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Home >> Isuzu >> 1996 >> Hombre XS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Trouble Shooting >> Engine Cranks But Will Not Run >> Fuel System
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Fuel System

  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. Check fuel pump relay fuse No. 9 (20-amp) located in instrument panel fuse block. If fuse is okay, go to next step. If fuse is blown, go to step 20).
  3. Install scan tool. Turn ignition on. Using scan tool, command fuel pump relay on. Fuel pump should operate for 2 seconds. If fuel pump operates as specified, see FUEL SYSTEM DIAGNOSIS. If fuel pump does not operate as specified, go to next step.
  4. Remove fuel pump relay. Connect a fused jumper wire between fuel pump feed circuit at fuel pump relay terminal No. 3 (Gray wire) and fuel pump relay ignition feed circuit at fuel pump relay terminal No. 5 (Orange wire). If fuel pump operates, go to next step. If fuel pump does not operate, go to step 6).
  5. Using a test light connected to ground, probe fuel pump relay control circuit at fuel pump relay terminal No. 2 (Dark Green/White wire). 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).
  6. Using test light connected to ground, probe fuel pump relay ignition feed circuit at fuel pump relay terminal No. 5 (Orange wire). If test light illuminates, go to step 9). If test light does not illuminate, go to step 10).
  7. Connect test light to battery voltage. Using test light, probe fuel pump ground circuit at fuel pump relay terminal No. 1 (Black/White wire). If test light illuminates, go to step 11). If test light does not illuminate, go to step 12).
  8. Check for open or short in fuel pump control circuit (Gray wire). Repair as necessary. After repairs, go to step 25). If circuit is okay, go to step 13).
  9. Reinstall fuel pump relay. Disconnect fuel pump electrical connector. Using a test light connected to ground, probe fuel pump feed circuit (Gray wire). 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).
  10. Repair open in ignition feed circuit to fuel pump relay terminal No. 5 (Orange wire). After repairs, go to step 25).
  11. Replace fuel pump relay. After repairs, go to step 25).
  12. Repair open in ground circuit to fuel pump relay terminal No. 1 (Black/White wire). After repairs, go to step 25).
  13. Check PCM connections and terminals. Repair as necessary. After repairs, go to step 25). If connections and terminals are okay, go to step 16).
  14. Using a test light connected to battery voltage, probe fuel pump ground circuit (Black wire). If test light illuminates, go to step 17). If test light does not illuminate, go to step 18).
  15. Repair open in fuel pump feed circuit (Gray wire). After repairs, go to step 25).
  16. Replace PCM. After repairs, go to step 25).
  17. Check for an open in fuel pump feed circuit (Gray wire) and ground circuit (Black wire) in wiring harness. Repair as necessary. After repairs, go to step 25). If circuits are okay, go to step 19).
  18. Repair open in fuel pump ground circuit (Black wire). After repairs, go to step 25).
  19. Replace fuel pump. After repairs, go to step 25).
  20. Turn ignition off. Disconnect fuel pump electrical connector. Remove fuel pump relay. Using a test light connected to battery voltage, probe fuel pump feed terminal (Gray wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 22).
  21. Repair short to ground in fuel pump feed circuit (Gray wire). After repairs, go to step 25).
  22. Using a test light connected to battery voltage, probe ignition feed circuit at fuel pump relay terminal No. 5 (Orange wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 24).
  23. Repair short to ground in fuel pump relay ignition feed circuit (Orange wire). After repairs, go to step 25).
  24. Check for open or short in fuel pump feed circuit (Gray wire). Repair as necessary. After repairs, go to next step. If circuit is okay, go to step 19).
  25. Check fuel pump and engine oil pressure switch and circuit. To check switch and circuit, go to next step. To by-pass this test, go to step 32).
  26. Warm engine to normal operating temperature. Ensure oil pressure is normal. Remove fuel pump relay. If engine dies, go to next step. If engine continues to run, go to step 32).
  27. Turn ignition on with engine off. Disconnect fuel pump oil pressure switch connectors. Using a test light connected to ground, probe ignition feed circuit to oil pressure switch connector terminal "C" (Orange wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 31).
  28. Reinstall fuel pump relay, leaving oil pressure switch connector disconnected. Start engine. Using a test light connected to ground, probe fuel pump feed circuit at oil pressure switch connector terminal "D" (Gray wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 30).
  29. Replace fuel pump oil pressure switch. After repairs, go to step 32).
  30. Repair open in fuel pump feed circuit (Gray wire) between fuel pump and oil pressure switch. After repairs, go to step 32).
  31. Repair open in ignition feed circuit to oil pressure switch connector terminal "C" (Orange wire). After repairs, go to step 32).
  32. Clear DTC(s) using scan tool. Attempt to start engine. If engine starts. go to next step. If engine does not start or starts and dies/stalls, go to step 2).
  33. Warm engine to normal operating temperature. Check if any DTCs are set. If any DTCs are present, diagnose DTC(s). See appropriate TESTS W/CODES article.
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