When my 1981 truck gets to temp, the fuel pump has been quitting on me. I've tried different fuel pump relays--no change. When I jumper the relay socket, the pump runs and I can move on down the road. Before the engine reaches temp, and after it cools down, the engine runs normally. I'm thinking the coil, the fuel pump itself (overheating?), the warm pressure regulator, the wiring from fuel pump to coil, or? Any ideas?