I recently bougt a 92 extended can and have been trying to get it running. Well, Ive tracked the problem/or part of the problem of it not starting down to the fuel pump. I am getting power to the pump but its not working. I figured it was a bad pump, so I dropped the tank and tested it and it pumps exactly as it should. I then put it back in the tank and it then wouldnt work after bolting the tank back up. I dropped the tank again and tested it while it was still in the tank and it worked. I push the tank up the last six inches and then it wont work anymore. What could be causing it not to work when the tank is fully bolted? Thanks for the help

 

Look for any wire insulation that has rubbed through, and might be shorting or grounding to the frame. Also, you might have a broken wire that is losing continuity when flexed in it's normal position.

 

If it was shorted you would blow your 15 A. EFI fuse. I'd bet on a broken wire. First verify that the male and female connectors on each side of the tank connection are in good shape and are making a proper connection. Connect your voltmeter to the connector at the tank (body harness side), jumper +B and Fp at the check connector (data link connector 1), turn your key to the run position, establish that you are getting 12v at the connector. Watch the voltmeter, go along the harness route shaking and moving the harness or if you can't do both of these tasks at the same time get someone to help you. If you lose the voltage reading during this procedure, that will prove that you have a broken wire. If so check the wires at the connector first and then move toward the front of the vehicle. Untape the wires and slowly check them, watch the voltmeter all the time you are moving the wires and don't be decieved, by wires that look ok, I've seen the conductor strands break inside the insulation. If the wires check out in the harness, then set your meter on ohms and connect it to the fuel pump harness that goes into the tank. A good fuel pump should read around 37 ohms. Watch the ohm meter and move the tank harness around like you did the body harness. If you lose your ohm reading and the ohm meter goes to infinity (analog) or to overload (digital) that will indicate an open circuit and your broken wire is in this harness. If your wires check out, then the fuel pump may have an intermittent problem. A fuel pump is an electric motor and electric motors can develop bad segments on the armature. Each time the fuel pump stops there are armature segments directly across from the magnets. If one of these bad segments ends up directly across from one of the magnets, next time the fuel pump is turned on, it may not start, but the way that your's is acting; I'd still bet on the broken wire!

 

so... are you testing the pump with another battery? or just putting power directly to the pump? If you just doin the direct power trick, it means you have a good pump but have a fault somewhere else. It starts at your afm-cor relay-fuel pump.