My 1972 350sl won't start. I check to wires to fuel pump, not hot. If I run a set of jumpers back to the fuel pump it will start, and the wires that I disconnected are now hot. There is something stopping the motor from starting and allowing the fuel pump to start pumping. In a perfect world the car will start and 2 or 3 seconds later the fuel pump gets 12v to keep it running. Any help would be great.