Changing The Fuel Filter In An Lbz: Step-By-Step Guide

Changing the fuel filter on a Chevy/GMC Duramax LBZ is a relatively simple task that can be done at home. The process involves removing the passenger-side inner fender, unplugging the water sensor, unscrewing the old filter, installing a new one, and reconnecting everything. Some tools that may be needed include a filter wrench, channel locks, and a clip tool for removing the fender clips. It is also recommended to have a plastic bag on hand to catch any spilled fuel and to grease the O-rings with petroleum-based grease. The fuel filter should be changed regularly, with some sources recommending intervals of 5000, 9000, 10000, or 15000 miles, or when the Change Fuel Filter indicator comes on.

Disconnect the WIF sensor and other plugs

Disconnecting the WIF sensor and other plugs is a crucial step in changing the fuel filter on an LBZ engine. Here is a detailed guide on how to perform this task effectively:

Firstly, locate the WIF sensor and the accompanying plugs. They are usually found near the fuel filter housing. Before disconnecting anything, place a plastic bag or a container underneath the WIF sensor to catch any spilling fuel. You don't want to spill diesel fuel on the engine components or the frame, as it can cause damage over time.

Once you have safely positioned the container, proceed to carefully disconnect the WIF sensor and the associated wiring plugs. Gently pull the plugs apart, taking care not to damage the connectors. Set the disconnected plugs aside, ensuring they are away from the work area to avoid any accidental reconnection.

With the WIF sensor and plugs disconnected, you can now focus on removing the fuel filter. Loosen the fuel filter by hand or use a strap-style filter wrench if needed. Turn the fuel filter counterclockwise to unscrew it. Have a container ready to catch the fuel that will drain from the filter. Once the filter is removed, clean the area with water to remove any spilled fuel residue.

Now, you can focus on the WIF sensor itself. Using a large pair of channel locks or a suitable wrench, carefully unscrew the WIF sensor. You can place the fuel filter in a vise to secure it and make this process easier if desired. Once the WIF sensor is removed, take the opportunity to inspect the O-rings for any damage or wear. Replace the O-rings if necessary.

This step is crucial for ensuring a proper seal when installing the new fuel filter. Apply a suitable lubricant, such as diesel fuel, motor oil, or petroleum grease, to the new O-rings. This will help ensure a tight seal and prevent leaks. Now, you are ready to install the new fuel filter. Hand-tighten the new fuel filter, ensuring it is securely in place.

Finally, reconnect the WIF sensor wiring and any other disconnected plugs. Ensure all connections are secure and correctly attached. Start the engine and check for any leaks around the fuel filter and WIF sensor. If no leaks are detected, you have successfully changed the fuel filter and disconnected/reconnected the WIF sensor and plugs.

Remove the filter and housing

To remove the filter and housing, you will need a 12mm wrench, a pair of pliers, about 10" of 1/2" hose (you should have enough left over from the AD system), and two hose clamps.

First, disconnect the WIF sensor and the other plug that is connected to it. Remove the two clamps (a little bit of diesel will come out, so be careful not to press the primer on the stock housing). Using the 12mm wrench, remove the two bolts. Now, you can remove the whole filter and housing. Take the hose clamps and hose and place them back on the hard fuel lines.

Alternatively, you can remove the passenger-side battery and remove and replace the filter and housing from the top. You can also remove the passenger fender well skirt and remove and replace the filter and housing from the bottom.

Use a filter wrench to unscrew the old filter

To change the fuel filter on your LBZ, you'll need a filter wrench. This will help you to unscrew the old filter and screw on the new one.

First, you'll need to remove the wire from below the old filter. Then, with your filter wrench, start to unscrew the old filter. You might be able to do this by hand, so try this first. If you can't get a good grip, the filter wrench will help you get enough leverage to start unscrewing. Be careful not to spill diesel everywhere as you remove the old filter. You might want to put a plastic bag around the filter to catch any spills.

Once you've removed the old filter, you'll need to empty and clean the filter housing. Make sure you also check the gasket in the middle of the filter head and remove it if it's still attached to the filter head. You don't want two gaskets in place when you add the new filter, as this will make it impossible to get a tight fit.

Now you can add the new filter. Some people recommend greasing the O-rings with petroleum jelly or diesel, but this is not essential. Screw the new filter into place by hand. You don't need to over-tighten it, just make sure it's secure.

Now you can reconnect the wire to the Water in Fuel (WIF) sensor and you're done!

Fill the new filter with diesel before installing

Filling the new filter with diesel before installing it is a crucial step in changing the fuel filter on your LBZ. Here are some detailed instructions to guide you through the process:

Before you begin, make sure you have the necessary tools and a new fuel filter that is compatible with your LBZ. It is also recommended to have a plastic bag or container to catch any spilled fuel.

Step 1: Accessing the Fuel Filter

• One way to access the fuel filter is by removing the passenger-side inner fender. You can use a specialised clip tool or a screwdriver to remove the pins holding the inner fender in place. Be careful not to damage the pins, as they can be tricky to remove.
• Another approach is to go through the top by using a bucket to get the right angle and an oil filter wrench to reach the filter. This method may require manoeuvring around hoses and lines.

Step 2: Removing the Old Fuel Filter

• Once you have access to the fuel filter, start by unplugging the water sensor (WIF) at the bottom of the filter. You may want to drain the fuel from the old filter into a container, but some people skip this step.
• Break the filter loose with your hands. Be careful not to spill fuel everywhere, as it can damage the rubber coating on your frame.
• Finish unscrewing the old filter by hand or with a filter wrench. You may need to use channel locks or a big wrench if it's too tight.

Step 3: Filling the New Fuel Filter

Take the new fuel filter and fill it with diesel fuel. This step ensures that the filter is primed and ready to function once installed.

Step 4: Installing the New Fuel Filter

• Take the old O-ring off the WIF sensor and put it on the new filter, along with a new O-ring. You can grease the O-rings with petroleum-based grease or diesel fuel to improve the seal.
• Screw the new fuel filter onto the filter head by hand. You don't need to overtighten it; just make sure it's hand-tight.
• Reconnect the WIF sensor and any other disconnected wires.

Step 5: Priming and Testing

• Locate the small black screw on top of the filter area and remove it temporarily.
• Pump the metal primer on top of the filter until fuel comes out of the screw hole. Then put the screw back in, being careful not to overtighten it.
• Start your LBZ and let it run for a few minutes. Check for any leaks around the new fuel filter. If there are no leaks, you're done!

Remember to dispose of the old fuel filter and any spilled fuel properly. Always refer to your vehicle's manual or seek professional assistance if you're unsure about any steps.

Bleed the fuel filter

Bleeding the fuel filter is a crucial step in changing the fuel filter on your LBZ. Here is a detailed guide on how to do it effectively:

Before beginning the bleeding process, ensure your fuel tank has enough fuel. It doesn't need to be full, but an empty tank can cause issues. The easiest method is to install an electric lift pump and turn it on. If you don't have one, you'll need to manually pump the primer on the fuel filter multiple times (around 50-100 pumps or so) until you feel more resistance.

Once you feel resistance, open the bleeder screw on the filter assembly. You can find this on the bottom of the fuel filter; it may be a bleeder tab. Continue pumping until airless fuel is present, then close the bleeder.

After closing the bleeder, continue pumping the primer until it becomes very hard to press. Try to start the engine. If it starts and then stalls, simply pump the primer again until it's hard, and try to start again. If it continues to stall after several attempts, you may have a leak that is letting air into the system.

If you have access to an air compressor with a good regulator, you can try an alternative method to save yourself some manual pumping. Apply low-pressure air (2-5 PSI) to the fuel filler. You can use a rag wrapped around the air nozzle or install a tire valve stem into a retired filler cap. Leave the bleeder open until fuel is present, then close it and proceed with the priming method described above.

Note: Be careful when handling the plastic bleeder screw. Even though it has a slot, use only a nut driver or socket, and don't overtighten. It should be snug, slightly more than finger-tight, as it is O-ring sealed.

Frequently asked questions