On Friday, March 9, 2018 at 9:23:45 AM UTC-10, Paul in Houston TX wrote:
> dsi1 wrote:
> > On Thursday, March 8, 2018 at 10:42:30 PM UTC-10, Steve W. wrote:
> >>
> >> Show me a car that has a sealed system that actually runs. They are all
> >> vented through the charcoal canister. Water vapor can still get in as
> >> well as the amount that is already absorbed into the ethanol in the gas.
> >>
> >> Dri-Gas can be helpful if you are using gas that has been stored a while
> >> or that came from a store with low fuel sales. Or if you run straight
> >> gas without ethanol like I do in all the small engines and vehicles when
> >> possible.
> >>
> >> --
> >> Steve W.
> >
> > There are valves in the fuel system to equalize tank pressure and the purge vapors from the charcoal canister. It's still a sealed system.
>
> Air must enter the tank or it would collapse during fuel withdrawal.

You are 100% correct about that. That's why there's a valve in the fuel system to equalize tank pressure. My guess is that any air that enters the system through that route wouldn't contain much water vapor.