Has anyone added / used a carbon canister to vent the gas tank and did you find any benefit?
On my last Cougar, the garage had a slight gas smell as car was parked. I assume this was from gas tank venting or potentially fuel evaporating from carb. The rubber for the fuel line & gas tank neck can probably contribute and need to be checked/replaced if needed.
Hi @Cheese I thought I’d chime in I was smelling gas and did some digging and found that my 69 Cougar fuel line had a leak were it ran through the torque box. Just thought if you hadn’t found the smell that would be a good place to look. Good luck.
No leaks / cracks in any of the rubber lines. My thought was the smell coming from either the gas tank vented cap or carb….or both.
I only brought up potential use of the carbon canister for a tank vent as I’ve seen it pop up on my Facebook feed and on some of the FI installs.
As mentioned, this was for a past car and was curious if anyone here has tried a carbon canister.
No leaks is a good thing I only mentioned it because I was smelling gas changed all the lines and still smelled gas on mine and it turned out to be the line running through the torque box. I have just finished installing new torque box’s that’s how I found it. I do not get an any smell from around the gas tank thankfully.
Is your garage well-ventilated?
It could also be bad gas. The newer fuels with Ethanol don’t last very long in a storage situation, they attract moisture, and they are very bad for rubber hoses along the fuel lines.
Nope…fresh gas, and typically use the Ethanol free version.
If you have the correct gas cap there should be no appreciable fumes. The cap only allows air into the tank not out. I typically find tiny hidden leaks. One of my favorites is the accelerator pump under the front bowl. You probably won’t find liquid gas, just a funny looking stain.
When the new car arrives, I have a carb reseal kit as I’ll probably need to rejet due to altitude anyways. Hopefully I don’t have this issue with the new car, but still worthwhile to check out the fuel lines / rubber.
In the end, it appears carbon canister are in limited use.
Been a few months since this was posted, but thought I’d add this. Saw this Cougar XR7 427 side oiler at Barrett’s Scottsdale 2025 auction at the vendor’s Shop48 display, showing the fuel charcoal canister in the trunk, mounted on a vent line from the tank. It’s marketed to stop fuel odors while storing your ride in a garage. With a fuel cell mounted in the trunk, it must have had some sort of fuel injection system type of carburetor for the 427? https://www.youtube.com/watch?v=4pJhma5Y_40&t=50s
I’ve seen that being used by some over in the Vintage Mustang forum. This addresses gas fumes as gas expands and pressurizes the tank…it does require a vent line. Some have also used factory canisters from different cars and those also have a purge capability which most old cars can’t use.
Even back in our cars days, the fumes collected in the charcoal canister were sucked into the intake by vacuum and burned. The system is actually not vented and uses a non-vented gas cap. Oh wait, I bet you meant the system requires a fuel tank vent line to the canister.
Looks like I misspoke…i agree newer vehicles pull the vapors from the canister and pull into the intake by whatever mechanism to burn them.
This Vapor Trapper doesn’t have a way to pull/extract/purge the captured vapors, so the activated charcoal has to be replaced at some interval.
I see others making homemade canisters using PVC pipe, threading both ends for fittings, and using activated charcoal.
This only addresses the fumes coming from a tank as fuel expands and allows it to vent to prevent pressurizing the tank. It doesn’t address fuel evaporating from the carb vents.
I agree - the carb fumes are the big offender! In addition to the vents, my 4100 carb and my original Cougar’s 2100 carb percolate fuel into the intake after shutdown on a hot summer day. We used to think nothing of it, but compared to fuel injection, carbs suck!
“but compared to fuel injection, carbs suck!”
I remember my first fuel injected car. It ran as good when it was cold as when it was warmed up. Being in Michigan I really liked that.
A properly adjusted carb is good. Not great or excellent, good. For me that “goodness” is part of the time machine effect I like in my cars.
And since my oldies don’t get driven below freezing, a carburetor’s “cold” engine performance is good enough.
Back to the topic, hoses and accelerator pump diaphragm are the most common offenders. Also make sure your float level is set to the carb makers spec for your applicatlion.
I noticed a reduction in fuel smell In the garage after the sniper install. Typically the smell was always coming from the carb via a small leak on a gasket or acel pump. A canister will not help with anything like that.
Yes, I found that same carburetor accelerator pump gas leak Bill, after the Cougar sat inoperative on jack stands for 4 years while undergoing other repairs (front suspension, steering pump, box, valve ram and hoses, brake master cylinder leaked into the booster, rear brake wheel cylinder leak, rear wheel bearing axle seal leak). Drained it’s fuel system and freshened the rubber fuel lines, got it running again to find gas leaking from the accelerator pump at front of carb like you mentioned, and out the throttle shaft after shut down. Sorted that with a carb rebuild kit, and been good now for 3,000 miles. Found another gas leak at the tank’s sending unit a few months ago shortly after the gas gauge started reading E. Got that leak solved when you rebuilt and calibrated my FoMoCo original fuel sending unit. Found the 14 year old replacement sending unit’s brass float was full of gas and the rubber seal leaking. Your sending unit rebuild is reading spot on now Bill, and no leaks, thank you! 
I’d check every inch for tiny leaks first, especially around the carb and pump. If everything’s dry, a simple vent line hooked to a carbon canister really cuts the garage smell.