I'm redoing the fuel lines on my 85 CJ7 rebuild.
I have a 20 gallon plastic gas tank and it has 2 nipples on the top that are vented directly to the charcoal canister. The manual says there should be a liquid check valve and a rollover check valve connected to the vent lines before the line reaches the canister.
My jeep simply doesn't have these check valves....unless they are part of the plastic tank - could it be that the nipple valves on the top of the tank are built-in check valves?