jaxcam02

iTrader: (1)

What would cause my filler neck to leak even though the car has been sitting for over six months. I came outside the other day to check on it and noticed excessive buildup of fumes and dirt above and beside the gas tank door. I have no experience with this issue and any help would be appreciated.

RPM WS6

iTrader: (3)

Possibly a marginal seal on the gas cap combined with a hot storage environment that led to vapor build-up/fuel expansion in the tank, thus an overflow. Was the tank very full during this storage period?

I've experienced this exact condition on older cars (meaning non-EVAP or EVAP removed), but can't say I've seen it on a modern vehicle with an intact EVAP system and a gas cap with a healthy seal.

jaxcam02

iTrader: (1)

It has a new cap less than a year old. Less than 10% of the tank full. I last washed the car about 3 months ago and did not notice any excess buildup during the warmer months.

RockinWs6

Some one was stealing your gas?

jaxcam02

iTrader: (1)

Nope it's a locking cap and no signs of tampering. Plus I haven't put gas in it for months

wssix99

iTrader: (5)

It sounds like gas is leaking. This is a common thing with cars...

How do you know it's leaking from the filler neck? Are you saying that you have stains on the floor underneath it?

jaxcam02

iTrader: (1)

No it's a gas (state of matter) or fume leak. The fumes escaping from the fuel door and combining with dirt in the air and building up on the quarter panel above the fuel door.

wssix99

iTrader: (5)

Can you post a picture? This sounds odd - like it's gotta be due to a liquid.

Fumes shouldn't do this. Once gasoline turns to a fume, it shouldn't go back to a liquid. (Unless you are somewhere very very far from Florida.)

jaxcam02

iTrader: (1)

No I'm not saying it was a liquid, but the fumes are obviously escaping and leaving residue on the quarter panel. I guess theoretically it could be the cap itself, but it's less than a year old. I do remember before replacement noticing residue on the quarter panel as well. That's why I replaced it when the car was still my daily driver.

wssix99

iTrader: (5)

If fumes were escaping, you should be getting EVAP codes in the PCM.

I would scan for codes first, then I'd test the gas cap to make certain one can't get it off without the key... If everything comes back clean, I'd clean up the quarter panel and then put a webcam (with motion detection) on the car to see what happens.

RevGTO

iTrader: (12)

If your vent valve solenoid isn't working, then fumes will build up in the tank and then vent the only way they can, through the filler neck. This is happening with my car, and although I don't have grime accumulating around the gas cap, I do smell fumes - especially in warm weather.

What tipped me off to this diagnosis is that the gas pump would keep shutting off during fueling. No codes thrown.

eb110americana

iTrader: (4)

My '98 (metal tank) would leak gas out the filler neck--but only when driving, not parked. Especially when full. Enough that there was gas all down the side of the car. The little flap inside the filler neck was a bit tweaked, but it never leaked before, and it's been like that for over a decade. Supposedly the gas cap failed SMOG, so they put a new one on there (OEM) and it was about a month after that it started leaking. I put another new cap on, and it still leaks. I figured the filler neck, which is part of the tank, was shot. I just took the tank out and tried to dump the last of the fuel out of the neck--go figure, it won't come out.

I think there is some part of the vapor recovery system that is causing excess pressure to build up, which spills fumes and even gas out the filler neck. Mine had a pinched hose near the vapor canister vent valve/solenoid, so that could be it. I am switching to a 99+ plastic tank anyway, so I will probably never know.

wssix99

iTrader: (5)

Right. A physical failure of the valve would not throw a code - only an electrical one.

jaxcam02

iTrader: (1)

Well thanks guys. It seems like I might as well just drop the tank when i throw the heads and cam in this summer. Thankfully I teach so I have all summer to deal with it and throw a new fuel pump in while its all apart