Numerous cause including a electrical short, too much current draw, bad wiring or bad fuel pump will cause the fuel pump fuse to blow. The main purpose of a fuse is to protect the circuit; it will open (break) the circuit if the current exceeds a safe level—on the order of about 15-20 amps for fuel pump circuits. If the fuel pump tries to draw too much current, it blows the fuse and the pump loses power and the engine either stalls or fails to start.
Most often, there are electrical shorts in the fuel system or wiring. In a short situation, the wire gets exposed and comes in contact with metal, causing current to flow from an unintended path. Wires that have been corroded or damaged will pose a higher risk of a short circuit, with worse susceptible wiring insulation on vehicles older than 10 years old. Mechanics say between 20 and 30 percent of blown fuses in fuel systems are caused by wiring problems — so thoroughly examining any fuel pump wiring as part of regular scheduled maintenance is key.
Another cause of blowing fuses is a failed or dirty fuel pump. Fuel pumps tend to work harder as they age or reach obstructions, siphoning more energy to keep the desired pressure level, commonly 40-70 PSI. This will create a greater load than the circuit was designed for, and the fuse will blow as a precaution. Research indicates that pumps under load can pull an additional 10-20% in increased current draw, greatly increasing the potential for blown fuses.
A relay malfunction could be another possible reason. The fuel pump relay controls power to the pump, and if it begins to fail, it may cause an intermittent power surge, which will cause the fuse to blow. In extremely high-mileage vehicles, components can also break down because of age, so testing the relay and fuse for proper function can diagnose the source of the issue.
As longtime automotive expert Ed China puts it: “Electrical integrity is key to fuel system function.” Maintaining good wiring, fuses, and relays can help keep the fuel pump running properly, without premature failures.
A good quality Fuel Pump and checking the electrical components related to the fuel system regularly help avoid fuses from blowing that helps performance stay up and minimizes the chances of unexpected in-operable states on the road.