97 Vacuum In Gas Tank

[tem]

I have never had this happen in any other car that I have ever owned in my life. When I pull up to the gas pump, and unscrew the gas cap, the air rushing past the cap into the gas tank lasts about 5 to 6 seconds. This is really unusual. It is almost acting as if the intale manifold is directly attached to the gas tank.

Any thoughts would be helpful.

Tom

[Thi]

One thing that I can think of is that it has very good seal in the system. As the pump removes the gas from the tank, it creates more vacuum at the cap. Another theory is that the cap's ventilation design is more restricted comparing to other vehicle.

Thi

[SKperformance]

It depends on if you drive the car alot before you unscrew the cap.

If so then it will cause a large mount of vacume as you have such a large tank not taken up with air inside .

It might also be a bad gas cap.

You sure are creating a whole lot of questions on the lx side of things. No problem though as it does just everyone talking. ;)

[roberttran]

I've noticed that on my '99 LX as well. Would it be a good idea to remove the vacuum ever now and then? I would think a vacuum would prevent gas from getting into the engine with ease.

-Robert

[Rookie]

I get the same deal. I would think the seal is supposed to be that way. I believe the major services require that the gas cap gasket be replaced. I've also heard an improper seal can give a check engine light, due to the loss of vacuum - I assume.

Rookie.

[dougjohn]

I've been told that the cap is sealed that way for emissions purposes. In some cases, if your cap is not on tight enough, you'll get a check engine light on your dash -- it's happened to me twice.

The cap is replaced at the major service intervals for that reason -- to keep up with emissions.

So...it's normal. Mine does it too.

...

Doug