kjdavis

Ive got the gas cap light coming on in my 99 GT....seems to be affecting my fuel economy maybe? What is it with these types of caps, is it just the cap that needs to be replaced or could it be something else? Any ideas?

kingC95GT

i think that there is a rubber seal on the cap. and when the car does a evap test and it has a leak down or vaccum problem it will set set a code and or turn the light on. i would check the cap for broken or cracked seals

kjdavis

The seal seams okay. Looks new, no cracks or anything like that, not dried out. Any other ideas that could cause it to throw that code/light?

boduke0220

Mine does that occasionally too.

CircuitBreaker

Did you wash your car recently?? There has been a couple times after washing my car that the gas cap light came on and once it dried out it went off..

kjdavis

Its been on for about a week straight now...

kingC95GT

is there a way to get codes out with out using a scan tool? we did it to my dads 03gt, something with cylcing the key 3 times and something.. anyone know?

jarradasay

disconnect your battery overnite. If it keeps coming on you more then likely have a leak somewhere, hense the reduced gas mileage. It could also be a leak only when the car is warm due to expansion of materials. Look for puddles or drips right after you finish driving. Most people think of the gas cap light as a pain that tells you when you didn't tighten the fuel cap down, but it can be valuable in identifying fuel leaks.
Good luck!

kjdavis

Heres an update of what ive done/checked for.

1. I disconnected the battery for a few hours, and hooked it back up, started the car....and immediatly the light was on. There wasnt even a delay, it was just on.

2. With the car running and up to temperature, I began checking all over the engine; injectors, fuel rail, fuel lines, etc. Checked under the car for damp areas, drips, or puddles. Checked filler neck and around gas tank for leaking....nothing.

3. Hooked up the Superchips to it to pull any codes...nothing.

So can it just be as simple as the gas cap? Do these vented caps ever just suddenly go bad?

One more thing, when you undo the cap and look down the filler, there is a thin metal "flap" which I assume is for splashing and backfilling of the tank to prevent overflow out the neck. If this is damaged in anyway, could that be the problem? Is there a sensor attached to this?

Thanks for all the replies and help!