golf gti cab fuel inj problem..keeps blowin fuses

i have a 1990 mk1 golf gti karmann cab which i rescued last year from someones garage...since then i managed to get it running perfectly but it has had an intermittent fault on the fuel pump relay...i think a loose connection on the board maybe but last weekend it just stopped...i have traced the problem to the no5 fuse on the board which just keeps blowing when you start the engine after about 5 secs..im not sure wether there is another fuel pump in or near the tank which maybe the cause ...can anyone help ????