1987 Chevy Silverado

That is all it is meant for. It does not operate anything else.

Forgot to mention, you have only one fuel pump, not one for each tank.

Well my truck contains two fuel pumps(one in each tank).I have checked fuel pumps, I have replaced the fuel pump relay switch. The truck isnt recieving fuel to the fuel injectors or throtle body. The computer on the truck isnt giving information on the status of the truck. The computer is working properly because it gives me the diagnostic code (which is 12). I have run a hot wire form battery to both fuel pumps and I hear them both come on. Only if I run the hot wire from the battery to the fuel pumps.

Sorry guy. Mine only has one and is not fuel injected, thats what I was going on. Could be inline gas filters, but I'm sure you've checked that. When you hot wire each pump, does fuel come out the line going to the injectors?

Yes, the fuel does come out of the line. The switch that switches between the tanks has five wires going to it. When I un-plug the switch the gas hand goes counter clockwise way past the fuel mark. When I plug it back up it goes back to the fuel mark. How many volts should the fuel pumps be recieving? I am only getting 8. Something is telling the truck n ot to send fuel to the fuel injection system. The battery went bad in the truck. Before that battery went bad evrything was working properly. When I replaced the battery is when the fuel system stopped working properly. The truck turns over, the blinkers work, the lights work, etc. Everything works except the fuel system.