1997 GMC Suburban Fuel Pump

Without dual tanks, there is an oil pressure switch in the fuel pump circuit. Once you crank it enough to build oil pressure and the switch closes, the pump will run, even without the relay. As long as the o/p circuit is functional.

Use a testlite and check that the fuse circuit is hot, ecmB mini fuse 20 amp, under the hood.

There should be a fuel pump test connector, 5.7L gas engine. Underhood, driverside, close to firewall and relay pack, red wire with connector, nothing plugged into it. If you use a jumper wire and run B+ to the connector, the pump should run. You don't have to use the key. Use an inline fuse on the jumper. If the pump won't run, check for voltage at the pump connector, gray wire, if no voltage, something wrong with wiring circuit.

The pcm sends voltage to the coil side if relay, in order to energize, green wire with white tracer. At initial prime, key on engine off, the pcm may energize the relay for couple second, then without rpm signal, engine cranking, the pcm won't energize the relay or injectors. But, with the o/p switch in the pump circuit, and the switch circuit is functional, the pump will run and make pressure, regardless of the relay.

Did you check ground at the pump connector? If you have good voltage and ground at the pump and no pump action, sounds like the pump. Let us know.