gas expansion/ leak

[wareaglescott]

Went out for a drive yesterday and filled up on the way home about a mile from the house.
Parked the car. Came out this morning to strong gas smell in the garage and found a small puddle under the right rear tire. Can find no obvious evidence of a leak point.

When I filled up yesterday it got a little fuller than normal. Almost to the top of the filler neck. Got up to about 80 degrees yesterday. Maybe a little warmer in the closed garage. I would assume the gas was quite a bit cooler in the in ground storage tank.

Does it seem reasonable the gas just expanded and came out?
Anyone had this happen?
Would it likely have come out the fuel vent hose?
Other than wiping up any residue I found would anyone recommend any other corrective actions?

Thanks

[wareaglescott]

Update - after posting I thought more about the fuel vent line and went back out and looked. I did the EdwardB charcoal filter in a pvc pipe setup. All my spray paint is eaten off the pvc so it seems pretty clear that is where the fuel came out.

Lesson learned on that one. Dont fill the tank so full or if I do then drive around more after and not straight home to the garage with a super full tank of cool fuel on a warm day.

[shark92651]

It makes sense that if it is going to overflow it would be from your vent hose since that is lower than the filler neck. Looking at the instructions for my Breeze Big Bore Vent Kit, he recommends looping the vent hose as high as possible above the rear PS shock mount, and then back down. I assume this sort of routing, and then perhaps a charcoal filter on the end mounted elsewhere may have prevented this. Perhaps?

[wareaglescott]

It makes sense that if it is going to overflow it would be from your vent hose since that is lower than the filler neck. Looking at the instructions for my Breeze Big Bore Vent Kit, he recommends looping the vent hose as high as possible above the rear PS shock mount, and then back down. I assume this sort of routing, and then perhaps a charcoal filter on the end mounted elsewhere may have prevented this. Perhaps?

I have the Breeze unit also. Mine is mounted high up with the Charcoal filter. Still overcame that. I guess if the volume of the expansion exceeds the volume of your vent hose it is going to come out regardless.

[Railroad]

I will bet I need to relocate my charcoal vent. I am still building, so other than finding a new location, no big deal. Seems like I saw one strapped to the filler neck. Thanks for posting.

[2bking]

I don't have the Breeze vent, jut the one that came with the kit. That said, it has a valve that prevents gas from coming from the tank and only allows air back into the tank as fuel is used. The vent tube is routed to the bottom of the tank in the fender well with the filler tube and without a charcoal filter on it and no high looping. The car sits in the garage with a full tank of fuel and I don't get any fuel smells. I routinely fill mine to the top of the filler tube.

[cgundermann]

I built mine also, but haven’t filled her completely yet. Hopefully it’s not mounted to low, but thanks Scott for sharing - I won’t top her off...

Chris

[mike223]

I noticed last summer if I park the go cart in the sun on a summer day I can watch vapor boiling out of the (clear) vent line.

My tank is painted black.

Working on the trunk aluminum to keep it in the shade.

[mike223]

The vent tube is routed to the bottom of the tank in the fender well with the filler tube and without a charcoal filter on it and no high looping.




Depending on the specifics of your installation...


I've got mine with the Mustang tank vapor valve pointed toward the passenger side, looping up (further toward PS) and then back down toward the drivers side.


On three different FFR roadsters - this routing has been required to prevent spewing fuel in autocross left hand corners.


All other attempted routings would intermittently spew noticeable amounts of fuel in a hard left hand corner.



I tend to think the charcoal filter is counter productive (just another place for fuel to gather).

[wareaglescott]

I don't have the Breeze vent, jut the one that came with the kit. That said, it has a valve that prevents gas from coming from the tank and only allows air back into the tank as fuel is used. The vent tube is routed to the bottom of the tank in the fender well with the filler tube and without a charcoal filter on it and no high looping. The car sits in the garage with a full tank of fuel and I don't get any fuel smells. I routinely fill mine to the top of the filler tube.

Interesting King. Thanks
My filter is next to the filler tube. Mounted on the side of the panel.

https://thefactoryfiveforum.com/attachment.php?attachmentid=57344&d=1470864650

The scotch bite pads and charcoal were definitely full of fuel. When I reached up and unhooked it and and tipped it upside down to detach it more fuel dripped out so I am for sure that is where it came from. There was no longer any fuel in the hose just the residual that had soaked into the pads. I wonder if my Breeze piece was supposed to keep fuel from entering it? If something allows air/vapors out how can it not also let liquid out in an over capacity situation?
I am quite surprised the fuel expanded that much.
Is there any other possible explanation for how fuel could end up in that hose?

[wareaglescott]

I built mine also, but haven’t filled her completely yet. Hopefully it’s not mounted to low, but thanks Scott for sharing - I won’t top her off...

Chris


I will say I fill it up that much pretty much every time. I keep a fuel mileage log so I can tell you that is the 20th time I have filled it up. Never had an issue before. Pretty confident I have filled it numerous times at the exact same station and driven directly home. Maybe just the fact that it has been cold and considerably warmer yesterday created the perfect storm for expansion. I am really not sure. Did surprise me though.

[wareaglescott]

I tend to think the charcoal filter is counter productive (just another place for fuel to gather).

That could be the case as well. In my case I have about 3' of tubing before it even gets to the charcoal. Takes a decent volume of liquid before it would ever get there. I have never had a gas smell before so maybe it works. I am glad to have it. With that said I have never had a Cobra without a filter so I wouldn't know if that works just as well also.

[mike223]

I wonder if my Breeze piece was supposed to keep fuel from entering it? If something allows air/vapors out how can it not also let liquid out in an over capacity situation?



The primary function of those valves is to prevent the gas tank from emptying through the vent tube in a rollover crash.

The valves are not "perfect", they all can certainly spew liquid fuel in an autocross situation.





I am quite surprised the fuel expanded that much.



I suspect the fuel did a little boiling / vaporization - one pound of liquid gasoline produces about 3.2 cubic feet of vapor (23.94 gallons of vapor at sea level).

[RoadRacer]

I was curious how much it expands, and found this:

"So, at 60oF, a normal gallon of fuel will occupy 231 cubic inches of space, but that same gallon at 80oF would expand to 233.7 cubic inches, and at a colder 40oF, would contract or “shrink” to 228.3 cubic inches."

https://desertfuels.com/industry-education/gross-vs-net-when-is-a-gallon-not-a-gallon/

So, 13 gallons = 2967 cubic inches at 40deg, 3038 at 80deg - a difference of 70 cubic inches (or 0.3 gallons expansion).

[wareaglescott]

I was curious how much it expands, and found this:

"So, at 60oF, a normal gallon of fuel will occupy 231 cubic inches of space, but that same gallon at 80oF would expand to 233.7 cubic inches, and at a colder 40oF, would contract or “shrink” to 228.3 cubic inches."

https://desertfuels.com/industry-education/gross-vs-net-when-is-a-gallon-not-a-gallon/

So, 13 gallons = 2967 cubic inches at 40deg, 3038 at 80deg - a difference of 70 cubic inches (or 0.3 gallons expansion).

Interesting so worst case we are about 38 ounces. I cant imagine my starting temp was any lower than 60 so 19 ounces maybe in my case. Hard to quantify how much I had on the ground but it wasn't a ton. Surprised I was full enough that I had overflow.

Could this possibly be explained by something other than expansion? Do I have some other issue?

[FLPBFoot]

Another way to say this is for Gasoline there is about a 1.17% change in volume for every 19F degree change in temperature. Depending on how cold the gas was when it went into your tank it can expand a bit. It is not uncommon for gas coming out of an underground tank to be at 50 degrees. You come home and it sits in your 80 degree garage overnight it will expand by 1.85% 13 gallons @ 50F degrees becomes 13.25 gallons @ 80F degrees. If you filled it really full you could get it to overflow. I think typically a fill up would allow for the added volume change but get it full and an overflow is possible.

[mike223]

Could this possibly be explained by something other than expansion? Do I have some other issue?




Yes - primarily the butane content of winter gasoline blends.

[mtcoriel]

37 years as a refinery worker. Gasoline is blended with more light ends in the winter than in the summer for easier starting.

[Frank Messina]

This seems to be a common problem. Not sure why but the fittings on the top of these tanks are not leak proof. I finally smartened up after the second episode of a fill up (over filled) on a blistering hot day. Parked in the garage and had gas coming out the fuel level sender. Now I fill up on the way out and only put in what I think it takes to get it close. If the pump clicks off, that's it I quit right there. A 20 - 30 mile drive will lower that level enough to thwart any leakage.
Frank

[GFX2043mtu]

If it's only leaking at your charcoal canister you you can either raise it as high as it can go or install a fuel cell discriminator valve to keep the fuel in when the tank is full and it try's to slosh out.

[wareaglescott]

If it's only leaking at your charcoal canister you you can either raise it as high as it can go or install a fuel cell discriminator valve to keep the fuel in when the tank is full and it try's to slosh out.

Didn't slosh out from driving I dont believe. The car was parked for multiple hours before the temp went up and it expanded.