The location of the fuel pump relay on a 1992 Chevy truck should be under the hood near the firewall on the passenger side of the truck.
There should be a cover that unscrews and wires should be under that cover along with the fuel pump relay.
The fuel pump relay is positioned between the coolant reservoir and the engine and is attached to the firewall under a cover.
The fuel pump relay is the larger black box type device.
It just unplugs from the connector and a new one plugs into it.
The relay can sometimes be stuck and not allow the fuel pump to operate.
The fuel pump comes on through use of the relay when you turn the key on and then turns back off unless you start the engine.