I took my 91 Z28 out of its winter hibernation and took it out for about a 130 mile drive today. I had forgotten, but last fall I noticed I kept smelling gas after the car had been running for ~30-40 minutes.

Today, I smelled the fumes just like I did before and I kept opening the gas cap at each overlook (scenic car ride, lots of stops_. Everytime, there was substantial pressure that was released and the vapors coming out were pretty hot coming out.

The other thing I noticed that whenever I'd shut the engine off, I'd hear boiling; coming from the tank!

The car ran normally all day, with no noticeable issues with the fuel pump.... UNTIL - When we went to leave from the last stop, I turned the car on and the pump groaned much lower than it had done normally - I got out of the car, opened the cap (basically took it all the way out) and proceeded down the road... Then the sputtering started - The fuel pump wasn't pumping enough fuel and within 30 seconds, the car died on the side of the road... I sat for a minute, started it up again and it ran fine and got me home.

Obviously I am having venting problems, which is basically turning my tank into a pressure cooker. Could this simply be from a bad vent on the tank? I've not checked anything out on the charcoal side of things, but I can't imagine that if the vent worked properly the charcoal canister could be causing this issue.

Any help would be advised.

 

I would think if the tank is over pressured or getting sucked in, there is a vent problem...

I put the gas cap on just enough to not vibrate off, & havent had the pressure problem. When spring comes, Im getting a vented cap.

I know nothing about the cannister, so I have no .02 on that issue, sorry.

I know, I owe you 1.5cents!! LOL

 

Just had the same problem today to the point when the tank did vent it blew out 7 gallons of fuel my problem was fixed with a new fuel filter

 

I replaced it just now - We'll see... hopefully the next time I take a longer trip, the gas smell goes away and I don't hear the fuel boiling...

Does anyone have the GM part number for the tank vent?

 

Part number is posted in an older post search for tank pressure

 

If you remove any of the heat shielding between your exhaust and your fuel tank it will also cause the problem you are describing.