I've got what I think is a 1985 f350 dump truck w/ that has an in tank electrical fuel pump, it only has one tank, and one pump, the front one, and the pump just is not running. The connector to the pump has 4 wires and if you are viewing the connector upside down with wires coming toward you like below. Sorry for bad illustration, couldnt get phone to cooperate and fork over the photo. I'd like to test voltage but want to make sure i know what each wire does and couldn't find anything online. Can anyone tell me what each wire is? Thanks.
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Bk Yw Pnk Rd

 

Wire colors fade after many years.

The two heavier wires will be for the pump. The diagram shows red and orange.

The two smaller wires will be for the sending unit. The diagram shows darkblue/yellow stripe and black.

 

On some of these non EECIV models with carburetors and tank pumps, the pump does not run with the key on unless the engine is running. When running, the pump power relay is powered by a closed oil pressure switch. To start the engine, power is applied to the pump by the starter solenoid. If so, you would probably see a fusible link hooked to the solenoid. This power bypasses the pump relay while the engine is cranking over supplying full power to the in tank fuel pump in start mode. (The pump relay supplies lower voltage during the run mode) You could probably disconnect the fusible link and apply power to it. With 12V power, the pump in the tank should be running. Since even tiny sparks are dangerous, I would use my remote starter switch or something similar to avoid them. Another option to safely apply power to the fusible link would be to remove the starter motor cable so the engine won't crank and use the solenoid and key to turn on the power. Listen for the pump. Of course, the fusible link would need to be good.

Another suggestion: Fixing your issue may be as simple as pushing the red button on your inertia switch. This switch is used to cut power to the electric fuel pump in the event of an accident. The switch senses the impact and opens, cutting power. These switches can be hard to locate. My truck's ('86) inertia switch is fastened to the floor high up near the heater box on passenger side just hidden by the carpet. I think if the switch is open, the red button will be popped up out of the recess it normally sits down in. Some models, look behind r side kick panel for the switch. An easy way to check if the normally closed inertia switch is open is to unplug the four wire plug at the fuel cutoff relay (assuming your F350 has a 7.5L engine). The pump power/cutoff relay is easy to find and access. I should be bolted high on the fire wall near the drivers side fender. The yellow wire should have power if the inertia switch is closed as it should be. If no power, locate the inertia switch and reset it by pushing the big, red button.

The inertia switch is powered by a fusible link.