Thread: carbon canister on a GM vented gas tank

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Originally Posted by russ35

I have a 35 Chevy with a stock gas tank. When I park it in my garage I can smell the gas vapors from the gas cap. I installed a carbon canister connected to my carb. I have the solenoid connected to the brake light. When I step on the brake the vapor is pulled out of the canister. If I drive on the highway for awhile no vapor is drawn out so I can get into a vapor lock situation in the carb. I remove the cap and I can go again. The vent is blocked on the gas cap. Should I have the solenoid open all the time when the engine is running, or should I install a vented cap to break the vapor lock? Has anyone had this issue before?

Something doesn't add up. You start out by saying that you can smell gas at the cap while it's parked in the garage, but then say it isn't vented going down the highway. As far as I know, caps are or aren't vented. Can't do both. So I'm wondering if the fumes are actually from somewhere else.?.? And I can't say that I've seen or heard of the use of a brake activated solenoid to purge a carbon canister.... how did you come up with the idea?

Sorry for the confusion. The cap was originally vented. Because I had this odor problem I had a guy install the carbon filter. This filter set up needs to be re-designed. They connected the solenoid to the brake wire that opens the vacuum line from the carb to draw out the vapors. I now have a non-vented cap (plugged with some rubber) with a canister and a vacuum line to the carb. The vapor line comes off the tank neck to the canister. Any ideas how this could work?