EFI - Fuel Return w/Main & Aux Tanks

[Jeff10]

Hey Everyone,

I'm working through options for upgrading my fuel systems.

I am really leaning toward propane; but, I want to make sure I consider all the options, and include all the costs.

If I go with EFI (either something like MDS Atomic throttle body or parts for a multi-port from a production 302) I understand that a return line is required. (I guess it is debatable regarding the Atomic system; but, I read yesterday that if high temps are expected, a return is required... so a return would be required for me.)

Our '71 has a main and auxiliary tank. If I were to convert to EFI, how would that work with the return? I'm thinking that a selector valve will be required at each tank for both the supply and the return so that the return is always going back to the tank from which the fuel is drawn. Am I looking at that correctly?

Or do folks running EFI tend to run just the main tank?

I've also read a little about the aftermarket tanks that have provisions for return lines. And, I've read about guys that tie into vent lines or filler tubes. What is the right (and safest) way to do that?

Any information will be appreciated.

Thanks

Jeff

 

[Viperwolf1]

Most people just prefer to run off one tank. Maybe use the aux tank as a transfer tank. I run off both my tanks. I have a low pressure pump near each tank. They feed to a 6 port valve (switches supply and return). Then accumulator and high pressure pump. Its a little complicated but I haven't had any problems since I got the LP pump sizing figured out. I added a return port to the aux tank sender. Same could be done easily to a stock main sender. I have a NWMP main tank so I ran the return to the drain plug hole. 6 port valve also switches LP pump power and senders so I just use the stock dash switch to control it.

 

[suckerpunched]

I was going to run the two stock tanks but I think at this point I am going to buy a large capacity EFI ready tank and be done with it.
My plan was to use a frame mounted walbro pump, I used 1 on an efi conversion i did on my brothers jeep, it was about $110 from sumit and has worked perfectly. Actually I was going to use 1 for each tank, and 1 fuel pump relay for each pump selected by a toggle switch in the stock location. For the return. I used to have a forklift with an electric fuel shut off. It was a valve with 5/16 in and out and a wire that when energized, opened the valve. without 12v to the wire, the valve was closed. I was going to use 1 of these valves for each tank, jumped off the 12v lead to each pump. So that when one of the pumps was running, the valve would open and return fuel to tank that pump was pulling from. I figured if a fuel pump did fail, it would still run off the other tank.
I am pretty sure it would work fine. but by the time you buy 2 pumps, valves, relays, extra fuel line and wiring. and probably needing to replace both sending units. For not much more, I could buy an EFI tank thats ready to go.

 

[Jeff10]

Viperwolf1 and suckerpunched,

Thanks for the detailed info.

Viperwolf1... that must be one heck of a setup! Maybe you should sell a kit.

After doing some searching it appears that 23 gallon replacement tanks are sold which are advertised as EFI compatible. I don't see references to any of the auxiliary tanks being sold by Bronco vendors as being EFI compatible. Is this the case?

When I was younger I thought KISS (Keep It Simple, Stupid) was just an excuse to take the easy way out. It's now a principle I follow. This may be a good time to follow that principle. We'll see.

Thanks for your input.

Jeff

 

[tasker]

will be running an aux tank as a transfer for for my build. As stated, will run a low pressure pump to fill the main tank back up....Broncokak has run this setup for quite some time with no problems....as long as he gets his pump back after being loaned out ;D (inside joke from the Round Up)

 

[Viperwolf1]

After doing some searching it appears that 23 gallon replacement tanks are sold which are advertised as EFI compatible. I don't see references to any of the auxiliary tanks being sold by Bronco vendors as being EFI compatible. Is this the case?

EFI compatible could have different meanings to different manufacturers. Ideally it would contain 1) baffling around the fuel pickup, 2) internal fuel pump capability, and 3) an independant fuel return port.

Baffling is important to prevent fuel pressure loss if the fuel pickup is momentarily exposed to air in high angle situations. Carb's have there own reservoir so this doesn't affect them as much. You can do without the baffling by using an accumulator as I did.

Internal pumps are quieter, run cooler and are generally make for a cleaner, easier install. Pump maintenance is easier with external pumps.

An independant return port should be used. Vent ports in stock tanks have small orifices inside to actually prevent liquid fuel from flowing through them. They also already have a function to perform and it doesn't involve fuel flowing through them. Ideally you want the return port to run to the bottom of the tank to reduce noise and air bubbles in the tank.

 

[airbur]

will be running an aux tank as a transfer for for my build. As stated, will run a low pressure pump to fill the main tank back up....Broncokak has run this setup for quite some time with no problems....as long as he gets his pump back after being loaned out ;D (inside joke from the Round Up)

That's how I set mine up. Aux line to pump and into return feed to main tank. Also hooked it up to OEM tank selector.

 

[jmhend]

Ok in the simple terms of the question does anyone have this sketched out on a bar napkin?

 

[airbur]

http://www.bcbroncos.com/EFI plumbing 1 tank and external pump with water mark.pdf

http://www.bcbroncos.com/fuel system pluming with water mark.pdf

 

[MyOriginal66]

I'm running the 23gal BC Bronco EFI tank w/built in pump. Im also running a aux tank for "spare" fuel. I ran a tee and low pressure pump on my return line to the main tank. Activate the low pressure pump and it fills the main tank. BC broncos can set you up with everything you need.

Whats great is you can run the aux tank dry most of the time, then if you have a long trip planned fill it up so it's there if you need it.

 

[jmhend]

Awesome...thanks guys. I am in the planning stage now thanks to some newly acquired efi goodies from Tasker....

 

[Kegger]

Iam running early school efi tank 23gal just a sending unit, line in /out @ the top piped inside low/draw/ fill , 6 an return 3/8 to 1/2" to inline filter back to 6an again walbro 190 just up graded to 225 for the stroker its fine. preasures the tank a little . 40 psi@ rail. stock 95 fuel rail. my tank been in there for 7 years + - ken

 

[landshark99]

iam also running a 23 gallon EFI tank with the stock aux tank transferring into the EFI return line.

I put a filter and low pressure pump then a one way valve that dumps into the low pressure return line going to the main tank. I wired it up to turn on the pump and fuel gauge to the aux when you flip the fuel dash gauge switch. Easy.

 

[airbur]

Some good info here..

http://www.alpineclassicbroncos.com/viewtopic.php?t=120