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Home › Isuzu › 1998 › Trooper LS › Repair and Diagnosis › Engine Performance › System › Engine Controls - Basic Testing › Trouble Shooting - Hombre 4.3L › Engine Cranks But Will Not Start › Fuel System

Fuel System

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See ON-BOARD DIAGNOSTIC (OBD-II) SYSTEM CHECK in TESTS W/CODES - INTRODUCTION article. After performing OBD-II 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 24). 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 (Orange wire). See 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 Gray wire 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 repair is complete, go to step 11). If connector is okay, go to next step.
  9. Replace fuel pump relay. After repair, 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 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 24).
  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 (Gray wire). See 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 (Black wire) 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 (Orange wire) to fuel pump relay harness connector terminal. After repair, go to step 24).
  15. Repair open in fuel pump relay ground circuit (Black wire). After repair, go to step 24).
  16. Check for faulty connection at VCM connector fuel pump relay control circuit (Dark Green/White wire). Check for open or short to ground in harness between fuel pump relay control connector terminal and fuel pump relay control circuit (Dark Green/White wire). Repair as necessary. After repair is complete, go to step 22). If circuits are okay, go to step 23).
  17. Check for faulty oil pressure switch connector terminals. Repair as necessary. After repair, go to step 22). If connector terminals are okay, go to next step.
  18. Replace oil pressure switch. After repair, go to step 24).
  19. Replace fuel pump. After repair, go to step 24).
  20. Repair open between fuel pump test terminal and fuel pump feed circuit (Gray wire) at fuel pump harness connector. After repair, go to step 24).
  21. Repair open in fuel pump harness ground circuit (Black wire). After repair, go to step 24).
  22. Check for open or shorted oil pressure switch connector circuits. See WIRING DIAGRAMS article. Repair affected circuit(s) as necessary. After repair(s), go to next step.
  23. Replace VCM. Program VCM. After repair, go to next step.
  24. Select CAPTURE INFO, REVIEW INFO function. If additional DTC(s) are displayed, diagnose DTC(s). See TESTS W/CODES -INTRODUCTION article. If DTC(s) are not present, system is okay.
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