GM-GMC: 1989 gmc 2500 4x4 350, fuel pump relay, fuelpump

Question
my fuel injection and fuelpump stoped working buy everything else worked so i put another computer in it and it worked for a few days and now it is doing the same thing but everything else works except the fuel pump and fuel injectors

Answer
Check the fuel pump output right at the pcm to see if the pcm is functioning correctly, same for your injectors.  Try swapping your fuel pump relay with another relay and see if your fuel pump starts working.  Double check all the pcm feeds and grounds also.
Hope this helps.