Fuel puking out of vent

[threewood]

Tank is a Holley EFI tank, 3/8" feed and 3/8" return from Sniper EFI. There are two vent hoses, one coming off of the fuel pump mount and the other off the body of the tank that go to a Y connector then to the vent. I have the vent mounted as high as I can get it in the rear end tunnel.

Problem is it still pukes fuel occassionally. Today, I filled the tank to 90% capacity, drove home, got under the car. I then opened the gas cap, relieved the pressure built up and the tank started gurgling and spit out some gas from the vent. Non vented gas cap. Sometimes there is no pressure.

Do I need to mimic the factory vent and run a line with a loop in it up into the trunk and back down? That seems like my only option.

 

[Some Car Guy]

I’d at least match the factory. I’m not sure you can avoid this with modern gas. My car has all factory stuff and is routed to the correct nipples on the tank. Still pukes up a bit sometimes when I get home.

 

[The Rebel]

I had the same thing happen to me this spring with the cap locked.

My system is stock, no mods. The tank was full and on days when the air in the garage warmed up as the the gas was cold it expanded and ran out the vent line. As soon as I unlocked the cap it began gurgling. Now l keep the cap unlocked when it's in the garage and it hasn't happened again.

 

[69 GeeTeeX]

I have the same EFI and gas tank with the same problem in a 69' GTX. Only solution I've found is only fill the tank half full.

 

[matthon]

Based on the pic, bring both the tank and sender vent higher into the trunk before joining.

Filling the tank.
I have efi, friend with the same exact car, factory original carburetor.
We both cannot fill the tank completely full, it will puke it out.

Imo, modern pumps don't allow one to modulate the flow, it's all or nothing and the air cannot escape. Whether the gas pump is completely inserted into the fill tube, or slightly less to let air escape, it will puke right before it's full. Seems to do better with the pump in all the way, for some reason.
If I pump it in stages the tank will take more, but in the end it still pukes.

When I go to fill the tank, pop the cap, there is a slight whoosh of air, but I've never had it come out the fill tube after the fact.

Tank full.
I ditched the supplied vent.
Efi tank vent and sender vent connect high up in the trunk.
Tied those 2 into the existing stock vent, which does a large loop in hard line, connects to the top of the fill tube, and drops back down outside the car.

Captain Obvious here, efi constantly pressurizing tank with the return, it helps to have a large loop into the trunk, (that can easily drain on both sides, keep fuel completely out of it).

On my car I was thinking switch to hardline for all vent hoses. No idea, but air is not escaping fast enough, whether stock or efi.

 

[threewood]

Well, I'll run a hardline up into the trunk and back down to see if it helps. I may even try to make the loop a little bigger to get more airspace in the vent. I run 88 clear gas so no ethanol.

 

[kiwigtx]

I ran an external vent in the A100, and it is about 18 inches above the line of the tank, mounted behind the left hand taillight, with a small K&N filter on top.

Works for me. BTW, I am running Sniper with -6AN Supply and Return lines, and a Holley in-tank pump.

 

[Texas97]

i had a different problem. ton of pressure built up in the tank. had "vented" cap on my charger, it wasn't vented good enough. drilled vent hole better, just another bit size up. no more issues

 

[threewood]

Here it goes. 3/8" tubing routed in the stock location. I'll update this thread to let you all know if it works.

 

[Frankb]

That's a Tanksinc tank rebranded Holley. I have same tank in my 68 Charger. I didn't mimic the factory vent and run a line with a loop in it up into the trunk and back down. I ran a line from top vent on tank vent to refuel line in trunk. In Charger there is a nipple in the fuel inlet tube towards the top of the line. On the vent from fuel pump mount i fabricated a metal line and ran it along the drivers side of tank to rear bumper. Im in Tucson and I don't have any vent issues with this setup

 

[matthon]

I ran a line from top vent on tank vent to refuel line in trunk. In Charger there is a nipple in the fuel inlet tube towards the top of the line. On the vent from fuel pump mount i fabricated a metal line and ran it along the drivers side of tank to rear bumper.

How high above the tank does your vent from the fuel pump get?
No worries or issues with fuel siphoning out?

I have a similar setup, except the vents from both the TanksInc tank and sending unit connect to the fuel inlet tube, high to prevent siphoning, (then a loop, then down outside the car).

 

[Frankb]

Id guess about 2 feet. When I max out the tank some fuel will come out of the lower vent. Maybe about a quart is max that ever pissed out. I think this is because some fuel is still in the inlet tube that runs from outside the car to the tank. In this car I can hear when the tank is getting full and if I stop fueling before the inlet tube gets fuel in it then fuel doesn't piss out lower vent tube.

 

[PLUM72]

I am about at this point with fuel venting on my car. I was thinking about running a hardline or hose up through one of the grommets, into a standard fuel filter, then back down under the car. The fuel filter should minimize vapors. I think the right thing is to run the line high up into the trunk and back down

The other idea I saw on a GM forum was to inline a Dorman 80195 filter in the vent line. This is a small carbon filter used inline on the brake booster of a 1980 Corvette.