High Pressure in Gas Tank

[lgvl]

I noticed the last time i filled up after a longish trip, 70 miles or so, that when i took the gas cap off there was a lot of pressure in the gas tank. So much pressure in fact that it was pushing the gas cap off and you could hear the gases coming out as i unscrewed the cap. Any suggestions? Just to add it was a pretty hot day, 80 degrees or so. Thanks!

[76stepsidechevy]

You probably have a vent line clogged or pinched off somewhere or a sealed cap where there should be a vented one. The return/vent line in my sending unit was plugged solid with rust or who knows what. I drilled a small hole in an old gas cap until I had the time to change the sending unit.

[lgvl]

So i took my bed off to undercoat the rear of the frame and decided to snap a shot of the sender unit to try to figure out why my gas tank pressure is so high. I'm guessing the bolt is not supposed to screwed into the middle tube?

[ray_mcavoy]

Looks like you found the problem! That middle tube is the gas tank vent and definitely shouldn't be plugged.

It would have originally run to a charcoal vapor recovery canister under the hood (for trucks considered "light duty" by emissions standards for that year). Or would have been capped off with a plastic breather cap like you'd find on an axle or transmission (for trucks considered "heavy duty" by emissions standards).

[lgvl]

Originally Posted by ray_mcavoy

Looks like you found the problem! That middle tube is the gas tank vent and definitely shouldn't be plugged.

It would have originally run to a charcoal vapor recovery canister under the hood (for trucks considered "light duty" by emissions standards for that year). Or would have been capped off with a plastic breather cap like you'd find on an axle or transmission (for trucks considered "heavy duty" by emissions standards).

Ahh, i had thought of an axle breather cap as a replacement as well. Too bad i had to put the bed back on already. Guess i will be dropping the gas tanks. The truck has dual tanks with both vent hoses plugged, can i get away with putting a breather on one tank and leaving the other with the plug in? The two tanks are connected and equalized.

Thanks!

[anubisani]

Originally Posted by lgvl

Ahh, i had thought of an axle breather cap as a replacement as well. Too bad i had to put the bed back on already. Guess i will be dropping the gas tanks. The truck has dual tanks with both vent hoses plugged, can i get away with putting a breather on one tank and leaving the other with the plug in? The two tanks are connected and equalized.

Thanks!

is it possible u cld just chg to a vented gas cap