The Stovebolt Site Forums The Shop Area Engine Shop Fabled up gas tank ( keg) question.?

I've seen beer kegs used as gas tanks but never looked at the gas caps these folk used. I purchased a 1958 fleetside with a gaston in the bed. It is polished stainless tank as seen on semi trucks. 18 wheelers. It has a 3 inch pipe with pipe trades as a fill It has a screw on 3 inch treated cap ( as used on natural gas pipe ). It has no vent. Does it need a vent or can this heavy dudy tank work ok without a vent. Can a gas tank be a closed system? Thanks for advise.

Short answer- - - - -NO. Once enough fuel is pumped out of the tank to create a slight vacuum, fuel will stop flowing, no matter how powerful the fuel pump is.
Jerry

Thanks Jerry. So the answer / solution is to find a vented gas cap or can I just drill a small hole ( like 1/8 inch) though the pipe cap I have ?

If this tank was on the truck and working when you got it, my guess would be its possible the cap doesn't seal air tight. That being said if you drill a hole in the cap when the tank is full you might get a small amount of leakage from movement of the gas in the tank. Take a look at any lawn equipment that has a vented cap, they have a chambered area that doesn't allow gas to come out.

I'd suggest installing a small compression fitting near the top of the tank or in the cap with a short piece of tubing with a tight 360 degree loop in it. That will allow venting while minimizing splash and dirt/dust contamination.

You need a vent, as high as possible, small and with a dust filter if possible. It can be remote vented with hose or tubing but some way needs to get air into it to replace the liquid that is leaving the tank.

Please note: if you are driving the truck/vehicle infrequently, air in the gas tank will contribute to the (rapid) deterioration of the ethanol fuel in your tank. Everything I've read and my personal experience says the fuel will start to go bad between 1 and 2 months of storage. You can see a post of mine about a month ago showing 3 vials of gas...one new and 2 which had been kept either in a new gas tank or a plastic lawn mower storage tank...and the results are not pretty. So you might not want to vent the thing too greatly. It actually does not take much of a vent to allow a tank to work. You're not consuming fuel like a blown dragster, after all.

Vent includes a small solenoid valve, normally closed. Opens to atmosphere with ignition on.

Thanks everyone. I found a vented cap and adapter at tractor supply company that worked