I got some questions regarding the conversion we have coming up. My brother is the mechanic behind it, basically I'm the labor - but it's my truck .

I woke up this am thinking about this problem, and don't want to wait the 7 hrs it'll take for him to get up (night shift) to get the answer. Besides, then I can TELL him how it has to be done rather than listen!

Bear with me, I'm pretty detailed (wordy) .

OK, we are converting a 1978 F150 from a carb'd 460 to a 460 MPI, and we have an aftermarket harness and computer to do it.

Right now I have a small electric pump I'm using (universal, low pressure) from a botched throttle body conversion we tried (turned out to not be emission compliant so we returned instead of chancing), and of course, dual tanks. I've already bought another in-line pump to replace that one.

Here's the issue, at least in my mind -
That return fuel line (which is not present in the current system) - doesnt that have to run to the tank that's being pumped from? Aren't we missing something to tell it which tank to go to?

How would that work - do I need another tank selector so that the return line runs back to it, and then it goes to whatever tank is "on" at that time (run jumper wires from existing tank selector so they always sync)?


Then another potential problem occurred to me - my gas tanks aren't designed for a return line. Do they have to be? How are we going to plumb a return line into the existing tanks, or will it just go into the rubber necks of the fill hose?


Hopefully someone with the know-how will be able to answer these issues, and throw out some more problems we also will need to work around - and then when my brother wakes up I can slap him around for not thinking of this
.

 

If you can use 89 style sending units, they will have the needed return line fitting and the low pressure pumps to feed the on frame high pressure pump. You would also need the selector valve from an 89 to switch tanks.
Or, if they fit your tanks, you could use 2 93 type sending units which have a high pressure pump in each tank and a built in check valve in the return lines. I prefer the 89 style myself.

 

Can I get away without an in tank pump?

I already have a selector - what is the reason I would need one from an 89?

 

86-91 are the same. They have the 6 lines needed. Most high pressure frame mounted pumps don't suck well. This is why they are fed by the low pressure in-tank pumps.