Almost everyone that works on a car will groan when they encounter this type of situation. There is a short somewhere that can be anywhere along almost the length of the car. Water may have leaked into the back of the fuse box and be causing a short there. The wire that travels back to the fuel pump might have rubbed off its insulation anywhere along its length and is shorting against some metal. The wire connector to the fuel pump could be bad. The fuel pump itself could be bad. It comes down to getting a good voltmeter and traveling along that length eliminating what is good till you find what is bad.