With all the great things I've learned by reading the HAMB over the years, thought I would share a solution that worked for me. You know how it is, park your favorite hotrod with its vented gas tank in the garage and the gas smell slowly drifts throughout. Here is what I did...along with a few pictures (I know how we all like pictures!). The black ABS pipe and fittings are merely put together as a canister in which I placed a gauze bag filled with activated charcoal (charcoal for aquarium filters is what I used). The inlet enters at the top (left side in photo) and the outlet (right side in photo) also enters the top but has a line inside the canister that goes to within a 1/2" of the bottom (kind of like an upside down radiator overflow tank). The outlet hose is then routed out the trunk and under the car. The screw cap on the top of the canister allows me to open it up so I can replace the charcoal every year or so. The real cool part, is the little black and grey fitting before the canister. It's a blow off valve from Mercedes Benz part #123-470-03-93 (It was about $25.00 here in Canada, so it's likely to be about $5.00 for all you Americans). It holds pressure in the tank until it reaches about a pound or so and then it allows the gas tank to "burp" (or fart) thereby releasing the pressure. I no longer have or at least haven't noticed the gas smell in the garage (perhaps if I was around when the tank burped or farted I would notice a short period of smell...but that's kind of like when your buddies show up in the garage and release their trapped gas!...A lot of complaining in the moment, but it dissipates in time). Hope this tip helps someone.
Your not using a vented cap I assume? Important for others to know. Just the burp valve alone is worth a lot with today's fuel.
Not a question really, but I kind'a wonder if there's a partial benefit to just using the "burp valve" with no canister. (?) I'm not knocking your solution. I'm sure it works as advertised. And speaking of the burp valve, does it allow intake of air as the tank level drops so no vacuum is created?
I made the canister first...but found I still had some gas smell. When I found the burp valve, I just added it to my vent system. I'm sure it would work without the canister but when it burped, the gas smell would be a bit stronger. Yes, the valve free flows into the tank so no vacuum in the tank is created.
This post has me thinking it may be a solution to a problem common to all '40 Fords and possibly other cars. My '40 is just like all those of other owners I mentioned this to. They use a vented cap, and also have a vent to release air trapped in the tank during fill ups. This vent returns to the fill tube just below the mouth of the fill tube, whose cap is on the almost vertical side of the fender. And invariably when you fill up and try to get it as near full as you can without any gas spilling out, just before you stop pumping the vent burps and kicks gas out onto the side of the fender. If that vent was separated from the fill tube and plumbed up as you describe, the tube hole for vent into fill tube plugged up, and a non-vented cap installed, it would most likely eliminate a most annoying problem.
Never heard of the burp valve before but that is worth hunting for. The canister also acts as a filter for the air drawn into the tank to replace the gas and that is the other reason you want the canister. As for as Dirty old Man's question I don't think that will work as you can't flow enough air fast enough when you fill the tank.
I don't see why it wouldn't work exactly the same for Dirty Old Man's 40 Ford as it does for my roadster. Assuming, as he says, he would disconnect the current vent tube at the filler neck (so there is no longer a vent line in that area to puke fuel as the tank nears full), plug where the hose was connected on the filler neck, change the cap to non vented and add the burp valve, canister and then vent the outlet under the car. The only possible hiccup that I see is how fast fuel can enter the tank during a fill. On my roadster the fill neck is a straight vertical drop to the tank. None the less, I still tend to fill the tank more slowly than on my daily drivers just to be safe and avoid any fuel back-ups onto my paint while ensuring the tank is full (I can hear the different gurgle sound as the tank nears full). @dirty old man, it wouldn't be an expensive experiment to give it a try and might solve a long term irritant.
Looks like this little solution will be going in the ol' "mental toolbox" for possible future usage. Great and simple idea!
I've had the same thoughts about the airflow capacity out thru that burp valve, but it's such a PITA to fill up, and not necessarily get the last cupful in, but to even get within a quart or so of full, that I'm thinking of giving it a try. Maybe a larger hose and 2 valves in parallel?
I cut the reply short for a reason. A fill vent is way different than a vent only type system. A fill vent needs to allow for a large volume of air to get by where as a vent that is only bring make-up air in is small by comparison. Also a fill vent can at times have fuel coming along for the ride as well. So a make-up vent mount high would be better even if it means needing to add a 2nd source of venting.
This is a really nice setup, and one I think I may copy for my own car. To be clear, the vacuum line from the charcoal canister is connected to a ported vacuum source, NOT manifold vacuum. Is that correct?
I did not connect the line from the vacuum canister to engine vacuum of any sort. Mine is simply routed up high inside the quarter panel and then vents under the car in front of the rear wheel through a hole I drilled along side the trunk floor.
he wrote that he routed it out the bottom of the car. but it could be plumbed to the air cleaner. he typed faster than me.
I like the idea of filtering the vent line. The Olds I just picked up has a shaved filler door and fills through the trunk, so I want to keep fumes out of the trunk area as much as possible. I certainly don't mind running the vent outside, but the idea of plumbing it up to the air cleaner to draw some of the fumes out of the canister is an appealing thought.
I know this is an old post but it is worth a shot. I am doing the same set up right now and I can't find anyone that has that part in stock. Anybody have any idea where to find that little "burp" valve or something similar? Mercedes purge valve - 1234700393
Hey @keeper , when I did the install in my car, I just ordered the part number from a local Mercedes dealership. A week later it was in...but that was before the current supply chain issues, so I can't help much more than that.
@keeper, I just did a google search with Mercedes Benz part number 123-470-03-93 and all kinds of suppliers showed up...but I didn't dig deep enoigh to tell you whether any of them had stock on hand.
You might look here: http://www.oldbenz.co/mercedes-purge-valve-1234700393 Or here: https://www.ebay.com/itm/284310719709
I use a new fuel filter. I run a hose to the tanks vent port, put a loop in it with the filter at the end. Then mount the filter above the tank. I also use a vented cap.. El Caminos are well known for gas fumes, this is the only thing that worked for me..
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