Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

1. Remove the negative battery cables.
2. Remove the fuel from the tank. Refer to Fuel Tank Draining .
3. Remove the fuel tank. Refer to Fuel Tank Replacement .
4. Remove the fuel sender. Refer to Fuel Sender Assembly Replacement .
5. Clean the fuel tank.

Important: The fuel tank should be replaced if the tank is rusted internally.

6. Remove the fuel strainer or replace if necessary. Refer to Fuel Sender Assembly Replacement .
7. Remove the fuel lift pump. Refer to Fuel Pump Replacement .
8. Remove the fuel manager/filter. Refer to Fuel Filter Assembly Replacement .
9. Remove the fuel return line at the injection pump.

•	Use low air pressure to blow out the lines toward the rear of the vehicle.

•	Replace the pipes if they are rusted internally.

10. Remove the fuel filter from the fuel manager housing. Refer to Fuel Filter Replacement .
11. Wipe out the inside of the housing with a clean towel.
12. Remove the heater element from the housing. Refer to Fuel Heater Replacement .
13. Remove the water in fuel sensing element from the housing. Refer to Water in Fuel Indicator Sensor Replacement .
14. Clean the inside of the filter housing with GM brake parts cleaner or equivalent.
15. Dry the housing completely.

1. Install the water- in- fuel sensing element using a new seal. Refer to Water in Fuel Indicator Sensor Replacement .
2. Install the heater element with a new O-ring seal. Refer to Fuel Heater Replacement .
3. Install the fuel filter into the fuel manager. Refer to Fuel Filter Replacement .
4. Install the fuel manager/filter. Refer to Fuel Filter Assembly Replacement .
5. Install the fuel sender. Refer to Fuel Sender Assembly Replacement .
6. Install the fuel tank. Refer to Fuel Tank Replacement .
7. Install the new fuel lift pump. Refer to Fuel Pump Replacement .
8. Install clean diesel fuel into the tank until ¼ full.
9. Install the fuel tank cap.
10. Install the negative battery cables.
11. Remove the ECM 1 fuse from the underhood relay center.

Important: Use a suitable container to catch the fuel.

12. Install a hose from the fuel injection pump inlet hose (hose to hose) at the fuel injection pump to a closed metal container with a capacity of at least 8 liters (2 gallons).
13. Crank the engine for 15 seconds with one minute cooling periods until the clean fuel is pumped out.
14. Reinstall the inlet hose to the injection pump.
15. Install the ECM 1 fuse in the underhood relay center.
16. Install a hose from the return line at the fuel injection pump to a closed metal container with a capacity of at least 8 liters (2 gallons).
17. Crank the engine for 15 seconds with one minute cooling periods until clean fuel appears at the return line.

Important: Ensure the fuel return line is in the metal container and that the container does not overflow.

•	Start the engine and allow to idle for 5 minutes.

•	Remove the hose from the metal container.

18. Reinstall the fuel return line to the injection pump.
19. Check for leaks.
20. Clear any engine DTCs.

Engine Will Run or Start

1. Drain the fuel tank. Refer to Fuel Tank Draining .
2. Fill the fuel tank to ¼ with diesel fuel.
3. Run the engine for 15 minutes.

Engine Will Not Run

1. Drain the fuel tank. Refer to Fuel Tank Draining .
2. Fill the fuel tank to ¼ with diesel fuel.
3. Remove the ECM 1 fuse from the underhood relay center.
4. Install a hose from the fuel injection pump inlet hose (hose to hose) at the fuel injection pump to a closed metal container with a capacity of at least 8 liters (2 gallons).
5. Crank the engine for 15 seconds with one minute cooling periods to purge the gasoline from the system.
6. Reinstall the inlet hose to the injection pump.
7. Install the ECM 1 fuse in the underhood relay center.
8. Start the engine.

Important: Check for leaks.

9. Run the engine for 15 minutes.
10. Clear the engine DTCs.