I own a 1997 740i with 135K and recently it started smelling gas intermittently. The check engine light indicated a P0440 so i started by ordering a new gas cap that i should be receiving this coming week.

However, not 100% convinced the smell was coming from the exhaust i put the car on ramps and sweeped thru the lines and finally i discovered that the strong smell was coming from the opening area of the gas tank that is located behind the driver's seat.

BUT with the engine running i could not see gas leaking from the lines in the vicinity nor can i see gas leaking from the round plastic housing at the top of the driver side rear passenger tank opening...

I am unsure if it is a hazard to keep driving like this so if you have an insights to share with me i would appreciate a lot :)

Also, the smell started some time after a switched from 92 to octane 89, not sure if it relates in any way with the P0440...

Thanks again,