van cutting out and starting problem

hi there

our workshop has a fiat scudo that's decided to play up recently. it's a '97 1.9 turbo diesel.
basically the keypad and connection have been steadily deteriorating for a while and the vehicle has developed a non-start/cut-out problem that has become worse over time. we got a new keypad but that's become unreliable too and we want to get rid of it completely. the van doesn't start at all anymore. has anyone here done this before, and could you tell us how to modify the pump wiring? thanks in advance
shrek