Replacing The Fuel Filter On A 2Nd Gen 12-Valve Cummins Engine

The 2nd Gen 12-valve Cummins engine was used in the 1994-1998 Dodge Ram 2500/3500 model trucks. The fuel filter is located just to the passenger side of and slightly below the brake booster. Changing the fuel filter can be done without having to lie on your back and can be achieved by first unclipping the WIF (Water in Fuel) wire from the wire harness. A small drip pan should be placed under the filter to catch any fuel that spills when the WIF sensor is unscrewed. The filter can then be unscrewed and removed. A new gasket should be installed in the filter housing, and the WIF sensor and gasket should be changed. The new filter should be empty when it is repositioned, and a funnel with a twist-shut-off and a long clear tube can be used to fill the new filter with fuel. Once full, the filter can be screwed back into the housing, and the WIF wire can be clipped back into the harness.

Unclipping the WIF wire

To unclip the WIF wire, lean over the fender and position yourself as if you are hugging the brake master cylinder. Then, carefully unclip the WIF (water in fuel) wire from the wire harness.

Now, hold a small drip pan under the filter to collect any fuel that spills out. You can use a small Tupperware container for this. Drain a small amount of fuel by unscrewing the WIF sensor. Close it back up, then unscrew the filter and rest it down in the little pocket between the frame and motor mount.

Reposition the filter and sneak it through the wires to remove it. Change over the WIF sensor and gasket, and put a new gasket in the filter housing.

Draining the fuel

First, locate the WIF (water in fuel) wire that is clipped to the wire harness. Unclip this wire and set it aside. Now, position a small drip pan or container underneath the fuel filter to catch any fuel that is drained. You don't want this spilling onto other components or the ground. With the drip pan in place, carefully unscrew the WIF sensor to drain a small amount of fuel. You only need to drain enough so that when you twist the filter to remove it, fuel doesn't spill everywhere. Once you've drained a small amount, close the WIF sensor back up.

Now, it's time to remove the fuel filter. Carefully unscrew it and rest it down in the pocket between the frame and the motor mount. You may need to reposition your hands and manoeuvre the filter through the wires to get it out. With the old filter out, you can now install the new filter. It is important that the new filter is empty, as this will make it much easier to install. Place the new filter in the same location as the old one, between the throttle linkage, starter, and throttle cable.

At this point, you can now fill the new filter with fuel. Using a funnel with a long, clear tube attached, slowly fill the new filter. Once it is full, carefully lift it and screw it back into the housing. Make sure to clip the WIF wire back into the harness, and you're done! By draining a small amount of fuel first and using an empty filter, you've avoided a messy situation and made the whole process much easier.

Removing the old filter

The first step in changing the fuel filter on your 2nd Gen 12 Valve Cummins is to locate the filter itself. It is positioned just to the passenger side of and slightly below the brake booster.

Now, lean over the fender and unclip the WIF (Water in Fuel) wire from the wire harness. You will need to hold a small drip pan under the filter to catch any fuel that spills out. By unscrewing the WIF sensor, you can drain a small amount of fuel. Close the sensor back up and then unscrew the filter. Rest the filter in the little pocket between the frame and motor mount. Reposition your hands and carefully sneak the filter through the wires to remove it fully.

Next, you will need to change over the WIF sensor and gasket and put a new gasket in the filter housing.

Installing the new filter

To install the new filter, first ensure that it is empty. Then, sneak it through the wires, positioning it between the throttle linkage, starter, and throttle cable. Next, you will need a funnel with a twist shut-off and a long clear tube. Fill the funnel with fuel and run the tube through the fuel lines down to the filter. Now, slowly twist the valve open and start filling the filter with fuel. Once full, lift the filter up and screw it back into the housing. Finally, clip the WIF wire back into the harness.

Refitting the WIF wire

When refitting the WIF wire, it is important to ensure that the wiring does not get all wrapped up and tangled around the filter wrench. This can be a common issue and cause frustration when trying to loosen the filter. One way to avoid this is by using a sawed-off broom handle to prime the lift pump, so you don't have to reach down and potentially get tangled up.

If you are experiencing issues with your WIF sensor, such as leaking fuel, there are a few options to consider. One solution is to use a thicker O-ring to stop the leaking. You can also look for a fuel filter that doesn't have a WIF sensor, such as the AirDog or FASS lift pump. Alternatively, you can simply plug the WIF sensor using a billet aluminium plug, which is a handy solution to stop the fuel leak.

When refitting the WIF wire, make sure to check the O-rings and replace them if necessary. It is also a good idea to clean the pre-filter screen regularly and replace it every 100,000 miles or so. This will help prevent any larger chunks of dirt or debris from reaching the lift pump and causing issues.

Finally, when refitting the WIF wire, be mindful of the wiring routing to ensure it doesn't interfere with any other components. You may need to loosen the fuel filter head mounting bolts to get the necessary clearance when installing the new filter.

Frequently asked questions