Slightly rough running engine, gas tank fills with pressure

I suspect you are correct that these are related but it may not be the evap system that is causing the issue.

All fuel tanks have pressure relief systems that will prevent the tank from building too much pressure and also vents that will allow air into the tank but not out so that it does not buckle and get pulled into a vacuum.

So, this means I would suggest starting with two things. First it would be work checking the fuel pressure and make sure that we don't have a great fuel pressure issue.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If the fuel pressure is okay, then I would remove the purge and see if there is build up on the inside of it. If there is, replace it.

Then I would access the pressure relief valve on the top of the tank if it is still hissing when you open the cap.

There is going to be some pressure but not enough to create a large hiss.

I attached all the info below from the manual so that you can run through this and let us know what you find.

Thanks

Okay, thanks for the reply! I found out why the gas tank was not relieving the pressure. Turns out the hose from the valve on the tank was pinched between the frame and fuel line.

I was doing more research and withheld key information out of ignorance. I recently bought this car. It was sitting for a few years and before that, it was in a barn from 2001 -2014. I also noticed a slight whining noise from the fuel pump. I know I could just check the fuel pressure but just decided to get a new pump. (They are about $40. with shipping) Since it is highly likely for a pump to fail if a car sits for a long time and the gas goes bad.

Also, I didn't care to drop the whole tank. I chose to locate the pump and cut the sheet metal from above with an angle grinder. So much easier, and I will weld a hinge and latch to make future repairs easier. Planning on cleaning the tank out too.

I will update as soon as I replace the pump, most likely next weekend.

Attached are pictures for anyone who happened upon this.

Got it. Yeah, that will do it as well and makes perfect sense. Thanks for that update.

I am sure you know this, but I just have to say it, just be careful and have it well ventilated when welding just in case there are vapors in the air.

Looking forward to hearing back and good idea about the hinges.