Dripping Carb on 1925 Buick Master

[dibarlaw]

Need some brain storming on a persistent fuel issue on my 1925 Master. 

 Dripping from carb..... Sometimes ..... Last time overnight over a pint of fuel in the catch can I kept on the floor below the air horn. And the vacuum tank is partially drained. While the engine is running the tank is cycling. I have a visible glass inline filter to verify this.

When shutting down the engine. I have shut off the fuel valve first and waited about a minute until the engine stumbles and then shut off ignition.

 What I have done. 

 All heat has been eliminated from the riser. I made plugs and blanking plates and gaskets. 

Vacuum tank shut off valve was reworked so that it now shuts OFF. 

The male double compression fitting was replaced and is now no longer leaking. 

The main fuel line was replaced since it split where it was turning up from the frame to the vacuum tank.

 The float is a nitrophil one from Gregg Lange. Set 1/8" below main jet.

 Questions:

 Could the tank valve be defective and back cycling directly into the manifold? Residual vacuum still pulling from tank?

 The previous owner's son indicated that they replaced the steel sleeve in the riser. At that time, they also had the vacuum tank rebuilt. At this point I am not sure of the quality of the riser fix. If during operation, is fuel being pulled into the chamber around the inner sleeve? That may contain the volume of fuel found in the catch can.

 Just some straws I am grasping at.

 I would love to walk into my garage and not be greeted by the fragrance of gasoline. 

 

 

[raydurr]

I would suspect a leaky needle and seat in the carburetor. You might start trying to isolate the culprit by running the engine then shutting it off. Then disconnect the vacuum line at the intake manifold and disconnect the fuel line to the carburetor to see if unwanted flow is occurring. Monitor this for a period after shutoff.

I cannot see how the heat riser tube could be a factor in what you are describing.

[carbking]

About 65 years ago, we lived on a farm, and had a pair of John Deere tractors. I ran the newer (1951) model, and Dad used the older (1940) model.

 

Dad told me "ALWAYS shut off the fuel valve, and allow the engine to run out of gas before turning off the key. These tractors have gravity feed to the carburetor, and a spot of dirt will cause the carburetor to leak".

 

One day, came in for lunch, both for me and the tractor, and was in a hurry. Turned off the key, filled the gas tank, and when in for lunch. When I returned from lunch, there was a "wet spot" of approximately 14 gallons of gas under the tractor.

 

My Dad never went to college, but he was one wise man!

 

He said "fill the tank, you can't plow with an empty tank".

 

He then hooked a chain from his tractor to mine, and pulled me away from the wet spot (which more or less dried in a few days), and we went back to the field.

 

NOT ANOTHER WORD WAS SAID ABOUT SHUTTING OFF THE FUEL, AND NONE WAS NEEDED!

 

There was no punishment, except in my mind.

 

I guess 14 gallons of 10 cent gasoline was a pretty cheap lesson!

 

An electrical relay, with an electrical shut-off valve (like is used with dual fuel gasoline/propane systems) wired into the ignition system will prevent the issue.

 

Jon

[garnetkid]

Your carburetor certainly doesn't hold a pint of fuel and you ran it until it was almost empty before shutting it off there there can be two things going on. (1) your fuel shut off valve to the carb from the vacuum tank is faulty and is leaking slowly and (2) your needle and seat needs attention.  I believe the vacuum tank would hold about a pint.

[Grimy]

I've found that marine shut off valves these days have diaphragms that are adversely affected by ethanol.  I look at swap meets for vintage ones that have no diaphragms, simply brass cup-and-cone construction--they seem to last indefinitely or until the mating parts become eroded.

[dibarlaw]

Thanks Jon:

 I can understand if I had not adressed the vacuum tank shut off valve and left it open as to the dripping at the carb from a bad needle valve. Also that I ran the engine with the valve closed untill the carb was dry. My 1925 Buick Standard with the similar set up did this also.

In my frustration with that car I installed an extra ball valve before the carb. 

To garnetkid's response the Vacuum tank holds about 3/4 gallon on the Master.

Edited March 16 by dibarlaw
Added content (see edit history)

[carbking]

I failed to see the "pint" comment.

 

Do you have a cat in the garage using the catch can as a restroom?  The liquid color would be about the same.

 

I would agree with gamekit that the shutoff valve is faulty.

 

Jon

[Roger Barrett]

If you are losing that much fuel you will have to find the leak. Be advised that even if everything else is perfect the porous castings for the float bowls of these carbs are so crude that modern high volatile petrol will seep right through them. Install a shutoff valve at the carburetor.

[carbking]

57 minutes ago, Grimy said:

I've found that marine shut off valves these days have diaphragms that are adversely affected by ethanol.  I look at swap meets for vintage ones that have no diaphragms, simply brass cup-and-cone construction--they seem to last indefinitely or until the mating parts become eroded.

 

The brass ones are still available new; but given the country of origin, the "cone" is probably square!

 

Jon

[dibarlaw]

Jon:

 Here is the new set up I made. Very similar to my Standard set up which has worked fine for about 5 years. I tried to find a valve that would just do a flare or compression fitting to reduce the number of joints that could possibly leak.

Edited March 26 by dibarlaw
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