Gas Caps....some are vented-some aren't???

[ISHOU]

I'm in the early stages of trying to solve the gas fume smell common on our cars. It's on my Gen 1. After searching this forum I want some clarification. Are some gas caps vented and some not? If so, which one do I need? Smell is very strong around filler cap area. I can hear a whistle sound from the tank after shutdown-it goes away when I open the gas cap. New cap installed over 1 year ago(wanted to get rid of locking cap). Thanks for your help.

 

[Rob94]

All gas caps are vented. They allow air in to displace the consumed fuel otherwise you'd build a vacuum in the tank. Sounds like your cap may have issues. Try replacing it.

 

[pjtoledo]

In yes, out no. Gas caps are a one-way deal, they seal fumes in. If your evap emissions system is plugged the tank can become pressurized, not the best of situations.

Perry

 

[nc89sho]

so then after driving, if you open the cap and pressure escapes is that not good? i think every car i have does this.. but i know the 89 does.

 

[MelectroK]

If every car does this? Is there a fix?

 

[Off Road SHO]

The pressure that builds up in the gas tank due to movement cannot be allowed to escape to the air for pollution reasons. All manufacturers run a vent hose to a carbon filled cannister where it is cleaned of the fumes before it is sucked into the engine at the throttle body when the cannister purge valve is open by the computer. I believe that a check engine light will be lit up if this system doen't work properly. One of the checks of our Emmisions Testing procedure here in the Valley is that the one-way flapper valve in the gas cap does indeed allow air to flow in but not out.

Tom

 

[projectSHO89]

There is an article in the FAQs at www.shotimes.com regarding gas smell and the evaporative emissions system.

The 89 has a pretty basic system. Canister, purge valve, and a few hoses.....

Steve

 

[Eric VerValin]

The pressure that builds up in the gas tank due to movement cannot be allowed to escape to the air for pollution reasons. All manufacturers run a vent hose to a carbon filled cannister where it is cleaned of the fumes before it is sucked into the engine at the throttle body when the cannister purge valve is open by the computer. I believe that a check engine light will be lit up if this system doen't work properly. One of the checks of our Emmisions Testing procedure here in the Valley is that the one-way flapper valve in the gas cap does indeed allow air to flow in but not out.

Tom

I know that when the Malibu's cap was not on tight enough, it would cause it to run funny and throw a code for it too. Kinda funny when you take it there, and they said the cap was bad, went to check it and it was just loose. Asked the girlfriend what was up, and she said it was always too tight so she left it loose to get it off easier. Funny it set a code, I thought Chevy was just running out of ways to get my money.. lol

 

[92inPA]

I had the pressurized tank issue last summer. Replacing the purge solenoid fixed the problem for me.

www.rockauto.com has the solenoid for $34. Do a search for Airtex brand, p/n 2N1043.

 

[MelectroK]

Where is the purge sol.

 

[Racer X]

Where is the purge sol.

Follow the smaller vacuum hose off of the throttle body where it goes down in front of the transmission. You'll find the purge valve midway down attached to that line.

 

[MelectroK]

Is that the thingy dangling down there like its not suppose to be there?

 

[Racer X]

Is that the thingy dangling down there like its not suppose to be there?

Yup, that's it.