Changing Fuel Filter: Lml Duramax Guide For Diyers

The fuel filter in a Duramax engine should be changed every 15,000 miles for 2001-2010 models, and every 22,500 miles for 2011-2016 models. The process of changing the fuel filter involves removing the inner fender and air intake tube, disconnecting the water-in-fuel sensor electrical connector, and replacing the filter and gasket. It is important to note that the fuel system should be bled of air before starting the vehicle to avoid placing additional strain on the high-pressure injection pump.

The fuel filter is located on the passenger side of the engine

Now, you should be able to see the fuel filter from the passenger side. Disconnect the Water In Fuel (WIF) connector and let it hang. You can then proceed to unscrew and remove the fuel filter. This can be done by hand if you are strong enough, or with a strap wrench.

Once the fuel filter is removed, dispose of the contents inside the filter properly. Using a WIF wrench or channel locks, remove the WIF sensor. The new filter will come with new O-rings, so be sure to remove and discard the old ones. Lubricate the O-rings with some 2-stroke oil, and don't be shy about using it.

With the fuel filter and WIF sensor back together, you can now reinstall the filter. This part can be a little frustrating, as it is in an awkward position and it can be hard to get the filter threaded on. Be patient and it will thread eventually. 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. 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 fuel filter. This will take a lot of 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 tighten down the bleeder screw. After tightening the screw, keep pumping the primer until it gets very hard to pump. You should now be able to wrestle back on the inner fender liner.

The fuel filter housing has an integrated fuel plunger to prime the fuel system

The fuel filter housing is located on the passenger side of the engine. It features an integrated fuel plunger to prime the fuel system after replacing the fuel filter. This is necessary to bleed the fuel system of air after installing a new filter. If you have a 2001 to 2016 Duramax diesel vehicle, you will need to do this as these models do not have an electric lift pump.

Failing to bleed air from the fuel system before starting the vehicle can cause issues. Air in the fuel system can interfere with fuel delivery and engine operation, placing additional strain and excessive wear on the high-pressure injection pump. Therefore, it is important to prime the fuel system after replacing the fuel filter.

To prime the fuel system, locate the bleed valve on the driver's side of the fuel priming pump. Open the bleed screw and pump the plunger on the top of the fuel filter housing repeatedly until all the air escapes and diesel fuel begins to flow out of the bleed screw orifice. Tighten the bleed screw—but not too much, as it is made of plastic—and clean up any spills.

After priming the fuel system, you can reinstall the inner fender and intake tube. Start the engine and check for leaks. If the truck runs rough for an extended period, turn off the engine, re-bleed the system at the fuel filter housing, and check for leaks again.

The water-in-fuel sensor assembly should be checked

The water-in-fuel sensor assembly is an important component of the fuel system in a Duramax diesel engine. It is designed to detect the presence of water in the fuel and alert the driver through a warning light on the dashboard. Here are some detailed instructions and information on checking and maintaining the water-in-fuel sensor assembly:

Location and Access:

The water-in-fuel sensor assembly is located at the bottom of the fuel filter, which is positioned on the passenger side of the engine, below the air intake tube. To access the sensor assembly, you will need to remove the center air intake tube and the passenger-side inner fender. The inner fender is secured by plastic body clips, which tend to break easily, so it is recommended to replace them if removal is necessary.

Checking and Maintenance:

• Before starting, ensure you have a replacement o-ring for the water-in-fuel sensor assembly. This o-ring is typically provided with a new fuel filter.
• Attach a small section of 1/4" fuel hose to the water-fuel separator drain valve at the bottom of the fuel filter.
• Open the bleed screw at the top of the fuel filter housing to release any built-up pressure.
• Drain the water separator into a suitable container and properly dispose of the drained fuel.
• Close the drain valve and remove the fuel hose.
• Locate and disconnect the electrical connector of the water-in-fuel sensor.
• Remove the fuel filter by rotating it counter-clockwise, being careful not to entangle the sensor wire. Keep the filter upright to avoid spilling fuel.
• Drain the removed fuel filter and verify that the gasket did not stick to the fuel filter housing flange.
• Using an appropriate tool, remove the water-in-fuel sensor assembly from the bottom of the fuel filter.
• Inspect the water-in-fuel sensor assembly for any damage. If it is damaged, do not reuse it.
• Clean and lubricate the o-ring on the sensor assembly with engine oil and install it onto the new fuel filter. Ensure it is snug but not overtightened.
• Lubricate the new fuel filter gasket with engine oil and install it at the top of the fuel filter assembly.
• Reinstall the inner fender and intake tube.
• Start the engine and check for any leaks. If the engine runs rough for an extended period, turn it off, and re-bleed the system at the fuel filter housing.

Troubleshooting:

If you encounter a "Water in Fuel" warning light, there are a few potential causes and troubleshooting steps to consider:

• Check the water-in-fuel sensor itself. Ensure it is functioning properly and not damaged.
• Drain the fuel filter and inspect for the presence of water. If there is no water, the sensor may be faulty.
• Inspect the wiring and connectors of the sensor for any signs of damage or corrosion. Ensure the connections are secure.
• Consult a qualified mechanic or dealership for further diagnostics and repair if the issue persists.

It is important to regularly maintain and inspect the water-in-fuel sensor assembly to ensure the proper functioning of your Duramax diesel engine. Following the recommended maintenance intervals and procedures can help prevent issues and ensure the longevity of your vehicle.

The fuel filter should be drained and the gasket checked

Draining the fuel filter and checking the gasket is a crucial step in maintaining your LML Duramax engine. Here's a detailed guide on how to perform this task:

Draining the Fuel Filter:

• Remove the center air intake tube: Locate the fuel filter on the passenger side of the engine, below the air intake tube. Start by removing the center air intake tube, which is positioned between the air filter housing and the turbocharger inlet mouthpiece.
• Remove the passenger side inner fender: The inner fender is secured by plastic body clips. Carefully remove it to access the fuel filter housing assembly.
• Optional: For a more controlled drain, attach a small section of 1/4" fuel hose to the water-fuel separator drain valve at the bottom of the fuel filter.
• Open the bleed screw: Locate the bleed screw at the top of the fuel filter housing and open it. This will allow you to drain the water separator. Have a suitable container ready to collect the drained fuel.
• Drain the water separator: Ensure the container is suitable for holding fuel, then drain the water separator by opening the drain valve.
• Close the drain valve and remove the fuel hose: Once the draining is complete, close the drain valve and remove the fuel hose if you used one.
• Disconnect the water-in-fuel sensor electrical connector: Locate and disconnect this sensor to prepare for the next step.
• Remove the fuel filter: Rotate the fuel filter counter-clockwise, as seen from the bottom up. Be careful to not entangle the water-in-fuel sensor wire during this process. Keep the filter upright to avoid spilling fuel.
• Drain the removed filter and check the gasket: Once the filter is removed, drain it and perform a crucial check. Verify that the gasket, a crucial sealing component, has not stuck to the fuel filter housing flange. Ensure it is intact and in good condition.

Replacing the Fuel Filter:

• Remove the water-in-fuel sensor assembly: Use a wrench, socket, or pliers to remove this assembly from the bottom of the fuel filter. If it is damaged, do not reuse it.
• Replace and lubricate the O-ring: The new fuel filter will come with a replacement O-ring for the water-in-fuel sensor assembly. Lubricate this new O-ring with clean engine oil and install it snugly onto the new fuel filter. Do not overtighten it.
• Lubricate the new fuel filter gasket: Before installing the new fuel filter, lubricate its gasket with clean engine oil as well.
• Install the new fuel filter: Ensure the water-in-fuel sensor connector doesn't get entangled. Install the new fuel filter snugly by hand; do not use tools to tighten it.
• Locate and open the bleed valve: Find the bleed valve towards the driver's side of the fuel priming pump and open it. If desired, remove the bleed screw for inspection and cleaning.
• Pump the plunger to remove air: Repeatedly pump the plunger on the fuel filter housing until all air escapes, and diesel fuel starts flowing out of the bleed screw orifice.
• Close the bleed screw: Once diesel fuel flows out, immediately close the bleed screw. Do not overtighten, as the screw is made of plastic. Clean up any spills to easily detect leaks.
• Reinstall the inner fender and intake tube: Put back the inner fender and intake tube, preparing for the engine start.
• Start the engine and check for leaks: Turn on the engine and carefully monitor for any leaks. If the truck runs rough for an extended period, turn off the engine, re-bleed the system at the fuel filter housing, and re-check for leaks, including around the bleed screw O-ring.

The o-ring on the water-in-fuel sensor assembly should be replaced

When replacing the fuel filter on a 2001-2016 Duramax Diesel, it is important to replace the o-ring on the water-in-fuel sensor assembly. This is because the o-ring is prone to allowing air to bleed into the fuel system, which can cause the fuel system to lose its prime. This can result in extended cranking after the truck has been sitting for long periods, or the engine starting and then dying. If the problem worsens, it may even become impossible to restart the truck without manually priming it when parked on an incline.

To replace the o-ring on the water-in-fuel sensor assembly, follow these steps:

• Remove the water-in-fuel sensor assembly from the bottom of the fuel filter using an appropriate wrench, socket, or pliers.
• Replace the o-ring on the water-in-fuel sensor assembly. This should be provided with the new fuel filter. If the water-in-fuel sensor assembly is damaged, do not reuse it.
• Lubricate the new o-ring with clean engine oil.
• Install the o-ring snugly onto the new fuel filter, ensuring it is not overtightened.

By replacing the o-ring on the water-in-fuel sensor assembly, you can help prevent air leaks in the fuel system and maintain the proper functioning of your Duramax Diesel engine.

Frequently asked questions