A fuel pump filter is a filter that is either inside the housing of the fuel pump, or attaches to the fuel pump itself. Unlike fuel filters on a car with fuel injection, which are separate from the fuel pump and are replaced regularly as part of the routine maintenance on a car, a fuel pump filter is the part of a mechanical fuel pump assembly and usually does not need to be replaced except in extreme circumstances.
A fuel pump filter often consists of a coarse metal screen that is mounted inside of the fuel pump. The purpose of this screen is simply to stop any large particles from entering the system from the fuel tank. Volkswagen used a fuel pump filter for a while that was nothing more than a dome-shaped screen that sat in the very top of the fuel pump, beneath a cap-shaped housing.
Rather than replace this type of fuel pump filter, usually you will only need to clean the screen. Because the screen is coarse, by disassembling the fuel pump and removing the fuel pump filter, you can easily clean any particles out of the screen. The only times the fuel pump filter may need to be replaced is if the screen becomes damaged, preventing it from doing its job effectively, or if for some reason you are unable to clean it sufficiently.
Some other cars use a screw-on style of fuel pump filter, which is typically contained in a cylinder-shaped housing that screws directly onto the fuel pump. The metal housing contains a paper filter that can be disposed of and replaced when it becomes dirty; replacements can be purchased at most auto parts stores.
A fuel filter, on the other hand, is a part that is found on cars that have fuel injection systems. A fuel filter usually is situated along the fuel lines in the engine compartment, but can also be located in the back of the car, near the fuel tank. Instead of a coarse screen, the filter housing contains a finer material through which the fuel is filtered. This removes almost all particles from the fuel and keeps the fuel system in good working order. However, the finer filtering system also means that the filter is more likely to become clogged, and must be replaced regularly. Many mechanics recommend replacing a fuel filter every two years at a minimum, and every year when the vehicle is operated in extremely dirty conditions, such as in a city or on dirt roads.