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Q: possible evap charcoal canister

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By the gas cap there is a black like charcoal substance that looks as if maybe an over flow as well. The cel isnt on nor do i smell gas, not sure if i have over filled gas tank please help
My car has an automatic transmission.

A: I've not heard of charcoal appearing by...

I've not heard of charcoal appearing by the filler neck before, but I have seen canisters break up and regurgitate their contents into the connecting hoses, so I suppose its possible that what you are seeing is charcoal from the canister. If you are in the habit of topping off your gas tank, that might be a contributing factor. Many people like to fill their tank all the way up the neck and that can potentially fill the canister with fuel. The canister is designed for fuel vapor and is not built to be full of liquid gas. From now on, when you fill the tank, just run it until the pump shuts off, and don't continue to pull the trigger. That leaves enough airspace in the tank for the fuel to expand when it's hot without flowing up into the lines and canister. If you're not experiencing any other symptoms, it probably won't cause any other problems, but if you smell fuel or see puddles, you should contact YourMechanic and get them to send a technician out to look things over.

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