Charcoal Canister
Thread Starter
Pro
Joined: Apr 2021
Posts: 571
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From: Texas
Charcoal Canister
Guys needing some ideas, I am stumped. I took out my car for 50 mile run in 103 degree weather. A/C was blasting and everything seemed to be running fine. However as soon as I got home, I noticed it started leaking gas through canister on Driverside. I quickly went to fuel tank and loosened gas cap and the vacuum was released. It managed to drip just a little more, then ended. What could be causing this? I checked vacuum lines and they seem to fine.
Team Owner
Joined: Jan 2006
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From: Crossville TN
Could be several items. The vapor recovery canister may not be releasing the vapors to the carburetor (throttle plate fitting). The 'trigger' for that is a "ported" vacuum source which actuates the switch on top of the canister. If no signal, or the switch has failed, no vapors will be sent to the carb. Then, vapors build up until there is excess fluid in the canister. Also, the media in the canister could have become clogged to the point that vapors are no longer captured, so they just condense and leak out. Those are the most likely candidates.
The canister is not 'wizardry' and can be checked-out, repaired, refurbished, refilled, etc. But that is the most likely focus for your symptoms.
The canister is not 'wizardry' and can be checked-out, repaired, refurbished, refilled, etc. But that is the most likely focus for your symptoms.
Pro
Joined: Nov 2023
Posts: 703
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From: Aubrey TX
I just went through this canister headache last week. I replaced the tank vent valve at the back of the car and "refurbished" the canister with fish tank charcoal from a pet store. What year is your car?
Thread Starter
Pro
Joined: Apr 2021
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From: Texas
Could be several items. The vapor recovery canister may not be releasing the vapors to the carburetor (throttle plate fitting). The 'trigger' for that is a "ported" vacuum source which actuates the switch on top of the canister. If no signal, or the switch has failed, no vapors will be sent to the carb. Then, vapors build up until there is excess fluid in the canister. Also, the media in the canister could have become clogged to the point that vapors are no longer captured, so they just condense and leak out. Those are the most likely candidates.
The canister is not 'wizardry' and can be checked-out, repaired, refurbished, refilled, etc. But that is the most likely focus for your symptoms.
The canister is not 'wizardry' and can be checked-out, repaired, refurbished, refilled, etc. But that is the most likely focus for your symptoms.
Melting Slicks
Joined: Oct 2003
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From: Chapel Hill NC
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I think you can get replacement cansister for a 1980. I could not for my 1971 a few years back so i removed it, plugged all the lines and went to a vented gas cap.
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From: US-PNW
Firstly, I'm not familiar with the charcoal-evap system after '74 when GM got rid of the separator and changed the hose routing.
That said, no matter the year, the canister should not have liquid fuel in it - it's only intended to store vapors until they can be purged through the engine combustion. The question at hand is why is there fuel in the canister? The answer for a '71-'74 would that the liquid/vapor separator valve is not working. How the 1980 system works in this regard is what needs to be examined. Later C3s also came with fuel tanks with bladders -- might a deteriorated bladder be playing a role?
That said, no matter the year, the canister should not have liquid fuel in it - it's only intended to store vapors until they can be purged through the engine combustion. The question at hand is why is there fuel in the canister? The answer for a '71-'74 would that the liquid/vapor separator valve is not working. How the 1980 system works in this regard is what needs to be examined. Later C3s also came with fuel tanks with bladders -- might a deteriorated bladder be playing a role?
Race Director
Joined: Mar 2017
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From: Virginia
I'd love to speculate further, but without knowing if the tank was over, or under-pressurized, it seems pointless.
When you cracked the fuel cap, did air rush out, or is it possible it rushed IN?
Was your fuel tank full to the brim at the time?
When you cracked the fuel cap, did air rush out, or is it possible it rushed IN?
Was your fuel tank full to the brim at the time?
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Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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I deleted my charcoal canister many, many years ago. And it has never given me any trouble since.
plug that line, vented gas cap. Done. Oh, and get rid of some unneeded vacuum lines.
plug that line, vented gas cap. Done. Oh, and get rid of some unneeded vacuum lines.
Thread Starter
Pro
Joined: Apr 2021
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From: Texas
Also, started only filling tank to about 85% no more.
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You shouldn't need to do that. The fuel tanks on these cars isn't exactly huge in the first place. I fill mine right to the very top every time. Never an issue.
So, plug the vent line heading into the left quarter panel and run a vented cap. Or find and repair the issue knowing your a very good citizen keeping that pollution control equipment working properly.
But short filling a already small tank seems a poor solution.
So, plug the vent line heading into the left quarter panel and run a vented cap. Or find and repair the issue knowing your a very good citizen keeping that pollution control equipment working properly.
But short filling a already small tank seems a poor solution.