Gas tank vent

[Jack Duncan]

Where does the smaller vent hose connect, to the larger one? My plan is to install a check valve in the larger vent hose just in case (God forbid!) I got upside down. Also, why don't I also install a charcoal filter in the line so I won't be smelling gas fumes in the garage?

[Bryan Porter]

Don't over think it
the tiny hose I just plug it
the one next to the filler tees back
into the filler as close to the cap as possible

[Don]

Do you have a picture of what you are talking about? My tank has 3 connections; one is the main fill, right next to it is about a 1/2" vent, then there is a very small pipe on the opposite side of the tank which was the fuel return for fuel injected cars. I plugged that one with JB Weld.

On a Beetle, the 1/2"(?) vent connected back to the fill pipe above where the gas station nozzle would be sticking when you are filling the tank. That gives the air in the tank somewhere to go when you are filling and prevents the glug-glug. If you are filling your tank motorcycle style, you dont need that vent so I plugged that one as well. You do need a vented gas cap so that air can enter the tank as fuel is being drawn out by the fuel pump and to allow the tank to "breathe" with changes in atmospheric pressure/temperature.

[CoryN]

What if you do not have a stock filler?

My tank has a relocated tube dead center. Just a tube welded on. I'll connect it to my aero style gas cap via a fuel filler hose.

What does it need for venting purposes? How big etc?

Could I tap into the tube and run a small hose to the bottom of the car, something similar to how you would tap into a house pipe to run water to say a refrigerator or something?

[mike cook]

you just need a small vent line like 1/8" I just welded a nipple into the filler neck then just put a couple of loops in the hose then ran it out a hole in body!! you could JB weld it in if your using a used tank the loops keep fuel from sloshing out and just lets air escape

[Don]

Cory,

If your fill hose goes straight down from the gas cap to the tank nozzle then I don't think you need any vent except a vented cap. The diameter of the tank nozzle is much larger than that of a gas station hose nozzle so there is plenty of room for fill venting in the annular space. Just like filling a lawn mower, you just stick the nozzle into a larger hole and go. Now if your gas cap is designed so than the gas station nozzle fits into it tightly then you will need to do something else. What you want to avoid is having a large vent that's open to the atmosphere all the time because that just lets a lot of gas evaporate and makes your garage stink. I doubt if 1/8" would be large enough for fill venting especially since the VW vent is about 1/2"

[mike cook]

If you look at the older necks on stock VW tanks they are indeed !/8" and is what I used on mine with no problem at all the larger vent ;lines were on newer Vw where they had to meet epa standards and had charcoal canister and some had fuel injection and had return lines I agree that a vented cap would do the trick but if you can't find one to fit your neck then the vent line is needed

[David O']

The 1/2 inch line was to allow air to escape into the fill neck when putting gas in the tank. The 1/8 line was to keep the tank from building pressure when it gets hot in the weather. All of the stock gas caps used on the tanks are vented caps. The charcole canaster system was to allow the engine to burn the fumes when the car was started....EPA stuff to control the hydrocarbons from getting into the air.

[Jack Duncan]

Boy, I really started something when I asked this question. Since I posted my question, I have purchased a charcoal canister and roll-over check valve. To just tie the 1/2" vent hose back into the filler neck, I would have to now try to install a nipple in my new Cool Cap (The one that opens with a key.) which had to be shortened to fit the 90 degree hose. My new cap has a rubber O-ring and is not vented. It's very simple to run a hose from the vent to a point above the filler neck, through the check valve then back down to the canister, then overboard. I'll plug the small vent on the opposite side. Does this sound like overkill?

[Bryan Porter]

sounds good to me