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Home >> GMC >> 1997 >> Forward Control 4.3 W, L35, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 8 (Engine Controls - Basic Engine Testing - 7.4L (P Series)) >> No-Start Diagnosis >> No Start - Engine Cranks Okay >> Fuel System

Fuel System

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  1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
  2. Turn ignition off for about 10 seconds. Turn ignition on. Fuel pump should operate for about 2 seconds. If fuel pump operates as specified, go to IGNITION SYSTEM check. If fuel pump does not operate as specified, go to next step.
  3. Connect a fused jumper wire between battery positive and fuel pump test terminal. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 12).
  4. Disconnect jumper wire from test terminal. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should operate for about 2 seconds. If fuel pump operates as specified, go to step 25). If fuel pump does not operate as specified, go to next step.
  5. Remove fuel pump relay. Turn ignition on with engine off. Using a test light connected to ground, probe fuel pump relay harness connector battery feed terminal (Orange wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
  6. Connect test light between ground and fuel pump relay harness connector battery feed circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 15).
  7. Connect test light between ground and fuel pump relay terminal. Turn ignition off for 10 seconds. Turn ignition on. If test light illuminates for 2 seconds, then turns off, go to next step. If test light does not illuminate, go to step 16).
  8. Check for faulty fuel pump relay harness connector. Repair as necessary. After repairs, go to step 11). If connector is okay, go to next step.
  9. Replace fuel pump relay. After repairs, go to next step.
  10. Start and warm engine to normal operating temperature. Ensure oil pressure is within normal range. Disconnect fuel pump relay. If engine continues to run, go to next step. If engine stalls/dies, go to step 17).
  11. Reinstall fuel pump relay. Turn ignition off. Using a test light connected to ground, probe fuel pump test connector. If test light illuminates, go to step 18). If test light does not illuminate, go to step 25).
  12. Disconnect fuel pump harness connector. Using a fused jumper wire connected to battery voltage, jumper fuel pump test terminal. Using a test light connected to ground, probe fuel pump feed circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 20).
  13. Connect test light to fuel pump ground terminal on harness connector. If test light illuminates, go to step 19). If test light does not illuminate, go to step 21).
  14. Repair open in battery feed circuit to fuel pump relay harness connector terminal. After repairs, go to step 25).
  15. Repair open in fuel pump relay ground circuit. After repairs, go to step 25).
  16. Check for faulty connection at VCM connector fuel pump relay control circuit. Check for open or short to ground in harness between fuel pump relay control connector terminal and fuel pump relay control circuit. Repair as necessary. After repairs, go to step 22). If circuits are okay, go to step 24).
  17. Check for faulty oil pressure switch connector terminals. Repair as necessary. After repairs, go to step 22). If connector terminals are okay, go to next step.
  18. Replace oil pressure switch. After repairs, go to step 25).
  19. Replace fuel pump. After repairs, go to step 25).
  20. Repair open between fuel pump test terminal and fuel pump feed circuit at fuel pump harness connector. After repairs, go to step 25).
  21. Repair open in fuel pump harness ground circuit. After repairs, go to step 25).
  22. Repair affected circuit as necessary. After repairs, go to step 25).
  23. Repair connectors as necessary. After repairs, go to step 25).
  24. Replace VCM. Perform VCM relearn procedures. After repairs, go to next step.
  25. Clear DTC(s) using scan tool. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls/dies, go to step 2).
  26. Warm engine to normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTC(s) are present, diagnose DTC. See the TESTS W/CODES article. If DTC(s) are not present, go to next step.
  27. Select CAPTURE INFO, REVIEW INFO function. If additional DTC(s) are displayed, diagnose DTC(s). See the TESTS W/CODES article. If DTC(s) are not present, system is okay.
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