Gas goes in very slowly

[Deleted User]

A few years ago I made some rust repair to my '51 Pacemaker tank and applied a Hirsch sealer. Since then mostly I've been working on the car, with just a few gallons poured in from a can. Earlier this week I finally drove to a gas station for a real fillup. There were probably 5 gallons already in the tank. After about 4 gallons, the filler pipe overflowed. I spent a few minutes coaxing a little more in, but finally drove home and returned with my 5g can. At home, pouring that 5g in took about 25 minutes. Not fun to think about having to do that on a tour or long trip.

The vent tube (the tube from the top of the tank to near the upper end of the filler pipe) is clear. All I can think is that maybe the sealer plugged some of the passages between sections of the tank. As I recall, though, from when I was doing the work, there's really only one baffle that divides the tank in half, and I'm pretty sure the overflow started when the tank was less than half full.

Any suggestions... hopefully that do not involve removing and opening up the tank again!? 

Glowplug

The vent tube is connected to the tank through a valve that acts like a burp valve. If the valve is incorrectly functioning it can act as a siphon and will fill the filler tube versus allowing the tank to fill. Been there done that... used the same sealer too.

bob ward

I never knew there is a valve in the stepdown vent tube arrangement. 

I always thought the stepdown was a PITA to fill because of the fill pipe configuration. That is, because the filler pipe enters the tank at the bottom (rather than the top) the fuel is trying to flow into the bottom of the tank through the fuel that is already in the tank. 

Please tell me more.

Glowplug

See the pictures...the tube is connected to a burp valve which allows air being compressed by in coming gasoline to escape from the tank. Gas entering at the bottom of the tank pushing air out will fill without backing up into the fill tube. Crushed rubber hose at the frame is the usual reason for air NOT escaping from the tank. Tank sealant can cause the burp valve to stick. Hope this helps.

[Deleted User]

What's the fix? Anything that can be done without dropping the tank?

Glowplug

What's the fix? Anything that can be done without dropping the tank?

Nothing I know.

[Deleted User]

What's the purpose of the valve? Wouldn't just an un-valved vent tube do the same thing?

bob ward

The valve is presumably some sort of float or flap that gets closed when the tank is full? Anyone have one out of a tank they can take a photo of?

I'm a little puzzled as to why a valve was needed in the vent tube, but Hudson installed several 100 thousand of them so they obviously thought it was necessary.

Maybe, and this is in the days before auto cut-off fuel pumps, it was a means of letting you know your tank was nearly full before you got fuel all over your shoes?

Glowplug

The only time I ever had one of these valves out was when I cut up a rusty tank.  Years ago.   The valve is mean to allow the air to come out and the gas to stay in. A stuck valve keeps the air in the tank and if that is so, the gas has no place to go except back out the filler tube.  

A modern example and explaination of the valve purpose can be read here;

http://www.autopartswarehouse.com/fuel_tank_vent_valve~pop.html

[Deleted User]

Thanks, Farmer. I have a parts tank but that valve is welded in. Since I do not see any reason to prevent gas from splashing back up into the vent tube, an unlikely event anyway, I guess I'll try to defeat the valve action. Not sure how, but that's the plan at present.

EDIT: Aah... just noticed your link. Interesting, but relevant to old open systems like ours?

[Deleted User]

New problem, probably related: After essentially force-feeding another 5g into the tank, it showed about 3/4 full on the gas gauge. I started the motor and went out to look at it. Gas was pouring out of the carb, onto the heat shield. Shut down, sop up...

Thinking the mostly-full tank and clogged valve might have caused excessive fuel pressure, I siphoned out about 9g. The tank then read 3/8 full, but starting the motor gave the same result. Maybe it's bench time for the carb. Not sure I have another kit.

Anyone see a logical connection between almost-filling the clogged-vent tank and the carb leak? All I've got it the pressure theory. Before my attempt to fill the tank the carb did not leak, especially pouring out as it does.

RL Chilton

" I siphoned out about 9g . . ."

For future reference, if it is not damaged, there is a drain plug in the front left hand side of your tank, which makes removing gas MUCH easier.

I think you have a carburetor/float issue.  

[Deleted User]

Thanks, Russell... but I tried to remove that drain plug a few years ago when I was working on the tank (it was out of the car, dry and clean) and was unable to budge it. Tried some pretty long extension bars, etc., but did not want to tear the tank. So as far as I'm concerned that drain plug does not exist

dwardo99

I agree that the carb overflow is not related to the tank. Either a float/needle issue or too high fuel pressure from the pump. I have had the same problem with pumping gas into either my Hornet or my Wasp, I don't remember, but the solution was to straighten out a kink in the hose. I only have a vague recollection of it but I don't remember dropping the tank to fix it. Once the kink was gone from the hose, it took gas like anything. Hudsons like gas, lol.