I own a 91 silverado k1500 the fuel pump works but will not run with key in start position or run position

 

a realay would be my first guess

 

relay bad. relay should be on firewall near brake master cylinder

 

we've tried 3 different relays and tested everyone to make sure they work which they do i can jump it from various places including the OBD 1 connecter which has to go through the relay to make the pump run power it up with the relay unplugged you get nothing