If the filter is installed in the fuel line, it is called an external filter; conversely, an internal filter refers to a filter installed inside the fuel pump and fuel tank. The fuel tank filter or its protective sleeve is generally considered maintenance-free.
Many imported vehicles use a banjo fitting for their fuel filters. To ensure a reliable seal, never reuse the same gasket. Even if a new gasket is used, it must be inspected for tightness after tightening. When replacing O-rings in the fuel system, ensure they are of the correct specification and model, and verify their elasticity and hardness.
A closed-loop fuel system has only one internal filter (inside the fuel tank). Although this all-in-one pump, filter, and delivery unit is expensive, it requires prompt and proper maintenance if fuel flow is obstructed or engine performance is compromised. Also, check all fuel lines for faults and cracks and crimping at hose clamps.
