C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

C3 Fuel Tank Vent?

Old 03-10-2019, 03:31 PM
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Default C3 Fuel Tank Vent?

Please tell me how gas fumes vent from a C3 fuel tank. I have a 1968 and when I recently removed the gas cap, to fill the tank, an unbelievable geyser of fuel shot into the air! Will a new gas cap fix the problem? Thank you.
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Old 03-10-2019, 04:02 PM
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I'm not sure if '68's had vented gas caps or sealed. On my '71 my tank is sealed and the tank is vented through a line that runs up the drivers side frame rail to a charcoal canister behind the left wheel well (Evaporative Emission Control system ). Then there is a vac hose from the can to the carb. Might want to find someone with a '68 to confirm what vent system is on a '68 as '68's are a little different and I don't know when the government mandated a closed fuel system. The EEC system was one of the first pollution control systems. If you have a copy of your owners manual it might talk about emission control devices on your car and the AIM would have it as well.
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Old 03-10-2019, 06:05 PM
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68 and 69 are vented through the gas cap and do not have a charcoal canister.

70's have a sealed tank and vent through a valve on the left side of the fuel tank and do not have a charcoal canister. They vent to the atmosphere (except CA cars which had a canister).

71 and later have a sealed tank and vent through a charcoal canister.

I have no clue if a new gas cap will solve your spraying gas issue, but that's where I'd start.

Last edited by Iceaxe; 03-10-2019 at 06:15 PM.
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Old 03-10-2019, 06:10 PM
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The cap should say vented on it.
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