got a 1994 Isuzu Trooper that quit running, fuel pump wasnt running, took out the pump and checked it and works good, checked the relays,and fuse and they good too, but when hook fuel pump back up in tank fuel pump wont run??

Most bad pumps will run out of the tank in the open air,but when putting back in fuel which is heaver than air they will not run. The pump is bad replace it.