Is the TJ fuel cap non-vented?

[sierradmax]

I'm buttoning up the installation of a motobilt in-cab fuel cell for one of my builds. I welded a 1.5" metal hose neck onto the motobilt tanks cap for remote-fill from outside the jeep. And, I modified the factory fuel fill to accept a 1.5" hose and retain the factory gas cap. During the process, I had provisions to use an in-line fuel check valve inserted into the 1.5" fuel hose. This in the event the jeep was rolled onto its side, little to no fuel would backflow.

However, After the install and I attempted to fill, the slope and lack of fuel weight was not enough for the check-valve flapper to permit fuel to pass. So I ask, is the factory fuel cap non-vented?

 

[GATORB8]

On my 06 factory one it has a vent that runs external and rejoins the filler up just behind the flapper, my Barnes tank does not have a check valve in that line.

The rest of evap vents with check valves.

 

[mrblaine]

So I ask, is the factory fuel cap non-vented?

Yes, it is a fully sealed cap. If it wasn't, we'd never see codes for large and small emissions leaks and the oft recommended suggestion to replace the gas cap first.