Part of routine maintenance on a Volkswagen Jetta TDI is replacement of the fuel filter for the high pressure injection system. If the fuel filter becomes clogged with dirt and debris, the car will not return optimal fuel mileage and may run rough and eventually may not run at all. The fuel filter on a TDI should be replaced every 20,000 miles.
Open the hood. The fuel filter is located on the passenger side of the engine bay in front of the coolant overflow bottle. Squeeze the fuel lines hose clamps with the pliers and slide the clips off of the lines. Push the fuel lines off of the metal lines on the filter.
Remove the fuel filter clip, which is located where two of the fuel lines come together and go into the filter. Lift the filter “tee” out of the filter. Loosen the screw on the sleeve clamp that holds the filter body in place in the engine bay. Remove the filter.
Fill the new fuel filter with fresh diesel fuel. This will help ensure that there is no air in the fuel system when you install the new filter. Wear rubber gloves. Install the new filter on its base in the engine bay and tighten the clamp.
Remove the old o-rings on the plastic tee that goes in the filter. Use a small screwdriver to remove the o-rings and then install the new ones carefully. Install the tee into the new filter and reinstall the clip that holds the tee in place. Slide the other fuel lines onto the lines on the filter. Install the clips that hold the fuel lines to the filter.
Start the car and bring the RPMs up to 2,000 to 2,500 for a minute or so to clear any air out of the system.
