By chance do you have dual fuel tanks ? I have seen the switch go bad .
some early GM's had wire harness problems as the the early blazers where the harness goes just below the toe board of the fire wall . Have you had someone turn the key and go to the tank to see if you can hear the pump running remove you gas cap and and put your ear up to it and had have a helper turn the key on It could just be a bad pump , did you check the ground wire in the harness where the wires go to the pump ? If you give it a short shot of starting fluid and it kicks over I would pull the pump the only other thing could be is a clogged fuel filter .... Fuel pressure regulator ..