Gas Tank Pressure

[Tuggertim]

Hello All,
I noticed that my gas tank has a massive amount of pressure when I remove the gas cap. Also, the car is running extremely rich, but cranks and drives fine. I saw that there is a two way valve in the vapor vent line to the tank, could this be the culprit? Or, is this normal to the car? Does anyone have a part number for a fuel filter? My local parts stores are have a bit of trouble looking up my car. 1984 Pininfarnia Spider Any help is much appreciated!

Thanks,
Tim
Pensacola, FL

[RRoller123]

Is it pressure as in positive pressure OUT? Or vacuum pulling IN?

[Tuggertim]

Positive pressure out, it actually blows the cap off at the last thread then continues to vent.

[RRoller123]

Very odd. I have no clue on this.

[BEEK]

you have a blockage in the gastank /evaporative system

[RRoller123]

Shouldn't that create a vacuum?

[djape1977]

whatever is the cause, vacuum or pressure, breather hose is blocked

[RRoller123]

Just curious, how does that pressurize the gas tank?

[rlux4]

Gasoline evaporates, and without venting the gas (vapor) builds up. You've probably seen this with gas containers, especially in the summer. Without a vent cap left open they can puff up pretty good.
Ron

[Tuggertim]

Many Thanks, I will check it out this weekend.

Tim

[majicwrench]

I have seen a lot of cars with pressure in the tank. Not saying everyting is OK, just lettin you know that a certain amount is normal.
Keith

[RRoller123]

So evaporation due to temperature rise would raise the vapor pressure in the tank. That makes sense. Then the Evap Control system should relieve that, through the charcoal canister, therefore it seems likely that there is a blockage in that system, as was originally suggested.