I missed the original post, but that is a check valve for the emissions
canister. I have seen those leak fumes before.

I am not sure about the books for those things... The book for my CJ
shows the valve in line like yours, but mine 'is' on/in the tank and the
only YJ one I have seen was up under the wheel well like yours.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

DougW wrote:
>
> Miguel did pass the time by typing:
> > My son's recently acquired '90 YJ (4 cylinder, 5-speed) has been
> > smelling of gasoline, and a little checking revealed a broken valve
> > tucked up inside the body behind the right rear wheel well. I have a
> > factory service manual and have studied it carefully but can't figure
> > out the purpose of this valve. It looks to be a check valve, on one
> > side there's a line going to the fuel tank and on the other side
> > there's a vacuum hose that runs up to the engine compartment. I
> > thought mabe it was a rollover valve but according to the manual those
> > are supposed to be attached the fuel tank.
> >
> > What do I ask for when I go to the dealer to get a replacement?
>
> From what you describe that sounds like the line that vents the fuel
> tank to the charcoal canister up front. It's a check valve that allows
> fuel vapor to run up and get trapped in the canister. The vapors are
> then sucked back into the intake when the engine starts.
>
> Part of the emissions control stuff.
>
> --
> DougW