Gas cap

[Nick0187]

So I got the dreaded gas cap light. I was reading a few forums and wanted to ask a quick question. My ram came with an aftermarket gas cap so I replaced it with what I thought was an oem mopar cap at least that’s how it’s advertised. The light is still on after a few days of driving. My question is that when I unscrew the gas cap now there is a big woosh of air being sucked into the tank as if there is a vacuum. Is this normal? Should I get a different cap or are there other issues?

 

[MarshRam]

I don't know, but have you tried removing the tether? Worked for me, I was having problems for months and no problems since I removed it.

http://www.ramforum.com/threads/gas-cap-light-and-cel.111309/#post-1609599

 

[14RAM1500BG]

Many times it will throw the gas cap code when it detects a small leak for the first time. Many times it isn`t the cap.

 

[Nick0187]

The dealership ran a smoke test and it came back good.

 

[bigdodge]

That tether is definitely part of the problem. I also used some fine steel wool on the sealing surface to clean it up. Also after it clicks I will push firmly on the cap and turn it more to make sure it's tight. Seems to help

Sent from my Pixel 2 XL using Tapatalk

 

[Nick0187]

It seems like the vacuum is very good with a very tight seal on the cap. Is there supposed to be a relief valve on the cap or some part of the system? The loud woosh of air being sucked in is a concern to me

 

[MarshRam]

It seems like the vacuum is very good with a very tight seal on the cap. Is there supposed to be a relief valve on the cap or some part of the system? The loud woosh of air being sucked in is a concern to me

I think mine does that when it is hot out, I could be wrong, it's been awhile. I would definitely try removing the tether first, but that may not be the issue as it sounds like you have a good seal. Worth a try, it's free!

 

[Nick0187]

I don’t understand why there is so much vacuum in the tank. I’m worried about damage being done.

 

[MarshRam]

Idk, I'm trying my hardest to bump it for you buddy, someone has an answer!

 

[bigdodge]

I don't notice any vacuum sounds but it hasn't been above 60 here since I got the truck

Sent from my Pixel 2 XL using Tapatalk

 

[billyw]

I've never noticed a vacuum whoosh. Doesn't sound right to me.

 

[Nick0187]

I thought it was strange as well, I live in Chicago where it is cold so weather shouldn’t be an issue. I went to the dealer today to get a true oem cap, that didn’t help either. If the cap doesn’t vent, then I assume there’s another vent valve somewhere that is clogged or not functioning properly.

 

[14RAM1500BG]

I don`t know a lot about it but the evap system doesn`t vent to the atmosphere from what I understood. My other truck had a purge solenoid replaced and they blew out the lines to it when I was having issues. I would discuss your issue with the dealer and see what could cause the pressure build up. Sorry I couldn`t be of more help.

 

[Nick0187]

So..... I went and bought and OEM gas cap from the dealership and that didn't help me. So I called back the dealership that ran the smoke test on my emissions system and had them look at it. They forgot a hose clamp on the vent tube!! So problem solved thankfully. Thanks for all your help and ideas.

 

[MarshRam]

Mechanics should be required to pass a stringent memory test. There sure are a lot of forgetfulls out there.

 

[14RAM1500BG]

Simple enough. BTW, did you ever find out why the gas cap leak showed up? Did you get it fixed? Sometimes the leak is so small it is hard to detect even on a smoke test. The system generally points to the gas cap first when a small leak is detected especially if it was detected right after you filled up or added gas to your tank.