Excess pressure in fuel tank

[hgeranium]

This has been going on a few months now, before then I’ve never had an issue with this. Whenever I stop for gas, especially after driving for a while, there is a ton of pressure hissing out from behind the fuel cap. I know a little bit is normal but it’s much louder and more powerful than I’m used to. You can hear it before you even take off the cap and sometimes it’s so strong that if I’m not careful the force will blow the cap away once it’s unscrewed. Pretty new fuel pump/strainer and fuel filter. Could the vents be clogged allowing for excess pressure to build in the tank? I can get a video of it tomorrow after work 

[Pete M]

is your charcoal canister still hooked up?

[87MJTIM]

Mine was doing the same thing.  The vent tubes got crushed after the bed was removed and re-installed after a restoration.  I dropped the tank and re-routed the lines - taping them in place to prevent movement and getting crushed again.  No problems since.

[hgeranium]

On 10/15/2026 at 9:17 PM, Pete M said:

is your charcoal canister still hooked up?

Any pics of it? I’ve never personally messed with it so I’m not even sure where it is. Is it that canister below the coolant bottle next to the oil filter? There are 2 very rotted hoses going somewhere but Lord knows what it looks like out of sight. 

[Pete M]

it's the big black cylinder.  need to make sure the lines going all the way back to the tank aren't crushed.  even if you're venting the fumes to air, that's preferable to plugged up.