EFI BC Broncos Fuel Tank Venting Question

[canzelc]

I have an EFI 23 gallon fuel tank from BC Broncos installed in my '73. When I installed the tank, I installed a piece of fuel line on the vent nipple, zip tied it to the filler hose and left it open on top at the top of the filler neck.

The problem is that fuel will leak out of the top of the vent line when the tank is full. The '73 has the fuel vapor seperator plastic bottle behind the drivers side door post. There are two lines that ran from this plastic bottle to the original rear tank. My question is can I run the vent from the EFI tank to one of these lines and plug the other? If so which one?

 

[pbwcr]

I have an EFI 23 gallon fuel tank from BC Broncos installed in my '73. When I installed the tank, I installed a piece of fuel line on the vent nipple, zip tied it to the filler hose and left it open on top at the top of the filler neck.

The problem is that fuel will leak out of the top of the vent line when the tank is full. The '73 has the fuel vapor seperator plastic bottle behind the drivers side door post. There are two lines that ran from this plastic bottle to the original rear tank. My question is can I run the vent from the EFI tank to one of these lines and plug the other? If so which one?

==
Copy the stock vent setup. I have a 72 and the vent goes to plastic tank line then to charcoal canister.

 

[canzelc]

I guess my question is about the stock tank venting. Why did the stock tank have two vents? Do they serve the same function? Can I use either or plumb them together and connect them to the vent in the new tank?

 

[pbwcr]

I guess my question is about the stock tank venting. Why did the stock tank have two vents? Do they serve the same function? Can I use either or plumb them together and connect them to the vent in the new tank?

= ===
My 72 plastic jug one vent for the main and one for the aux tank. When I got rid of the aux I just capped the plastic jug vent that went to the aux tank. Your 73 may be different?

To be sure maybe someone has the fuel system schematic. I have never seen one. So I don't know if my system was stock when I got it.

 

[canzelc]

I did a little reading on a few old threads and from what I gather the fuel vapor separator has four connections; main tank vent, aux tank vent, line to charcoal canister and liqiud fuel return line (plumbed to the rear tank).

My plan is to plug the aux vent because I only have the main EFI tank. Install a T on the EFI tank vent mounted vertically and run the vent out of the top outlet and the liquid fuel return into the bottom inlet. When I install an air box I can plumb the outlet from the charcoal canister in to the air box ahead of the MAF and the system should work like it did originally.

Does this sound like a solid plan? If so the only thing I need is to know how to identify the vent line and the liquid fuel return line.

 

[DirtDonk]

Depends on the vintage of the tank perhaps, as I believe they've gone through at least one change in port orientation.
The current one at least has the fuel feed and return lines in front of the main fill port, and are both threaded for -6 AN fittings.
The next one behind the large fill hole is the fill-vent.
The rearmost fitting is the vent.

I would think the best method here would be to use a "T" or a "Y" in the vent line. One is for venting to the plastic condensing tank, the other for the returning liquid.
You could certainly use the fuel return line, but the disparity in sizes might make it less desirable?

Paul

 

[canzelc]

You described my tank, it has all of the fittings you described in the order you stated.

Since the new tank does not come with a second vent (liquid gasoline return line) like the stock tank did and I do not want to interrupt the EFI fuel return line, my idea was to mount a vertically postitioned T on the single 5/16th vent on the EFI tank. The T fitting could be compression on the tank side with barbed fittings pointed up and down, vapor line on top and fuel return on bottom.

I think that these two lines should remain seperate for as long as possible. Only problem is I do not know how to identify which of the existing lines coming out of the vapor separator is which. Does anybody know which one is which?

 

[LA75]

I just put EFI in my 75. If yours is like mine, you should have 2 metal lines that the stock dual fuel vents plumbed into. I made a T from brass fittings and connected the single vent line from the 23 gal tank to the T and then attached to each hard line. Been running now for a month without any problems. I wanted to utilize the charcoal tank and all the vent lines I re-plumbed prior to the EFI and 23 gal install. ps: no fuel smell either.

 

[canzelc]

That sounds exactly like what I am thinking about doing. Can you post up or email me some pics?

I will pm you my email address.

 

[DirtDonk]

Hey canzelc, check the forums here as there was a post just a couple of weeks ago where someone of the regulars had a diagram (photo with circles and arrows and numbers!) showing which one was which.
Sorry I don't have a link, but it was very recently.

Paul

 

[canzelc]

That sounds helpful. I learned a lot of good information reading through a couple of different threads last night. I will search again using some different terms. If anybody has the link that would be fantastic...save me some time.

 

[canzelc]

I searched and could not find anything with labels for the stock tank. The stock tank has two ports towards the front of the tank (vent and return). Does anyone know which of these is the vent and which one is the return line?

 

[LA75]

Canzelc, I will take some pics tonight.

 

[canzelc]

Any help would be greatly appreciated, thanks.

 

[canzelc]

So here is what I ended up with. I made a simple manifold out of a 5/16th brass compression T and some 5/16s copper tubing. Then I used 5/16s fuel line and connected the two lines from the vapor separator to the single vent on the tank. I would have liked to have known which line was the vent and which was the return but the limited room above the filler fuel filler did not allow me to slope the lines the way I wanted to. I think it will work the way it is though. I will recheck the connections and put a full tank of gas in it after work today and see how it works.

 

[LA75]

Sorry, I got home late last night and didn't take the pics. But that looks pretty much what I did. Except I used 90 degree fittings instead of the tubing. And I strapped mine to the frame rail to prevent all the movement of the lines.

 

[70Sport]

How is this working out?

I have an older BC tank that I am wanting to hook back up to the factory vent system.

 

[canzelc]

It is working ok. The main problem I have with it is when I fill up the tank I get a lot of liquid fuel coming out of the vent line and a decent smell of gas inside the bronco which is coming from the area where the stock vapor separator is located.

I am not sure why I am getting so much liquid fuel out of the vent line at fill up and with a full tank. I would like to replace the stock vapor separator with a unit that I can mount outside of the cab. Has any one ever done this and if so what model vapor separator did you use?

Maybe something like this:
http://www.ebay.com/itm/Moroso-85474-Universal-Air-Oil-Separator-/302135143107

 

[DirtDonk]

...I am not sure why I am getting so much liquid fuel out of the vent line at fill up and with a full tank.

If you're speaking of the separator tank, it might not be liquid at all, but just the fuel vapors making their way up there. You'd still smell them pretty good if your seam has split. Which is what it sounds like has happened.
Very common on the old tanks.

If you meant the big fill-vent hose into the filler neck though, not sure why you'd be having trouble with this type of tank. Very common on the old stock tanks, but not so much on the replacements.

I would like to replace the stock vapor separator with a unit that I can mount outside of the cab. Has any one ever done this and if so what model vapor separator did you use?

Just eighty-six the old separator and use a more modern style charcoal canister mounted up higher than the tank. Same function, fewer parts. And none in the cabin to smell up the joint!

Junkyard item, or Summit or even your local auto parts store will be able to get them. It's the standard item from the late seventies (and what Broncos came with starting sometime in '76) and you can mount it where Ford put them, up on the passenger side firewall. Or down under the passenger side wheel well. Believe it or not, you can get it almost as high there in the well as you can on the wall.

As long as it's higher than the tank, you'll be good to go as long as you're not truly pushing liquid up the lines. If so, you'll still have to figure out why.

Paul

 

[canzelc]

LIquid fuel is definately coming out of the small vent not the fill vent. So I need to find a new vapor seperator so I do not flood out the charcoal canister with fuel.

What do you think of using an air/oil seperator for this like the one posted above?