This wasn’t recent, but thought it was a worthwhile post to get this community kicked off.

A while back, my car (2011 Kia Optima) started having an issue where the gas fill nozzle would click off early during fill; I would have to fill slowly which was extremely annoying. I did all of the basic troubleshooting I found on Google with no results. I ended up fixing it, but it was a very difficult problem to track down, so I was particularly proud when I solved it, especially at no cost.

EVAP was just a nebulous term to me at the time, but I started really digging into the service manual and systematically testing things like canister blockage, purge solenoid operation, anti-siphon blockage, etc. I even made a special apparatus that allowed me to blow air (with my mouth) into the gas fill neck to rule out some final suspects.

It turned out the problem was the vent valve (ORVR, “B” in the picture) in the tank. After ruling everything else out and convincing myself it had to be that valve, I dropped the tank and removed/disassembled the valve. It works like a float, an open vent until the tank is full, but it was stuck at the top because it had swollen in its cage for some reason.

I sanded the float down just slightly, reinstalled it, and never had an issue since. Maybe it was a batch of bad gas that made it swell?