The pipe u r talking about is not open infact it goes in to an inlet into the tank. i have checked all the pipes on the sides and they were all connected and doesnt smell.
i am facing the same issue and the only culprit if the charcoal canister in the engine room.
the solenoid sucks the fumes only when it goes over 1800-2000 rpm and the charcoal in most mehrans are already choked.
change it and u will find the issue gone.
What i did is i blow air into the inlet pipe and found approx half cup water getting out of the lower drain pipe of the canister. it means that the charcoal has managed to absorb the moister in the fumes coming from tank. after that there is lesser smell. now i will blow air thru some pressure and see the result after that.
lets hope it resolves other wise i have to find a canister or make operation of the canister talking help of youtube.