (body side). If test light illuminates, go to step 17 . If test light does not illuminate, go to step 18 .
- Repair open in fuel pump feed circuit. After repairs, go to step 25 .
- Turn ignition off. Replace PCM. Perform PCM relearn procedures. After replacing PCM, go to step 25 .
- Check for an open in fuel pump feed circuit and ground circuit. Repair as necessary. After repairs, go to step 25 . If circuit is okay, go to step 19 .
- Repair open in fuel pump ground circuit. After repairs, go to step 25 .
- Replace fuel pump. After repairs, go to step 25 .
- Turn ignition off. Disconnect fuel pump harness connector at fuel pump. Remove fuel pump relay. Using a test light connected to battery positive, probe fuel pump feed terminal. If test light illuminates, go to next step. If test light does not illuminate, go to step 22 .
- Repair short to ground in fuel pump feed circuit and/or fuel injector feed circuit. After repairs, go to step 25 .
- Using a test light connected to battery positive, probe fuel pump relay ignition feed terminal. If test light illuminates, go to next step. If test light does not illuminate, go to step 24 .
- Repair short to ground in fuel pump relay ignition feed circuit. After repairs, go to step 25 .
- Check for short to ground in fuel pump feed circuit. Repair as necessary. After repairs, go to next step. If circuit is okay, go to step 19 .
- Reinstall fuel pump relay. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls, go to step 2 .
- Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.
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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.