1994 S10 Blazer Fuel Pump Relay Switch

I have a 1994 S10 Blazer with the 4.3 vortec engine. After driving for a little while and shutting the vehicle off it doesn't start back up. I had my head next to the fuel tank when trying to start it and fuel pump does not turn on. If I let it sit for a little while it starts right up. Somebody had mentioned to me about the fuel pump relay switch. However, nobody seems to be able to tell me where it is. Some people say it's under the hood, other people say it's in the glove box, and other people say that it is behind the radio somewhere. Can somebody please help me......:banghead:

Under center of instrument panel may be a hair to drivers or passengers side.
Best to test for 12 volts to fuel pump gray wire.
If 12 volts there check for good ground.
And give it the old whack on botom of tank to wake up pump.
May be bad pump.
Does fuel pump gray wire have 12 volts when cranking and oil pressure comes up?