resharp001

Hey folks, anyone know exactly the venting flow of our fuel tanks? I know the early model evaps were slightly different but I presume it's the same venting flow across all JKs. Started having an issue with the jeep not taking fuel at the pump (kinda resolved). I presume a venting issue. Am I correct in thinking that fuel vapors and venting flow from the tank, through rollover valve assembly, to evap canister, up to the evap purge valve in the engine bay?? Where does the line on the evap canister that connects to the control module go? It looks like it goes up towards the filler neck.

So far I completely removed the evap canister and confirmed there is no blockage in that thing. I removed the white control module, which I previously replaced to fix a small evap leak code, and that does not seem to be an issue. I removed the purge valve in the engine bay and that does not appear to be blocked (recently replaced when I rebuilt timing cuz I had broken a couple clips not knowing how to remove them). So, after confirming those things, the jeep is taking fuel but there is a weird noise while doing so. Make me feel like it is venting, but not properly. It almost sounds like if you were blowing constantly into a soda bottle. I took a short video this morning. It’s a little hard to hear over the sound of the fuel flowing but it’s a drone in the background if you listen carefully.


I know it never made this noise before. It’s a pretty obvious sound as you’re standing there filling up. Anybody have a thought? Most searching results back to early models having a splash back issue and replacing filler necks with new model, or clogged evap canisters. It’s clearly a venting issue to me and really trying to understand the venting process on this system.

Sixty4x4

Not sure Russ. But that sound is like what mine is filling and when full it spits back so I just listen for it when it is near full and slow down the fill rate. I don't have the purge valve at the engine now being a Chev V8.

MountainTrails88

I would think the fill neck is cramped or pinch somewhere. You could have run over a boulder or tree branch and it hit the fuel system somewhere. I have a problem with large rock striking my E-brakes on the wheels.

Mr.T

I had this problem on my '08 early on (about 2011). It turned out to be the vent valve (rollover valve) inside the tank wasn't operating correctly -- restricting vent flow, not opening fully. The solution was replacing the whole tank since the valve isn't a separately available part. I suspected that something rubber or plastic swelled or deteriorated. There were enough problems back then that Jeep would fix it even if no warranty.

On a side note: In Oregon we still have gas station attendants in a lot of areas, and they are so used to similar Jeeps not filling well that they occasionally comment when mine fills normally...

resharp001

I meant to followup on this post. Jeep really wasn't used much in '23 so certainly nothing that crimped any vent tube or anything like that. Had always been working fine, got laid up for a long time while I tore things apart and rebuild timing, then all the sudden this issue.

Anyhow, last week I blew some compressed air down the fill tube to see if I'd vent or just build pressure. I vented and I heard the "gurgling" type noise. From under the jeep is sounded like up in the taillight area, and from the taillight area it sounded like from under the jeep.

In the taillight cavity there is what I presume to be a filter vapors vent from. This appears to be what the evap canister control module vents to -



On the '12+, the line leaving the evap canister travels up towards the fill tube and goes to that filter -



I disconnected the line right there at the control module and blew more air into the fill tube. No noise. The air clearly vents right there too. I have a rubber stopper on my air gun and blew air up through the disconnected portion of the tube. Lot of dust exited my taillight cavity. No noise. I connected the line again and blew air in the fill tube and I got the noise again . I don't know if it's some sort of backpressure or what. Anyhow, on my next fill up I'm getting no noise and the tank is taking fuel. I've topped off twice now and am not getting any noise. Strange.

It is clear to me though that venting is from the tank, up through rollover valve, to evap canister, then if the jeep is off, up through the taillight cavity. if the jeep is running I presume the canister is sending vapors up to the purge valve in the engine bay.

resharp001

Updating this thread.

So the issue turned out to indeed be the actual evap control module. My factory module died years ago and was replaced with a Dorman unit that was good for years. When I was having this fueling issue I popped a new Dorman unit on and I was then able to fuel up just fine, but I had a bad gurgling sound in the process. After a few weeks I decided to swap out with yet ANOTHER Dorman unit. Pretty much same issue. It took fuel fine but I got a sound. Finally decided there had been a change in the actual valve design Dorman was using these days. Decided to buy an actual Mopar unit at the tune of $65, double the Dorman price. She's all quiet now. So, this is definitely one of those parts I'd suggest people just buy the factory unit and be done. The Dormans function fine but they do seem to make a sound when venting.