Return Line for EFI Conversion

[VasiliBrown]

Hey everyone. I have an 85 mustang that was a 4 cylinder car, previous owner swapped in a 92 5.0. Currently carbureted and going to swap to efi using a Fitech kit. Trying to think of the easiest way to run a return line, hopefully avoid dropping the tank. Has anyone used the vent on top that goes to the charcoal canister? Was thinking about running the return to there. Also thought about taking out the sending unit and brazing a fitting onto there. Current sending unit does not have a return line on it

Third option would be could I just replace with this sending unit? Looks like it already has a return
https://www.gastankdepot.com/sufm-07-1984-85-ford-mustang.html

[emerygt350]

Hard to believe the 4 wasn't fuel injected, but I guess my old 86 escort had a carb on it too. I wouldn't mess with the tank vent.

[richpet]

Guess there were some differences. My '81 Granada originally had a 4 cyl and it had a return line.
Is it possible you had one and the PO bypassed it? Or did the Mustang not have one at all?

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[VasiliBrown]

I have updated the post with a picture of the sending unit just in case I'm missing that there's a return line haha

[at_the_junkyard]

FWIW when I did my EFI conversion I went with an EFI tank with two opening. One for the in-tank fuel pump (which incorporates a return connection) and a separate one for the fuel level sender. I ran another fuel return line all the way back from engine compartment.

More work and money to install but I think it is the way to go in the end etc...although in my case I was already upgrading to the larger tank (from my original 80 small tank). Many different ways to do it though.

[at_the_junkyard]

Forgot to add that if you wanted to run an external fuel pump you could just replace that fuel pickup/sending unit with a replacement (non-efi) that has the return line connection also. I know LMR and probably others sell them.

Also, I agree that you should not mess with the vent line. I believe it has a check valve at the tank that allows vapors to exit while filling and, in the case of a rollover, prevent liquid fuel from spilling out if you are upside down.

[grtskydog]

I know this is a couple of weeks old, but here goes my 2 pennies. I've been running the FiTech on my combo for several years (I have an early production GoStreet 600) on my formerly-carbed '85. Here's what I'd recommend for the least headache and best reliability: Pick up an EFI tank and use an in-tank pump. It's almost always better to "push" fuel rather than try to pull it with EFI pressures. Fox cars are great since we have this option. Most FiTech'ers have to mod their tanks, or buy expensive special-built EFI tanks, to eliminate the in-line pump/"fuel control center" fiasco...we can just go to the Pick n Pull or AutoZone and grab our favorite Walbro to go with. There is an elegant 3-in-one solution to plumbing the FiTech...a 2001 LS Corvette fuel filter (WIX 33737 or similar) It serves as a filter, regulator, and return. It is a 58psi regulator, so it only works for certain FiTech models, not the 45 psi ones. My LS filter is mounted near the tank, so I only run 1 line forward to the engine bay, and the return runs about 18" back. You can get a block-off piece for the stock regulator on the throttle body to eliminate it. The kicker is the LS filter is 3/8" but you can adapt that or run bigger lines. Either way, dropping the tank isn't a big deal (if it's pretty empty ). Replacing it with an EFI version would solve a lot of current and future issues.

IMO, anyone with a Fox and any aftermarket EFI system should just run a stock-type 86+ tank. Don't look that gift-horse in the mouth.

[richpet]

To share a different view:
Mounting an electric pump near the tank to push fuel to the engine bay got the FiTech is easy. No tank to drop/replace
I mounted a low pressure electric pump on the spare tire well. Easy
The FiTech ForceFuel unit with HP pump takes it from there, mounted in the engine bay. Easy.

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[gmatt]

I've got the FiTech on my 80 Fairmont. I had the original tank modified with a 3/8 return (-6)AN fitting and a 1/2 (- pick up. I ran all new steel supply and return lines. Frame mounted high pressure pump right next to the tank. I think I paid $150 for the modifications. Works great, but the pump is kind of loud.

[emerygt350]

That is basically what Ford did with early injection. I have 2 pumps, one in the tank and one a couple feet aft of the transmission.

[grtskydog]

That is basically what Ford did with early injection. I have 2 pumps, one in the tank and one a couple feet aft of the transmission.

Yep, I think the CFI cars had a low pressure pump in-tank to move it out and a HP pump in-line to push it. I had a CFI GT way back in college and seem to remember that setup. I remember when the FiTech came out and all the issues were with the FCC, trying to adapt the older carbed cars to TBI. I decided to avoid all that since the “Foxen” are ready made for in-tank setups.

I stand by my recommendation.

richpet, is the ForceFuel something more recent? I haven’t heard of it. Maybe their answer to the FCC issues?

[emerygt350]

Yeah, works but sadly just means two pumps to fail...

[richpet]

The Force Fuel is a small (1/2 gal) tank with a submerged HP pump to feed the actual FiTech throttle body. The small electric carb pump I mounted out back keeps it full, the FF feeds the motor.
It has a fuel pressure gauge mounted in it. The unit can be mounted anywhere essentially. I mounted mine where the windshield washer tank used to be.

As for actual pump failure, I have a spare electric one anyway (under $50) and the one in the FF unit is easy to get to. Pumps themselves have rarely failed on me so not too worried.

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[massacre]

That force fuel system is very interesting. Almost like a remote sump. Never would have thought of that.

[richpet]

I will post a pic when I get home.
Technically I am supposed to run a 3/8 return, but I am using the factory 1/4 line.
This is all still on topic I think. Has to do with a return line for efi.
For me it was super easy. Holley pump out back, unit under the hood.

Three lines: fuel in. Return. HP to unit.
One power wire one ground.

Mine all came as the Easy Street kit for up to 600HP.

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[grtskydog]

Looks like they redesigned the FCC. Same concept. I’m guessing it is a more reliable system than the original. I just remember a lot of complaints when FiTech first came out.

Here’s what I was talking about. 58 psi filter/regulator. Wish they made the -AN one when I did my fuel system.




Or this one….