1993 Chevy Cheyenne Possible oil pressure switch trouble?

If you think it is a fuel issue, use a gage and check fuel pressure. Some of the national brand auto stores used to loan out a fuel pressure gage, if you don't have one. As far as the oil pressure switch in the fuel pump circuit, that is a redundant power supply to the pump. As long as the fuel pump relay and circuits are functional, rpm signal present, engine cranking, the pump should run regardless of o/p switch. At the fuel pump connector, the gray wire is voltage for fuel pump motor. Any applicable trouble codes. You should be able to check mil codes, yourself.