Fuel System Cleaning Purge the Fuel Tank

Purge the fuel tank before being serviced.

1. Remove the fuel tank from the vehicle.

•	Refer to Fuel Tank Replacement (Suburban) for the Suburban.

•	Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Yukon/Tahoe.

•	Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.

•	Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.

•	Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.

•	Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.

•	Refer to Fuel Tank Replacement for the 4DR Utility.

2. Remove the fuel gage sender and pump unit. Refer to Fuel Pump Replacement (Main) .
3. Remove all remaining fuel from the tank.
4. Inspect the fuel tank for any remaining fuel.

1. Install tap water into the tank.

•	Move the tank to the flushing area (wash rack).

•	Agitate the water vigorously and then drain it.

2. Install a gasoline emulsifying agent into the tank. Use an available emulsifying agent, such as Product-Sol No. 913 or the equivalent.
3. Add water to the fuel tank.

•	Refer to the emulsifying agent specifications for the mixture ratio.

•	Fill the tank with water until it overflows.

•	Agitate the mixture for ten minutes.

•	Drain the tank completely.

•	Completely flush out any remaining mixture.

•	Drain the fuel tank.

•	Use an explosion meter (if available) to check for a negative reading.

•	Perform the required service work.

4. Install the fuel gage sending and pump unit. Refer to Fuel Pump Replacement (Main) .
5. Install the fuel tank into the vehicle.

•	Refer to Fuel Tank Replacement (Suburban) for the Suburban.

•	Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Yukon/Tahoe.

•	Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.

•	Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.

•	Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.

•	Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.

•	Refer to Fuel Tank Replacement for the 4DR Utility.

Fuel System Cleaning Purge Feed and Return Pipes

1. Disconnect the fuel feed and return pipes at the fuel injection unit. Refer to Fuel Hose and Pipes (Engine Fuel Pipes) for V6. Refer to Fuel Hose and Pipes for V8.

Important: 

•	Inspect the in-line fuel filter for contamination.

•	Replace the fuel filter if it is plugged.

2. Disconnect the in-line fuel filter. Refer to In-Line Fuel Filter Replacement (Except Cartridge Type) . Refer to In-Line Fuel Filter Replacement . Refer to In-Line Fuel Filter Replacement (Ex. Cart. Type 4-Door Utility) .

Important: 

•	Use only oil free compressed air to blow out the fuel pipes.

•	If the in-line fuel filter is plugged, inspect the fuel tank internally and purge if necessary.

3. Clean the fuel lines by applying air pressure in the opposite direction of fuel flow.

1. Install a new strainer (if necessary) on the fuel sender assembly. Refer to Fuel Sender Assembly Replacement .

Notice: Do not fold or twist the strainer when installing the sending unit. This action restricts fuel flow.

2. Install the fuel sender assembly with a new seal into the fuel tank.
3. Install the fuel tank.

•	Refer to Fuel Tank Replacement (Suburban) for the Suburban.

•	Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Yukon/Tahoe.

•	Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.

•	Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.

•	Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.

•	Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.

•	Refer to Fuel Tank Replacement for the 4DR Utility.

4. Disconnect the fuel feed pipe at the fuel injection unit.
5. Connect a hose to the fuel feed pipe at the fuel injection unit. Insert the other end of the hose into a 3.8 liter (one gallon) fuel can.
6. Connect the negative battery cable.
7. Add twenty-three liters (six gallons) of clean fuel into the fuel tank.
8. Purge the fuel pump and lines.
9. Using a fused jumper, connect the fuel pump test terminal to B+ to operate the fuel pump. Operate the fuel pump until 2 liters (1/2 gallon) flows into the fuel can.
10. Remove the jumper.
11. Connect the fuel line at the fuel injection unit.
12. Check for fuel leaks

12.1.

Turn the ignition ON for 2 seconds.

12.2.

Turn OFF the ignition for 10 seconds.

12.3.

Again, turn the ignition switch to the ON position.

12.4.

Check for fuel leaks.

Important: The fuel tank filler neck clamps must be properly positioned and aligned. Otherwise, the filler neck may become disconnected from the fuel tank.

Turn the ignition switch ON for two seconds then turn the switch OFF for ten seconds. Again turn the ignition switch ON and check for fuel leaks.