Often called the “sock” or strainer, the fuel pump filter is the first line of defense located inside the fuel tank, attached directly to the inlet of the fuel pump. It traps large rust particles, dirt, and sediment settling at the bottom of the tank before they can enter the pump mechanism. Unlike the inline fuel filter (which is finer), this filter protects the pump itself from seizing. If it becomes clogged, the pump has to work harder to draw fuel, leading to pump overheating and eventual failure.