......recently FULLY re-wired a '86 with new harness(post -fire rebuild)--I've got EVERYTHING working,cept I got stumped about the fuel pump wiring.The donor unit was similar year,and accessories,with dual tanks,but I'm not going to say how long it took me to realize that only a 460 uses a tank/electric pump ,rather than mechanical.------In any case,for now,I've got the forward pump hooked into the tank switcher,since it's live only when the fuel switch is in 'fwd' position,,,,,,,and have the rear pump powered by an accessory wire which is live only in 'run' on the ignition,and have a separate kill switch wired in.
---is the above retro-wiring safe/efficient?
-----should/how would I develop a proper setup to power the fuel pumps,otherwise??........thanks!

 

From what I understand the fuel pump or pumps have power running to them but the actual switching is completed through the computer by **Grounding** the circuit

 

each of my tanks has 4 wires coming off-2 being grounds,one being guage,and of course the 4th is power to the pump....but I'm wiring into a harness that had a mechanical pump on the engine,and will have to develop the best way to power the pumps.--the harness I'm useng definetly used + to activate the switcher.

 

The haynes manual in the store has this wiring circuit in it. It's called "hot fuel handling".

They way you have it wired is not the best, but people do it on street rods all the time. What you are missing is two safety shut off circuits.

The factory system used a fuel pump relay. This relay was controlled by a oil pressure switch. If the engine dies for some reason, the fuel pumps cut off automatically.

The other safety device was the inertia switch. This should still be in your truck somewhere, if it didn't get burnt up. I think sometimes it's mounted behind the pass side kick panel. This switch is placed in direct line with the power wire to the fuel pump relay contact. It has a pendulum that if it is jarred severely, the pendulum will swing and disconnect the power to the pumps.

One scenario I can think of is your in a bad accident, your knocked out, or so shaken up that you don't turn the pumps off. As a result of the accident, the fuel system is leaking somewhere. The pumps keep running, and the fuel is running all over the accident scene.

Ford and the other car makers do all this stuff so they won't get sued. You don't have to, but it's up to you.

By the way, originally the fuel pump power was selected between the two pumps in your truck by the dash switch. The other side of the switch fed a motorized valve. The motorized valve switched the sending units for the guage. But since you don't have any of that wiring now, you will have to invent your own method like you have done, or re-wire a little bit.

 

franklin2--tanks lots!--I owe you a beer fersure!!