Question about fuel cell vent line

Installed a fuel cell in my trunk on my 67 Coronet. All is good but I smell gas. It is vented but at this time it is just a straight hose out of the tank through the trunk floor. I am going to get a longer hose so I can loop it but also wondering about a roll over valve and some sort of an attachable charcoal canister? to help stop the fumes smell. Is there such a piece that would work as both a one way valve and fume stopper? Thanks.

The factory guys have spent a lot of time working on that issue over the last 40 years so you might just copy what they do. The vent doesn't need to be very large so that is the most common mistake that people make. Adding a canister might be the easiest first step. One thing you have to watch out for with a fuel cell is that typically they are not designed for street use so they don't have any place for the vapor. Most fuel cells have a flat top so if you fill it to the top there is no room for the vapor. There needs to be an expansion tank of some sort attached to the fuel cell if you're going to drive it on the street.

My garage stinks of fuel in the summer from non-evap controlled cars venting gasoline fumes. It's at it's worst after I've driven the car on a hot day and then park it in the garage.

The vent line needs to be large enough to allow the same volume of air to enter the tank as the volume of fuel that leaves the tank and goes to the engine (minus whatever is returned if you have a fuel return system). Otherwise you will have fuel delivery problems.

What I did to resolve the issue on my fuel cell was to run the vent line to a tee fitting. On one side of the tee fitting is a check valve that lets air into the tank to compensate for the volume of the fuel that is pumped out of the tank when running but not let vapors out. On the other side of the tee is an adjustable pressure relief valve so that the vapor has to build up a little pressure before it can be released. It’s set at a pretty low pressure setting so the fuel cell doesn’t become much of an expansion tank, which it’s not designed to be. After doing that, no more gas smell in my garage.

where did you "exhaust" the pressure side of the T fitting to ?
TIA.

It's just vented below the fuel cell. On the outside of the car, obviously.

So the problem really is, how are gas fumes getting to the drivers nose?
Is the problem when driving, or sitting still or both?
Seems figuring this detail out would help get the vent located into a moving air stream that does not recirculate fumes back to the car when in motion, which so much of the air does at the rear,

You can do the junkyard crawl and grab a canister, vent valve, and purge solenoid from an older Ram or Caravan. The vent valve is the one way valve (it will have a filter as well). The fumes will accumulate in the canister. If you hook up the purge solenoid, one line goes to the canister and the other to engine vacuum. The solenoid is 12 volt, so hook it to a switch. When you start the car, flip the switch and purge the canister for a few minutes to clear it of the previously stored vapor.

This sounds interesting. I just ran an aluminum fuel line vertically a few inches, made a u-turn and back out through the floor of the car. No gas smell in the garage that I've noticed.
But I like your idea better. What parts did you use for the check valve and pressure relief?

The bigger the electric fuel pump, the bigger the vent needs to be from what I've seen and a customer of mine Shane Studly races a wagon w/a stock gas tank and an elec. pump and it crushed the brass float we USED to run from not enuff pressure escape/ventilation. He vented the fill neck, and problem solved and it actually filled his crank case full of gas on the way home from a race before he vented it. I plugged mine once and the pressure went past my pump and straight into my carb.....

Mine was originally ran this way, down to a charcoal filter. The fumes were overpowering when I walked into my garage. After changing to the PRV and check valve setup, no more fumes.

The pressure relief valve is very similar to this one, but I think the range on mine is 0-15 or 20 PSI. It's currently set for somewhere between 1 & 2 PSI.
https://www.ebay.com/itm/0-100-PSI-Brass-CR-Series-Adjustable-Air-Pressure-Relief-Valve-Control-Devices/291696721009?_trkparms=aid%3D1110009%26algo%3DSPLICE.COMPLISTINGS%26ao%3D1%26asc%3D20200220094952%26meid%3D69b80d3bf80e4e23b3c577c6c1034a27%26pid%3D100008%26rk%3D1%26rkt%3D12%26mehot%3Dpp%26sd%3D113207571600%26itm%3D291696721009%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3Ddefault&_trksid=p2047675.c100008.m2219

The check valve was some used fuel check valve with 8 AN fittings from a person that sold used aviation parts off eBay. Any check valve made for fuels that stays closed, one way, even with no backpressure, will work.

I've had this on my car for about 8-10 years now. No problems.

That is true but the vent line can be much smaller than the fuel line size. Fuel cells often come with a #8 vent line but the vent line doesn't need to be anywhere near that size. 1/4 inch vacuum line should be fine.

As Andy stated, rollover valve, #8 hose not looped but an arch. A loop can act like at trap if fuel gets in it and it won’t vent right. I ran my vent to the rear of the car. I put a piece of scotch pad in an old Russell fuel filter, vents fine, no fumes in the garage.

try this : https://www.ebay.com/itm/0-100-PSI-...lief-Valve-Control-Devices/291696721009?

It may be hard to set a 0-100 psi valve to just 1 or 2 psi... a 0-20 or 0-10 would be much better. If there is one available

If you vent under the car do what Chrysler did on some cars - place the vent opening inside the rear longitudinal.