98 Blazer won't start

[teacherbull]

I have a 98 Blazer (4.3L V6) that wouldn't start for my wife several days ago. It would turn over, but not start. The fuel pump wasn't running so I switched the relay with the one for the AC. Still nothing, so I checked the fuse and it was fine. There was 12.5v on the battery,and I can't seem to find the red wire that's used for checking the fuel pump, so that wasn't done. I charged the battery just in case that was the problem, but the voltage didn't go up much.I figured it was probably the pump gone bad. I got the fuel tank down and checked the voltage to the pump - The wire that my diagram says is supposed to be the 12v source doesn't have any power, but the wire that is supposed to be fuel level sending unit has 5v when the key is on, and then goes off when the key is shut off. I put a voltmeter across where the 20a fuse is for the fuel pump (with the fuse out of it) and I get 12v. I was under the impression that this should read 0 when done. Does this tell me I have a short somewhere? If so can someone tell me if there are any usual culprits? I don't really think putting a new pump on is going to solve my problems, but if anyone else has any ideas, I'm open for input.

[DINO55]

Have you tried running a new 12v power source to your pump to see if it is the pump itself? also when you turn the key on, the fuel pump only runs for (2) seconds then stops.....

[old_master]

In the underhood fuse panel, there is an empty, recessed terminal, just in front of the fuel pump relay. That terminal goes directly to the fuel pump. Install a fused jumper wire from battery positive to that terminal and the pump should run continously. Disconnect the connector from the fuel pump, and you should show battery voltage at the grey wire.