Vented gas cap for EVAP delete?

[caddisguy]

It's a bit of a long story, but the TLDR is I let the wrong shop chase a P0455 on my 2003 TJ a few years back.

They parts cannoned it and nothing worked. Ultimately I believe they flashed the ECM to ignore EVAP codes. I don't even get a pending code driving around with the gas cap loose or purge valve disconnected.

Since then I've been through a couple gas tanks and recently an epoxy repair (on the plastic rim the filler neck connects to)

The EVAP system seems plugged and my hypothesis is perhaps this is causing the tank to build up vacuum and causing these frequent tank failures. I will make that the first question. Is this a reasonable hypothesis? Or "no way caddisguy... EVAP system can be fully plugged and it will never build up enough vacuum to cause any damage"

And the second question of course (if applicable) is whether or not a vented gas cap could solve for this? I don't have emissions testing where I live, so if this is a possible solution it would save me the trouble of figuring out where the problem is and probably trying to chase down another charcoal canister or something.

If the answers to the last two questions are yes, are there any vented gas caps that would fit a 2003 TJ or would I have to make my own?

Appreciate any insights and thank you in advance!

 

[Chris]

I think you're onto something with the frequent fuel tank failures. That's not a common issue. In fact, I've never heard of it until now.

Given all the issues an old vehicle can have, the EVAP system seems like one of those things that is better off just being dumped. Sure, I know there are environmentalists that will argue with me, I simply do not care.

I thought about doing the same thing to my TJ when I had it. You can't even get replacement parts for much of the EVAP system anymore anyways. I was going to come up with my own system and find a vented gas cap that fits. I didn't get far enough down the rabbit hole before I sold the TJ, but I can tell you that I don't know off the top of my head if there is a vented gas cap that will fit, but I'd bet dollars to donuts it wouldn't be hard to find one that did.

Gas caps are for the most part a common size and finding one that fits should be easy.

 

[caddisguy]

I think you're onto something with the frequent fuel tank failures. That's not a common issue. In fact, I've never heard of it until now.

Given all the issues an old vehicle can have, the EVAP system seems like one of those things that is better off just being dumped. Sure, I know there are environmentalists that will argue with me, I simply do not care.

I thought about doing the same thing to my TJ when I had it. You can't even get replacement parts for much of the EVAP system anymore anyways. I was going to come up with my own system and find a vented gas cap that fits. I didn't get far enough down the rabbit hole before I sold the TJ, but I can tell you that I don't know off the top of my head if there is a vented gas cap that will fit, but I'd bet dollars to donuts it wouldn't be hard to find one that did.

Gas caps are for the most part a common size and finding one that fits should be easy.

Thanks Chris! I really appreciate the response.

I started my search for a vented gas cap that will fit the TJ. Seems like a bit of a struggle so far and AI can't come up with anything.

Worst case I could probably just do a similar mod that I did on a chainsaw with a damaged tank. I found some 6mm (outside) 3mm (inside) fuel line that fit a duckbill check valve perfectly, then attached it to a vent screen through some heat shrink (hilariously heat shrink that came with the OEM wiring harness replacement for the multifunction switch) and epoxied that to the tank. Tested pressure (which held fine) and vacuum (no buildup) and that patch job has held up for a few years now despite all the sawdust and vibration. I think the same concept would work drilling a hole in an OEM or aftermarket TJ gas cap and installing the same. I have one of those aftermarket gas cap covers too which would keep out most of the dust and prevent the vent screen from getting clogged.

From what I read though, these vented gas caps allow venting in both directions (vac and pressure) ... I imagine because on a hot day there is thermal expansion and vapors can build up pressure.

Hopefully I'm able to find a vented cap that will work for sure or maybe someone will chime in... but hey I modified a chainsaw with Jeep parts so doing Jeep mods with chainsaw parts doesn't seem too far fetched.

 

[macleanflood]

I'm assuming you have some intact fittings on top of your tank?

I'd run a hose to a check valve up the filler neck to a small air filter like a lot of folks do for axle vents.

If you want to reduce the gas fume smell run it through a charcoal cannister like the Duralast VC120...but you'd have to find something smaller.

I disagree that evap parts are not available.

I'd sent my PCM to @Wranglerfix to get the EVAP back on it, and just replace all the fittings, hoses, solenoids and charcoal cannisters and put it back stock. Just because the shop failed doesn't mean you can't fix it. I'd fix it mostly because driving an open top Jeep that reeks of gas vapor absolutely sucks to drive or store in a garage.

-Mac

 

[Wranglerfix]

@caddisguy I can reflash your exam to OEM stock programming with same day turnaround time. You can then figure out what’s going on with the Jeep.