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DIY Charcoal Canister

Torkman66

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Full Member
Joined
Apr 3, 2022
Messages
642
There are many different versions of this but I have made lots of these and they work great. Through the years (I'm in my 60s) I have built hot rods, dozens of mustangs, dune buggies, trucks, even corvettes and jeeps. Pretty much anything with an engine and wheels I've tried to get a wrench on it. I'm also a member of many different forums. IN every forum there is ALWAYS lots of discussion about fuel tank venting and gas smell. I will try to cover a bit of history here to help explain what's going on for those who may be new at this.

First, in the 60s and in almost every hot rod I build, there were no vents or charcoal canisters. You either got a big woooshh when opening the gas cap or you drilled a small hole in the cap to vent the pressure off. The pressure comes from the fuel expanding and the fumes are simply the vapors that are produced during expansion. The smell of gas is normally because the system is vented at the cap or with an open vent line tucked up high into the body. Bottom line is that you can vent your tank with a cap or an open vent line, and that will stop the under-pressurizing (vacuum) when gas is depleted or the over-pressurizing when gas expands (gets warm). But it WILL NOT solve the smell of gas problem, especially for vehicles stored in a garage.

I have owned and restored many older 65 and 66 Mustangs. They do not have a charcoal canister. Their caps are mounted on the back of the taillight panel and are vented. The Mustang has a very short fill nozzle (about 10 inches). If you fill the tank full and try to get a few extra pulls in at the pump, you dump gas out the caps vent hole. When the gas expands in the heat, if the tank is "over-filled" it will also run out the cap. By the late 60s and then into the 70s and newer, the vented cap was not as popular and the manufactures went to a charcoal system that both vented the tank and helped remove/reduce gas smell. Some of these canisters, even today, have gotten pretty elaborate. In a 1983 Jeep CJ7, there is a charcoal canister that has a small oneway vacuum pull from the manifold, pulls from the carb bowl, and pulls from the fuel tank and sends the fumes to a T in the PCV tube to be burned. All of that passes through a charcoal bath to capture the smell as well. The system is overkill and has some smog type thinking involved, but it works very well. Most modern cars have something very similar to this setup. The catalytic converter also plays a big role in eliminating fuel smell by "burning" passed fumes in exhaust.

So back to the DYI charcoal canister. I started making them in 50s and 60s cars many years ago to eliminate the smell and to vent the tanks so as not to have a vented cap. I used to make them out of steel pipe, used a sponge instead of steel wool, and had versions that could not be serviced. I have learned a lot from others how to make them lighter, more efficient, last longer, and make them serviceable. Here is how I make them now:
You need 2" PVC pipe and fittings. Only need about 6 inches of pipe and three fittings. I have most of that stuff around the shop so it does not cost anything. Lowes has what is needed for under 20 bucks if you have to buy it all.
You also need some 0000 steel wool, a 3/8 threaded by 3/8 barb fitting (elbow barb works best) and finally the charcoal.
https://www.amazon.com/dp/B0002563VI/?tag=classicbroncos-20

Here is a pic of the PVC stuff. From left to right: threaded coupler, threaded cap that attaches to coupler, cap, pipe.
IMG_7899.JPG


Use the threaded cap (second from left above)and drill a hole in the center on top that is just a bit smaller than the barb fitting.
IMG_7901.JPG


Use a heat gun and heat the top of the cap a bit and then thread in the barbed elbow into the cap. It will work as its own tap and make threads in the cap to tightly hold the barb fitting.
IMG_7902.JPG

I didn't have an elbow barb so had to use a separate elbow fitting and thread barb into it. It is cleaner if you just use a single barbed elbow.

Now take the cap (3rd from left in pic above) and drill several small holes. I use a 1/8 bit. This is the bottom of the canister.
IMG_7903.JPG

Now just decide how long you want the canister to be and cut the 2" pipe that length. The longer the canister, the more charcoal it will hold and the more it can filter. For me, I determine where I want to mount it and then figure out from there how long it can be. On a Bronco it mounts very nice in the passenger rear wheel well cubby up behind the rear fender well in that little pocket between the rear of the wheel well and the taillight housing. Here is a pic of the canister all connected.
IMG_7904.JPG
IMG_7905.JPG


Now you need to take the steel wool and put a mound of it in the bottom of the canister where the holes are and in the top of the cap where the barbed fitting is. The steel wool keeps the charcoal from coming out on either end.
IMG_7908.JPG
IMG_7909.JPG

Now just pour in the charcoal until it is full and screw the top cap on it. Connect the vent line to the barb and mount up above the tank anywhere you want. The fumes go through the canister and down through the charcoal. No more gas smell. It also provides a vented system for the tank to deal with pressure changes and no more need for a vented cap.

Paint it black and build some type of mounting system, I use a piece of sheet metal about 4" by 10" and make a mount similar to how a coil is mounted on the engine.
IMG_7911.JPG
IMG_7910.JPG

The top is a screwed on cap and you can unscrew it and replace the charcoal when needed (every few years). The bottom is glued on.

Finally, if you are running an aux tank, just run the vent line from the aux tank to one of the two vent lines on the main tank and then run a line from main tank to this charcoal canister. It will act as a vent and a canister for both tanks.
 
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jmhend

Bronco Guru
Joined
Dec 25, 2007
Messages
2,742
Thanks for sharing this, I am going to try my best to install this next week.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
35,524
What do you do about the charcoal getting saturated? Just change the charcoal every once in a while? The absorption isn't unlimited.

I remember years ago I did a V8 Ranger project and I kept the charcoal system functional. If I let it sit for a long time the garage would start smelling like fuel. The charcoal would get saturated with vapors and it would end up venting through the canister and into the garage like an open fuel tank. I would go out and drive it a couple hours and that would clear the canister for another session of sitting around. I know I had it right as I got it to pass emissions testing.

If a second nipple was added to the same side as the fuel tank vent and that went to a vacuum source on the engine it would pull fresh air backwards through the canister and clear it out as you drive. The trick it to get the flow without creating the issues you get with a vacuum leak. I think there is a vacuum relay valve out there that would be great. Apply vacuum to one port and it would open flow through a passage. Use ported vacuum to trigger would be perfect. Just need to try and find that vacuum switch/relay doohicky.
 
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Torkman66

Torkman66

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Apr 3, 2022
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That’s basically how most modern canisters work. They have a one way check valve that pulls a small vacuum through the canister and sends it to a T in the PVC line that gets burned. Could be done in this DIY but makes for more lines, canister fittings, etc. At that point might as well just buy a canister or get one from junk yard and hook up all the lines. The mod I have used as presented here provides a vent system and reduces smell. It’s not 100% but it makes a significant difference. And yes it is serviceable. You can change out the charcoal by unscrewing the pipe. I change it out every year or so. Charcoal is cheap…it is used in fish tank filters. I think Walmart has a pound for $12. That would last several years. But yes, a vacuum source would improve this but would also make it more complex.
Here is a pic of one with vac. Charcoal lasts for years.
IMG_7963.jpeg
 
Last edited:

jmhend

Bronco Guru
Joined
Dec 25, 2007
Messages
2,742
That’s basically how most modern canisters work. They have a one way check valve that pulls a small vacuum through the canister and sends it to a T in the PVC line that gets burned. Could be done in this DIY but makes for more lines, canister fittings, etc. At that point might as well just buy a canister or get one from junk yard and hook up all the lines. The mod I have used as presented here provides a vent system and reduces smell. It’s not 100% but it makes a significant difference. And yes it is serviceable. You can change out the charcoal by unscrewing the pipe. I change it out every year or so. Charcoal is cheap…it is used in fish tank filters. I think Walmart has a pound for $12. That would last several years. But yes, a vacuum source would improve this but would also make it more complex.
Here is a pic of one with vac. Charcoal lasts for years.
View attachment 914389
Right makes sense, and if you service it, say at the same time you do a state inspection, then that is your annual reminder.

Sent from my SM-N986U using Tapatalk
 
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Torkman66

Torkman66

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Apr 3, 2022
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Mounted between passenger rocker panel and rear wheel well. Bolted to front section of wheel well on rocker side. Had to shorten it a bit to tuck up nice in that cavity. I ran the vent line from rear tank up drivers frame to the hollow rectangular floor support, inside that tube over to the passenger side right where it opens up to the place canister is mounted. Easy access for any future mx.
IMG_8209.jpeg
IMG_8210.jpeg
 
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