Here is the stuff from duramax supplement that I got with my truck. It is pretty easy. To get the fuel filter off, either use a strap wrench or a pivoting handle filter wrench. I find it easiest to use the strap wrench.
Fuel Filter Replacement
If you want to change the fuel filter yourself, here’s how to do it:
CAUTION:
Diesel fuel is flammable. It could start a fire if something ignites it, and you could be burned.
Do not let it get on hot engine parts, and keep matches or other ignition sources away.
First, drain any water from the filter following the procedure for draining water listed previously.
Your vehicle’s engine should be off until the end of this procedure.
The fuel filter is located in the engine compartment on the passenger’s side of the vehicle, or on the driver’s side frame rail in front of the fuel tank.
1. Apply the parking brake.
2. Unplug the water sensor wire connected to the fuel filter and unscrew the filter element.
3. Remove the filter element. If there is any dirt on the filter sealing surface, clean it off. Remove and reuse the water sensor float switch located on the bottom of the fuel filter.
4. Install the new filter element.
5. Reinstall and tighten the filter container and reconnect the water sensor wire to the filter.
6. Use the fuel filter priming procedure earlier in this section to prime the fuel filter.
7. Tighten the air bleed valve by turning it clockwise until hand tight.
8. Start your engine and let it idle for five minutes. Check your fuel filter and air bleed valve for leaks.
Q: How do I prime the vehicle?
A: Your vehicle is equipped with a priming pump which is part of the engine mounted fuel filter.The priming pump is hand operated and is designed to bring fuel to the engine to eliminate any air
that may be in the fuel lines. To prime the engine, do the following:
1. You must correct the condition which caused the loss of prime by making sure there is fuel in the tank.
2. Make sure the fuel filter has been installed and properly tightened.
3. Make sure the fuel lines are properly connected and the fuel filter is cool enough to touch.
4. Remove any dirt from the fuel filter head and vent valve by wiping with a cloth.
5. Open the fuel filter vent valve by turning the screw counterclockwise several full turns. The vent valve is
located on top of the fuel filter housing.
6. Repeatedly push down on the fuel filter priming pump with the palm of your hand. The pump is located on top of the fuel filter housing. Let the pump return upward between pushes.
7. Operate the priming pump until a small amount of fuel seeps from the vent valve. When you see the fuel, the filter is now full of fuel and the system should be primed.
8. Close the vent valve. Clean any fuel which accumulated on the fuel filter. Start the engine and let idle for a few minutes. Check the filter for leaks.
To drain water, do the following:
1. Stop and park the vehicle in a safe place. Turn off the engine and apply the parking brake.
2. Remove the fuel cap.
3. Place a fuel-resistant container under the fuel filter. The filter drain valve is located in the engine, on the passenger’s side of the vehicle, on the bottom of the fuel filter.
4. Open the drain valve by turning two to three turns. When fuel empties from the valve, all the water has been drained. Close the valve hand tight. To help remove all the water, press the priming pump several times.
5. Remove the fuel-resistant container and properly dispose of the contaminated fuel. To find out how to properly dispose of contaminated diesel fuel,.
6. Install the fuel cap.
7. Start the engine and let it run for a few minutes. If the engine stalls, the fuel system may need to be primed. While draining the water from the fuel filter, air may enter the fuel system. If air has entered the fuel system the fuel system will need to be primed. If the WATER IN FUEL message comes on again after driving a short distance or the engine runs rough or stalls, a large amount of water has probably been pumped into the fuel tank. The fuel tank should be purged.
