GM Service Manual Online
For 1990-2009 cars only

This procedure checks for the presence of water and gasoline in diesel fuel that may cause injection pump and nozzle damage.

Remove the fuel filter element and inspect it.

    • If water, gasoline or fungi/bacteria are not present, end the inspection.
    • If water or fungi/bacteria are present, Go to Cleaning Water from the Fuel System.
    • If gasoline is present, Go to Cleaning Gasoline from the Fuel System.

Cleaning Water from the Fuel System

  1. Disconnect the batteries.
  2. Drain the fuel tank.
  3. Remove the fuel tank (Refer to Fuel Tank Replacement).
  4. Remove the fuel sender unit (Refer to Fuel Sender Assembly Replacement ).
  5. Inspect the fuel tank and the fuel sender for rust, fungi or bacteria.
  6. Clean the inside of the fuel tank and the fuel sender with hot water.
  7. Use compressed air in order to dry the fuel tank and the fuel sender.
  8. Disconnect the ends of the following lines:
  9. • The lift pump suction line
    • The lift pump feed line
    • The fuel filter outlet line
    • The fuel filter drain line
    • The fuel return line
  10. Inspect each of the pipes.
  11. Replace any rusted pipes.
  12. Clean the inside of the fuel filter housing.
  13. Dry the fuel filter housing with compressed air.
  14. Dry the inside of each line with low pressure air.
  15. Remove the FUEL SOL fuse from the fuse panel.
  16. Install a new fuel filter element.
  17. Install the fuel sender and the fuel tank (add clean diesel fuel to ¼ full).
  18. Reconnect the following lines:
  19. • The lift pump suction (both ends) lines.
    • The lift pump feed (both ends) lines.
    • The fuel filter drain line.
    • The fuel return (at the injection pump) line.
  20. Connect the fuel filter outlet and the fuel return line at the fuel sender to the hoses that flow to the metal containers.
  21. Connect the batteries.
  22. Use the scan tool in order to command the lift pump ON.
  23. Operate the lift pump until clean fuel flows from the fuel filter outlet into a metal container.
  24. Connect the hose from the fuel filter outlet to the injection pump inlet.
  25. Open each injection line at its nozzle end and crank the engine until clean fuel flows from it.
  26. • Use two wrenches when loosening the injection line fittings.
    • Allow a maximum of 15 seconds cranking time, followed by 1 minute of cranking motor cooling time.
  27. Tighten each injection line fitting at its nozzle. Use two wrenches when tightening the injection line fittings.
  28. Install the FUEL SOL fuse in the fuse panel.
  29. Start and run the engine for 1 minute while the fuel flows from the fuel return line into a metal container.
  30. Stop the engine.
  31. Connect the fuel return hose to the fuel sender.
  32. Clean any fuel spillage from the engine.
  33. Fill the fuel tank and add a biocide, if needed.

Cleaning Gasoline from the Fuel System

  1. Drain the fuel tank.
  2. Fill the fuel tank.
  3. Remove the FUEL SOL fuse from the fuse panel.
  4. Remove the fuel filter outlet and connect it to a hose that flows to a metal container.
  5. Use a scan tool and command the lift pump ON until clean fuel flows from the fuel filter outlet into a metal container.
  6. Connect the hose from the fuel filter outlet to the injection pump inlet.
  7. Install the FUEL SOL fuse into the fuse panel.
  8. Attempt to start and run the engine for 15 minutes (If engine does not start, purge the injection system).
  9. Stop the engine.
  10. Clean any fuel spillage from the engine.
  11. Clear the engine of any DTCs.