My check engine light has been on in my cherokee and when I got it diagnosed the code came up and basically said that gas fumes where escaping from my system, so I thought it was maybe a faulty gas cap and tightened it up and it eventually went off but it eventually comes back, and I keep tightening it and it won't go off. The rubber seal seems fine so idk why or where it's still leaking fumes. Idk is there some stupid sensor that might be broke? If you know what's going on dont be afraid to give your 2 cents, I'm sick of that idiot light shining in my face.

 

What you have is an evap leak.

Might have to replace your gas cap. You can tighten that thing all you want, not going to make a difference. It's pressurized.

I've dealt with a lot of evap leaks, each one of them different. If it's not your gas cap, it can be a number of places. Find your charcoal canister and trace all the lines coming out of if. These lines will run from the top of your gas tank, to your charcoal canister, to your purge solenoid located under your hood, and into your intake manifold. You'll be looking for small cracks or holes in these lines. Possibly bad grommets. They can be hard to spot.

Your gas tank gasket could be bad, I've had one of those. You could have a leak or hole at the top of your gas tank, usually not an issue with the plastic tanks. Pay close attention to the steel line that runs from your tank into your charcoal canister. These like to rust out, mine was.

Could be a number of issues. The most efficient way to find them is a smoke test, done by a mechanic. Usually cost around $30. Most are an easy fix. All evap leaks are hard to find.

 

Hmmm maybe I'll hit up a junkyard for a replacement cap and if that dosent work I'll have it smoke tested to see where it's coming from.

 

Just buy a new cap. It's like ten bucks at a parts store.