EFI fuel line plumbing question

[broncbusted]

Hello I have searched and read threads on this and I know its a controversial subject. People have had success using all combinations of things. I have a 76 and am installing the 93 Mustang EFI system, 2 original fuel tanks, 6 port electric selector switch, external high pressure fuel pump, filters on each tank feed to selector switch, and filter on pump outlet to fuel rail.
I am confident on the installation on all of the above its just a matter of location and making it a neat install!
My question is the return line from the engine? I am planning on installing a Tee in the rear tank vent line (5/8" line from tank to fuel cap). I can do this easily on the rear tank but the aux tank is not so easy. I am thinking about taking the two return line connections on the selector switch and connecting them to the rear tank only.
Does anyone see a problem with doing that?

Thanks

 

[gddyap]

You'll probably drain the aux tank pretty fast when you switch over to it. The fuel pressure regulator adjusts the pressure based on engine vacuum by bleeding fuel to the return. So fuel will get pumped from the aux tank to the fuel rails and some will go to the injectors and some will return to the main tank. You'll see the fuel gauge drop faster than usual. If you switch over to the main, you'll see it have fuel in it again. I don't know how quickly that will happen though.

 

[POPPAWS BRONCO]

Some folks (not me) have just pumped the fuel from the aux to the main tank with a switch when wanting to keep both tanks but go EFI. I'm undecided if I will do this since I replaced my rear tank with a tank bigger than the two tanks combined from the factory. I do like the thought of the extra fuel just don't see a need anymore in my case.


Hey!!! Let me hold a dollar I'm in the middle of a restore here!

 

[ezbngreen]

I have a 2 tanks with a transfer pump in mine. It's nice to have. You just need to watch the fuel level. It's easy to forget the transfer pump is on and dump fuel on the ground.

 

[garberz]

.........My question is the return line from the engine? I am planning on installing a Tee in the rear tank vent line (5/8" line from tank to fuel cap). I can do this easily on the rear tank but the aux tank is not so easy. I am thinking about taking the two return line connections on the selector switch and connecting them to the rear tank only.
Does anyone see a problem with doing that?

Thanks

The problem I see would be, if you filled up both tanks and started off using the Aux. tank first, the return fuel would be overflowing your main tank. I'm sure that scenario would happen eventually. Using the Aux tank as a transfer tank is what most do. It keeps the plumbing and use, very simple.

Mark

 

[73azbronco]

I think that 6 port valve is what you need right? There 2 lines from the rear, 2 from the aux, and 2 to motor. One is feed one is return to each location right? Switch is off a mid 80's/90's F150 or so? I was going to use that switch/valve but decided I didnt like the spider web of hoses that would result and just went with a bigger main tank. The oither issue was different sized hoses to each port, I was not going to sit and figure out how many different hoses and adapters that would need.

If you really want two tanks, I also recommend just using a pump to transfer fuel from aux to main. Just be sure there is enough space before you hit transfer.

 

[broncbusted]

Thanks for all the knowledge!!!

Thanks for the replies and all make sense!! I did not think about overflow! I was just looking for an easy way to plumb. I should have known it was too easy!!! I guess I have to make a decision on using the aux tank! I am kinda liking the transfer from aux to main tank idea. It's just more cash outlay but I am used to that!!!!!! Money can't be a concern when trying to restore the Bronco!!!
Hey thanks for all the good info, asking a question here saves time and money!!!!

Hey Pappaws , I will be glad to let you hold a dollar but it won't go very far on a Bronco restoration!!!!!!

Thanks again,
Paul

 

[Steve83]

People have had success using all combinations of things.

Yes, there are usually a few "right" ways to do anything, depending on exactly how you want YOUR truck to work. But there are a LOT MORE wrong ways.

...filters on each tank feed to selector switch, and filter on pump outlet to fuel rail.

That's overkill, unless you think there's some way for the fuel to become contaminated at the selector valve.

...easily on the rear tank but the aux tank is not so easy.

On the '75 I converted to EFI, each tank had several small nipples near the filler. I used one of them on each tank for return fuel.

I am thinking about taking the two return line connections on the selector switch and connecting them to the rear tank only.
Does anyone see a problem with doing that?

A BIG ONE.

Suppose you (or someone else who's driving it for whatever reason) fill up both tanks, and then drive on the front tank. Its unused fuel will go to the full rear tank, overfilling it until gasoline spills out. That's expensive, illegal, and dangerous.

Any time you pump fuel from one tank to another, you MUST provide a way for any overflow to return to the tank being pumped out. But it's easier to just return the fuel to the tank it came from in the first place. That's why the selector valve has 6 ports.

 

[broncbusted]

Thanks Steve83

Hey Steve, Dang another great point!!!! I am still considering what to do! Dang It!
Ok Steve question? I do have those vent ports on my tanks also. I thought that would be perfect and easy to connect to on both tanks!!!! Yeah but then I began researching this forum and found posts saying those are for the fuel evaporative system and they are restricted inside the tank and not good for return lines? People have had problems with fuel vapors inside garages from not connecting these to a system to burn these vapors? Did you have any problems when you plumbed your 75?

Thanks
Paul

 

[73azbronco]

PLus on dual tanks there is an in cab as best I can describe it "a web of vent lines behind the driver side wall" container. Cannot imagine what they were thinking when they made that piece of plastic thing.

 

[Steve83]

...those are for the fuel evaporative system and they are restricted inside the tank...

I don't recall any problem, but a drill bit that fits into the nipple would remove any restriction.

People have had problems with fuel vapors inside garages from not connecting these...

Then don't "not connect" them; connect them to the fuel return lines, and no vapor will escape.

Did you have any problems...?

I modernized it in many ways, including the evaporative system. I put the vapor/rollover valve from the '88 donor truck into the eB tank, and routed the vapor lines to the '88 charcoal canister in the engine bay. So it never had vapor problems.

(BTW It was Frank's truck - not mine. I just built it for him back then, and sold it for him a few years ago.)