bronco fuel problems

I have a 1989 bronco with automatic and the 5.0 in it. I fried out a relay and replaced it still no power to the fuel pump unless i use a jumper 3 relays and they were all brand new and tested ok. But even with a jumper the pump runs and get fuel to the rail but only runs for a second maybe two. Any ideas here? EEC? Map Sensor? Bad ground? I am so lost on this one.:runaround::crying:

tried inertia switch relays tested everything I can think of and what haynes manual says as well as replaced some of the harness that was corroded

The pump will only run until it builds up pressure. Then, it will turn off. You might have to rewire the pump from the relay. With new relays and whatnot you are still not getting power to the pump. The wiring is probably fried.