I detect a gas smell every time I fill up my car. I'm thinking maybe it is either the vapor canister or the EVAP system.
A common issue on the Mustangs occur on the fuel tanks, there is a rubber gasket where the filler neck enters into the fuel tank. It can crack and the smell of fuel can occur as the tank is filled. It is also possible a cracked EVAP line of canister housing is leaking vapor during tank filling. The fuel system needs to be inspected and the fault codes read out of the engine computer to determine if there are any EVAP codes stored. You may want to enlist the help of a mechanic, like one from YourMechanic, who has the equipment and training to locate evaporative system leaks.
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