Gas Tank Vent Help

Good evening all. I am having a problem with venting my gas tank and I need some help. I have a 74 CJ5 that I have put a 98 TJ 4.0L in it. The original 74 was a big mess and really nothing was salvageable other than the dash, hood, steering column, and tranny and transfer case. I ended up putting on a repro body I bought from Willys Overland. I also replaced the gas tank. Since nothing was salvageable, the charcoal canister was cracked and not reusable and there was no check valve, or if there was at some time, it was not there when I pulled off the body. I am running an external fuel pump and for the regulator I am using a Jeep Grand Cherokee fuel filter/regulator. The two vents on the side of the tank I have plugged off because I have no where to run them to.
The problem I am having is that when I remove the gas cap, I have pressure relieved that has built up inside the tank. How can I vent the pressure out of the tank. I thought of a vented gas cap but that only lets air in for when fuel is used up. I take the Jeep off road and also to mud runs so the solution will have to keep water out of the tank.
Any help would be greatly appreciated.

 

You need to charcoal canister along with a liquid check valve.

using a 4.0 engine you will have more pressure os gaz going trought the line, and more volume is gonna get back to the tank. You have more vapor created than with the carb engine.

 

You cannot run without venting the tank. Won't work. Air has to go in and out in response to temperature change as well as when the pump pulls fuel from the tank.

Older cars used a vented cap. It has a labyrinth in the cap that lets air and fumes past but blocks slosh (mostly).

You can run a vent direct to the air at a point higher than the tank if you want to. A fuel filter open at one end makes a good cap for the vent.

You can also run vapor recovery, with a charcoal canister. It's not complicated. Pick a suitable canister at the junkyard, and connect as shown in the TSM. You'll also need a liquid check valve to stop liquid fuel from reaching the canister. None of this is specific to Jeep - just look for parts that will work at the junkyard.

 

Here's a really common canister - RockAuto

which uses an external purge valve - RockAuto

Not the cheapest to buy new, but there are plenty of Chevy pickups in the yards.

Looks like the external liquid check is not a common part. I think that most of the manufacturers have gone with a check valve that inserts in the top of the tank. There is a replacement for the original Jeep LCV, but it's not cheap - check MTS.

 

Great info guys, thank you. I will start looking.