RallyBoy1

Hello all! I am having a problem with excessive gas tank pressure. The problem I am experiencing is abnormal. I am not getting a code. I blew through the line that runs from the charcoal canister and connects to the vacuum switch which connects to the purge solenoid. The line was not clogged. Could it be the pressure control valve that is causing the issue? I am not getting any gas smell at all, just lots of abnormal pressure when taking the gas cap off.

Also, if the evap solenoid wasn't working, would I get a check engine light? How do I test the evap solenoid and the vacuum switch for proper operation? I don't have a device to pull vacuum.

mad95z

Is this causing drivability or performance issues?
I always hear a "woosh" when unscrewing the gas cap, especially during hot weather. Its just your 383 with Le2 heads telling you you need a bigger cam!

ascastil

I get a lot of pressure in the fuel tank also, but its only in the summer time when it heats up. I was researching this last summer and I read somewhere on here it could be the evap emission pressure control valve located in the rear of the car by the filler neck. I havent ever gotten around to going to the junk yard and getting one to swap out to see if it works, plus, its gonna be hard to fit your hand in there to disconnect it. Heres a link courtesy of Shoebox.
http://shbox.com/1/evap_system.jpg

ACE1252

It's not too terribly bad to work in that area. I replaced all those rotted hoses a couple of years ago. My biggest problem was not being able to find the proper fuel rated hose around a 3/16" I.D. in size(may have to replace them soon due to fuel vapors eating them up...don't know if they are hold up...will have to check). 1/4" and 5/16" I.D. fuel hose(non-fuel injection rated) will allow you to replace all the hoses without breaking the bank.

My thread on the issue....
https://www.camaroz28.com/forums/gen...-p1441-697461/

Here is post #13 in the above thread....

Guest47904

The tank has a vent valve. check it. http://shbox.com/1/fuel_pump_wiring.jpg

ascastil

The vent valve looks much easier to replace. How would one verify its working correctly? A pressure control valve or a vent valve seem like either could be related to excessive pressure in the fuel tank.

jcsmith1995Z28

Im having excessive fuel tank pressure aswell, and not knowing why I let the pressure off by the fuel rail check valve, till there was no more pressure. Then I started the car and drove it, it was falling on its face at the slightest imput of the gas pedal.
It then died , and will not start back up. I rechecked the pressure at the check valve and it was at 40psi..car has spark. Before I messed it up, it was getting very hard to start. Thought it was the fuel pump. any help would be greatly appreciated, its a 1995 z28 and its my daily driver

94Z28LS1toLT1

hey man i was reading ur post and im having the same thing my tank builds alot of pressure after driving for a while but did u fix ur issue

RobsWS6

Mine was doing this as well. What fixed it for me was to stop running gas with ethanol. After one tank of ethanol free gas, the tank pressure was back to normal and has been ever since I switched back.

I took the WS6 on a 600 mile round trip and had to ethanol again and my tank pressure was crazy high again. So I ended up just putting the gas cap snug and didn't tighten to 3 clicks like normal. No tank pressure.

I run ethanol free gas as much as possible and don't have that issue anymore.