I have a topkick with 366 altanater shorted out burned batt altanater up and i replaced fuel pump got ecm from savage yard put it in it run better than it ever did for about 30 min and quit fuel pump ain't working again what could be problem.

SOURCE: Ram 1500 stalls after 15-20 mins. starts again after sitting

try the fuel filter

SOURCE: 2000 chevy silverado 1500 4.3 eng

Chevy Trucks, Blazers, S10 pickup and the like will vapor lock ecspecially the 2000 models. Do not tighten the gas cap past 1 click. There is a tube that runs from the top of the tank down and this gets hot and collapses or burns in half. We just bought a reinforced rubber tube cut it to lengh and use it instead of part and it's worked grat for 2 years so far.

SOURCE: truck wont start keeps blowing the ecm batt fuse

You have a short (bear wire) somewhere. Trace the wire and find it.
Have a great evening

SOURCE: Both fuel pump relays run

I think the fuses are overheating. Have you tried replacing them.

SOURCE: no power to fuel pump car was running fine just

Check for 12 volts power at the fuel pump harness. If no power is going to the pump, check the fuel pump relay. Also, check the fuel pump inertia switch. Ford usually has it on either inside left or right rear trunk fenders.