How to plumb gas tank vent

I’ve got an old bronco that I’m putting back together and we are going to install a fitech unit after I break the motor in with the carb. 

So we went the easy route and bought a large efi tank with an in-tank pump. 

I had planned on just running the tank vent up inside the rear fender with a little filter on it and call it a day but I got to thinking about the smell and environmental issue with an open vent and did a little research. 

The bronco came with (and mine still has) what appears to be a fuel separator mounted up high inside the truck but covered behind a cover.   As far as I can tell, the two original tanks would have vented to this, which is higher than the tanks so no fuel that would have made it out of the tank would have got trapped in the line (like in a p-trap). 

So I thought I would run the vent to this separator (if that really is what it is), run from there to a charcoal canister that has an in and an out and run a line to the air cleaner to pull the fumes into the motor. 

Related, I believe the gas caps on the truck are vented but not sure  

With this setup, the motor should put a small vacuum on the line, drawing air and vapors from gas cap-tank-separator-charcoal canister-air cleaner.   

And if the tank is too full and there is no air path from the vent to the filler neck, wouldn’t the vacuum be too small to pull fuel through the lines up to the separator?

I know some (all?) canisters have vents...  necessary?  Same with valves on the canister or elsewhere in the system.... necessary??

Sounds good to me.  I have the same problem. I plan on getting a charcoal canister and install it on my project car. It came with a  vent to the air cleaner but I can't remember if it had a charcoal canister stock (1974)?

In reply to jfryjfry :

Coal is definitely the best idea.
I don't think there needs to be a hole.

Easy button... just get a modern "sealed" gas cap.  They aren't really sealed, actually.

The way they work is that they begin to vent at a very low PSI.  When its hot, it vents a bit.  Then when it's cool, there is a one-way valve that allows air in so you don't collapse the tank.  The purpose is to limit, not eliminate vapors from getting to the atmosphere.  The charcoal canister only works during engine operation, not really as an effective vent.

It was motivated to eliminate potential odors as well as be a little more environmentally friendly.  

The new sealed gas cap sounds promising.  

Hoping to find a discarded canister I can at least try out. 

I know someone here has got to have a few they aren’t using!

I went with a sealed cap on my 66 Bonneville.  I was at a junkyard and there was a gas tank sitting in the mud.  Looked like maybe a 3rd gen F-body tank.  I just snagged the filler neck and stabbed it on the filler hose of my Bonneville with the cap.  I think the yard charged me $5.

jfryjfry said:

Hoping to find a discarded canister I can at least try out. 

I know someone here has got to have a few they aren’t using!

Actually, I'm looking for one myself :)