external fuel pump questions for4.0L engine swap to diff. make of vehicle

[piedrarock]

I was looking through past threads re. extenal fuel pumps , and found enough info to start this thread and ask more in depth questions to the points I read earlier .
I see that in some applications a fuel system will run two fuel pumps , a high and low pressure one, would the low be in tank and high outside .
would there be a fuel regulator after high p. fuel pump or is that factory pump dialed in already to specific psi ?
in my case having old style gas tank with fuel pump at engine drawing fuel threw a line at bottom of tank, would i be best to go with high pressure external pump , into biggest type cannister filter or two i can find(for maintaining volume in line in case of big hill ) , then a fuel regulator to dial in sufficient pressure to engine or swap order of cannister(s) , reg.? rubber line from tank to h.p. pump , metal afterwards and where can i get back to rubber lines nearing engine?
next question , fuel return line, does a91 4.0 l engine have this plumbed in from factory ?
Anything else of major importance that Ive overlooked ?
As always , thanks in advance for your input , This forum has such diversity, anything and everything is just a search away .

 

[RonD]

The 1991 4.0l EFI computer needs 30-40psi pressure at the engine end, at the injectors
Fuel rail will have an IN line on drivers side of fuel rail toward the back
It will have an FPR(fuel pressure regulator) on the passenger side towards the front, this has the OUT line, the return line back to tank, it has 0psi, just flow
(FPR also needs a vacuum hose attached, this stabilizes fuel pressure as engine load changes)

The IN line should be re-enforced "rubber" that is rated for 70-100psi, at least
I would use same for Return just because its safer

You can get universal electric in tank pumps with SENDER for gas gauge
For 4.0l V6 40-60GPH(gallons per hour) would be fine

 

[piedrarock]

im leaning towards external system , so i can use original tank , dont have to cut or enter tank to mount internl . plum xternal and its neccesities towards engine and hopefully maintain fac . fuel gauge and only one stub for exiting of gas and one vent stub that is attached near top on gas tank filler nozzle

 

[RonD]

Shouldn't be a problem using external high pressure pump, you should have a reservoir between tank and pump
Canister type filters can act as a reservoir, this holds "Prime" in case gas in tank gets too low

Problem is you MUST have a Return line, even with external high pressure pump
So you might as well use the current FPR with return line setup on the engine now

With carbs you could just have a pump
With EFI and the higher pressure you will run into problems with an FPR without a return line

Computer doesn't have a "fuel pressure sensor", it needs to have a consistent pressure within 5-8psi of what it was programmed for, 35psi in this case
The problem is at idle fuel demand is low, but when accelerating or cruising above 50mph fuel demand is high
So without consistent pressure computer can't keep the air/fuel mix correct, so lean/rich, hesitation, and maybe stalling, if pressure varies too much

Only way to maintain that is with FPR with return line, even external pump would require that
Look around, maybe someone has found a solution for this

Even "returnless systems" have a return line, lol, its just on the fuel filter with FPR in the gas tank

 

[piedrarock]

That make perfect sense , to have larger cannister filter just at outlet of stock vw gas tank, then hi. pr. pump (close to ford fac. specs of 30 -40m lbs)into fuel regulator, with regards to the fuel return line that WILL BE returned to tank , i seem to remember a small vent line up top of fuel fill stem , maybe i could connect a" Y" type fitting to this , with the y down part of fitting being the one the return line is attached to , and the other straighter part continuing upward to maintain factory venting system
is this doable ?

 

[RonD]

Yes, you could put a "T" in a vent hose, or in a Filler hose, for the Return, its 0 pressure just flow, just make sure it can run Downhill back into the tank, lol