Changing Fuel Filter In Lb7 Duramax: Step-By-Step Guide

Changing the fuel filter on a Chevy or GMC Duramax is a simple task that can be done in under 10 minutes. The fuel filter is located near the firewall on the passenger side of the engine. To change the filter, you will need a panel clip remover, a Water In Fuel sensor wrench (or channel locks), a 1/2-inch nut driver, and some 2-stroke oil to lube up the o-rings. Start by removing the pins that hold the inner fender well liner in place, then disconnect the WIF connector. Unscrew the fuel filter and remove it, then remove the WIF sensor. Lubricate the new filter's o-rings and install it, then go to the engine and loosen the bleeder screw. Prime the fuel filter until diesel fuel comes out, then tighten the bleeder screw and continue pumping the primer until it becomes very hard to pump.

Removing the old fuel filter

To remove the old fuel filter from your LB7 Duramax, you will need a panel clip remover, a Water In Fuel (WIF) sensor wrench or channel locks, a 1/2-inch nut driver, and some 2-stroke oil to lubricate the O-rings.

Start by popping the hood and sitting by the passenger-side tire, looking at the fender well. Using the panel clip remover, remove the pins holding the inner fender well liner to the truck. With the pins removed and the wire harnesses pulled out, set the liner aside.

Now you should be able to see the fuel filter. Disconnect the WIF connector and let it hang. You can now unscrew and remove the fuel filter. This may be possible to do by hand, but if not, use a strap wrench.

Dispose of the contents inside the filter properly. Using a WIF wrench or channel locks, remove the WIF sensor. Discard the old O-rings and replace them with the new ones that come with the new filter. Lubricate the large O-ring and the outer edge of the filter where the O-ring will be placed with 2-stroke oil. Don't forget to replace the little O-ring on the WIF sensor as well, lubricating it first.

With the new fuel filter and WIF sensor reassembled, you can now put the filter back into the truck. This can be a little frustrating, as it is an awkward position, and it's hard to get the filter threaded on. Be patient and tighten the filter as recommended (1/3 to 1/2 turn after the seal has made contact).

Now, go back to the engine and look at it from under the hood. You will see the filter pump and bleeder screw. Loosen the bleeder screw with a 1/2-inch nut driver (do not take it out all the way, just enough to let air out). With the bleeder screw loosened, you can begin priming the new fuel filter. This will take about half a million pumps, so be patient. You will hear air coming out of the screw, and eventually, diesel fuel will start to come out. When this happens, press down on the primer pump and hold it, then tighten down the bleeder screw (be careful not to over-tighten). After tightening the screw, keep pumping the primer until it becomes very hard to pump. You should now be ready to start the truck.

Installing the new fuel filter

Now you can install the new fuel filter. Make sure to lubricate the O-rings with some 2-stroke oil and don't be shy about using it. Also, don't forget to replace the little O-ring on the WIF sensor. With the Fuel Filter and WIF sensor back together, it is now ready to go back into the truck. This part can be a little frustrating as it is in an awkward position and it's hard to get the filter threaded on. Be patient and it will thread its way on. Tighten down the filter as recommended (1/3 to 1/2 turn after the seal has made contact).

Now go back to the engine and look at it from under the hood, and you will see the filter pump and bleeder screw. Loosen the bleeder screw with a 1/2-inch nut driver (do not take it out all the way, just enough to let air out). Now, with the bleeder screw loosened, you can begin priming the fuel filter. This will take about half a million pumps, so be patient. You will hear air coming out of the screw, and eventually, diesel fuel will come out. When that happens, press down on the primer pump and hold it, then, with the other hand, tighten down the bleeder screw (warning: do not over-tighten). And, after tightening the screw, keep pumping the primer until it gets very hard to pump. It will be almost impossible to pump anymore after that.

Lubricating the O-rings

Before beginning the lubrication process, it is essential to have the necessary tools and materials ready. For this specific task, you will need a suitable lubricant, such as 2-stroke oil or diesel fuel, and clean rags or towels for wiping away any excess lubricant. Having these items on hand will make the process more efficient and help you avoid any last-minute searches for missing items.

Now, let's get started with the lubrication process:

• Remove the Old O-rings: Before lubricating the new O-rings, it is crucial to remove the old ones from the fuel filter. Carefully pry or peel them off, ensuring that you don't damage the sealing surfaces of the fuel filter or the WIF (Water In Fuel) sensor. Removing the old O-rings is essential to ensure a clean surface for the new ones.
• Clean the Sealing Surfaces: Once the old O-rings are removed, take a moment to inspect and clean the sealing surfaces. Use a clean rag or towel to wipe away any dirt, debris, or residue that may be present. This step is important to ensure that the new O-rings have a clean and smooth surface to seal against.
• Lubricate the New O-rings: With the sealing surfaces clean and dry, it's time to lubricate the new O-rings. Take one of the new O-rings and dip it into your chosen lubricant (2-stroke oil or diesel fuel). Ensure that the entire O-ring is coated with a thin layer of lubricant. This step will help the O-ring slide into place more easily and create a better seal.
• Install the Lubricated O-ring: After lubricating the O-ring, quickly place it onto the fuel filter or WIF sensor, ensuring it sits securely in the correct position. The lubrication will allow the O-ring to slide into place smoothly. Be careful not to stretch or deform the O-ring during installation.
• Wipe Away Excess Lubricant: Once the O-ring is in place, use a clean rag or towel to wipe away any excess lubricant that may have squeezed out. It is important to remove any excess lubricant to prevent drips or messes. At this point, you can repeat the process for any additional O-rings that require lubrication.
• Reinstall the Fuel Filter: With the O-rings lubricated and in place, you can now proceed to reinstall the fuel filter. Follow the manufacturer's instructions or a reliable guide for reinstalling the fuel filter correctly. Ensure that all connections are secure and tight to prevent leaks.

By following these steps and paying attention to detail, you can effectively lubricate the O-rings when changing the fuel filter in your LB7 Duramax engine. Remember to take your time, work in a well-ventilated area, and wear appropriate safety gear, including gloves and eye protection, to ensure a safe and successful maintenance experience.

Priming the fuel filter

To prime the fuel filter, first loosen the bleeder screw with a 1/2-inch nut driver. Be careful not to take it out all the way—just loosen it enough to let air out. With the bleeder screw loosened, you can now begin priming the fuel filter. This will take about half a million pumps, so be patient. You will hear air coming out of the screw, and eventually, diesel fuel will start to come out. When this happens, press down on the primer pump and hold it, then tighten the bleeder screw with the other hand. Be careful not to over-tighten. After tightening the screw, keep pumping the primer until it becomes very hard to pump. You will know you are done when it is almost impossible to pump anymore.

Reattaching the fender well liner

To reattach the fender well liner, you will need to follow these steps:

Firstly, ensure that you have removed the old fuel filter and installed the new one. Once this is done, you can begin the process of reattaching the fender well liner.

Using the panel clip remover, you will need to re-insert the pins that hold the inner fender well liner in place. Make sure to securely fasten the liner back into position, ensuring that all wire harnesses are properly connected and tucked away.

Next, reconnect the Water In Fuel (WIF) sensor connector. This is an important step, as the WIF sensor plays a crucial role in monitoring the water level in your fuel system.

After ensuring that the WIF sensor is securely connected, you can proceed to tighten the fuel filter by hand or using a strap wrench. It is important to be patient during this step, as it can be a little tricky to get the filter threaded back on.

Once the fuel filter is securely tightened, you can move back to the engine and locate the filter pump and bleeder screw under the hood. Loosen the bleeder screw with a 1/2 inch nut driver, being careful not to remove it completely. Just loosen it enough to allow air to escape.

Now, you can begin priming the fuel filter. This step may take some time and effort, as it requires multiple pumps. You will hear air escaping through the screw at first, and eventually, diesel fuel will start to come out. Once this happens, press down on the primer pump and hold it while tightening the bleeder screw with your other hand. Be careful not to over-tighten the screw.

Finally, continue pumping the primer until you feel resistance and it becomes challenging to pump. At this point, you can stop pumping, and your fuel filter change is almost complete.

Now, you just need to reattach any remaining components and start your engine. Ensure that you dispose of the old fuel filter and its contents properly, following local regulations for hazardous waste disposal.

Frequently asked questions