My cosworth has been playing up like a right bastard lately miss firing and so on but now my brake pedal has gone rock solid so I cant road test it to sort the misfire.

Iv traced the problem back to the relay and basically im getting power from the battery, im getting an ignition power and if I put a live to the pump feed it kicks in. when I earth the relay out the pump kicks in but it wont stop until I remove the earth iv put on. This make me think that the earth for the relay must be switched by some sort of pressure swith on the pump itself. But to be honest im crap with electrics and I could be totally wrong! Lol

Can anyone tell me how the relay is controlled? Am I right in thinking there could be a faulty swith on the pump?