why is gas coming out of cap?

[kr8zstang]

Twice now i've had gas come out from the gas cap. Once i was at the drag strip with almost a full tank, so i thought it might have just sloshed out. Today it happened again just cruisin around with about 1/2 tank. Anyone got any ideas what might cause this? thanks

 

[vristang]

I would think that it wouldn't take much to slosh fuel up the fill tube.

It may be time to pick up a new fuel cap?

 

[HISSIN50]

Though I dont know how stang tanks are inside, it seems to me that most tanks these days have a reservoir for expansion and overfilling. When the gas filler clicks off, if one continues to top the tank off, it can fill this reservoir.

I'm kinda thinkin that a real full tank coupled with a plugged tank vent could allow some venting of gas out of the cap (tanks are vented, and as an additional safety precaution, gas caps are vented too).

Good luck.

 

[Roland69]

Dont they have baffles to stop fuel from doing that. Maby your baffles have broke loose. That could cause that to happen.

I would check your gas cap and make sure the seal is still good.

That's interesting about the reservoir for expansion and overfilling

 

[HISSIN50]

Dont they have baffles to stop fuel from doing that. Maby your baffles have broke loose. That could cause that to happen.

I would check your gas cap and make sure the seal is still good.

That's interesting about the reservoir for expansion and overfilling

The baffles are for sloshing. But one can continue to fill the tank up with or without baffles.

In the old days, I dont think tanks had this reservoir. But someone decided that if a car overfilled and dumped out the filler, that wasnt cool for the environment so the little reservoir was added.

 

[kr8zstang]

I was going to replace the cap, but when i fuel up, it releases pressure, so i though it is ok. Is this correct thinking?

 

[Shakerhood]

If I am not careful when filling the tank, by the time the handle clicks fuel is already spilling out!

 

[Paully's5.0]

Same thing has happend to my car for about 3 yrs now, I think I've narrowed it down to the canister solenoid valve. I don't believe it is working correctly, not opening and letting the tank vent. I think a new valve is about $30 from napa, gonna finally replace mine come spring.

I get the nice gas smell in the car too!

 

[kr8zstang]

That sounds like it might be the problem. I'll check that out. Yeah, i know it's spewing when i get that wonderful gas smell!

 

[RMODEL65]

the wooshing sound or hissing is the light ends in ur gas escaping they contain octane i belive if my memory serves me correctly! most new cars pressurize the cooling system to check for leaks as part of emissions testing on the car! if it will not hold pressure it trips a check engine light on new cars!not on 5.0 to my knowledege the computer system is not that advanced!

 

[kr8zstang]

whhaattt?

 

[HISSIN50]

RModel is talkin about EVAP systems in OBD-II cars.

For guys with the gas smell in the car, take a look at the purge hose. Mine was rotted at the charcoal cannister and where it goes under the upper intake.
On the 94 it was rotten at the charcoal cannister too. That'll give you a gas smell.

Good luck.

 

[JRPony]

The reason why gas is coming out is because pressure is being built inside the tank and its not being released. When you remove the gas cap, the pressure releases all of a sudden and gas comes out. I've have seen over a gallon spill out out of a gas tank when removing the cap because it was pressurized too much.
You are on the right track with the vent valve. That is most likely your problem.

 

[kr8zstang]

So it sounds like the cap isn't the problem. I'll check out that vent. Thanks for the replies!