A BMW E39's fuel filter should be changed every 30,000 miles or so, depending on the quality of gasoline normally used combined with the road conditions normally travelled upon. Dirt and debris build up in an engine's fuel filter, eventually creating a hesitation, grinding or stalling sensation—particularly if neglected. While hiring a mechanic is surely the cleanest way to get the job done, changing the filter yourself is an ideal way to save on labour costs.
Run your vehicle until the fuel gauge shows an absolute minimum amount of fuel left. The closer to empty your fuel tank is, the easier and safer the drainage process will be when you are actually under your car. You can begin working on your filter replacement when your gas is at less than a quarter-tank full.
Disconnect your BMW's battery by removing the negative (black) cable. This will prevent any potential sparks that could cause danger while working with the fuel tank.
Jack up the driver's side of your BMW on the rear end using a reliable jack. Use caution regarding the car's support. Putting the jack directly under floor boards can cause the jack to go right through the floor of your car, causing tremendous damage to your BMW and, even worse, bodily injury to you during the replacement procedure.
Look for a plastic panel in front of the fuel tank under your car. By removing this panel with a screwdriver, the fuel filter will be exposed. An arrow pointing toward the engine will be visible. This will be the location of your new fuel filter.
Clamp down the fuel lines using two pairs of locking pliers, more commonly known as vice grips. Use caution to not damage the fuel lines when clamping by squeezing too tight.
Gently loosen the hose clamps attached to the filter to remove the fuel lines. Some fuel may squirt out of the unit during this step, which is why it is essential to wear safety goggles.
Find the arrow on the new filter and attach the engine's fuel line to the side of the filter containing this arrow. Tighten the hose clamp to secure the filter.
Attach the other end of the filter to the line that goes to the fuel tank, again securing the hose in place by firmly clamping down. It is not necessary to overtighten, as this can cause greater damage to the fuel lines.
Remove the vice-grips as preparation for pushing the new filter back into the mounting bracket of the fuel system. As you mount the new filter back in place, remember that fuel is gradually flowing through the lines again, so caution should be taken to not force anything that could snap and cause a dangerous leak.
Replace the plastic panel that conceals the fuel system. Once the panel is reattached, the work beneath the car is complete and you can lower the jacks.
Re-connect the car's battery by attaching the black (negative) cable. This will allow you to start your engine and the fuel system to circulate the fuel throughout the new filter. You may need to crank your engine several times before it starts properly, but this is a normal reaction to the fuel-filter change. After a few starts, your engine should be running smoothly again.