If your not 100% sure its the pump or the wiring, Why not fit a second fuse directly before the pump.

That way if it blows the first one, you know its a wiring fault, it it blows the second one, its got to be the pump. ?

How much current does the pump take. ?? If its only 5/6 Amps max, You could fit something like a 10 Amp fuse near the pump and if it takes that one out first its likely to be the pump causing the problem and its a little bit safer.

( if it more than that you could fit a 20 amp at the front and a 15 amp at the rear )

Theres always a possibility that fitting anything larger than the the rated fuse could cause the wiring to burn out rather than blow the fuse but you need a definite diagnosis to save hours or days of unecessary labour.

( In fact it doesn't always need a larger fuse to burn the wiring out it can do it with a standard fuse )

Always a Scarey thought of shorts and sparking inside fuel tanks but its supposed to be relatively safe. ( As long as its not in my fuel Tank )

H.T.H. Tony.