No Leaks-Then gas everywhere

[oldmanandakid]

While testing the float level setting with a tube type gauge on the Zenith carb in my 30 coupe everything was fine. No leaks, no drips. Several minutes after replacing the plug I returned to find gas leaking everywhere. I rapped on the front of the bowl thinking the float had stuck, checked the plug which appeared tight. It was difficult to see where the major problem was as gas was coming out of the breather and dripping from the bottom.

This was all from the static pressure of the fuel as the engine had not been started or even turned over.

Any suggestions about what I should look for when I tear into the carb tomorrow?

[700rpm]

Do you have the correct plug on the bottom? It has a pipe thread, and the wrong plug will likely strip the threads and cause a leak.

[oldmanandakid]

It was the same plug that was taken out for the gauge installation then easily replaced with no sign of thread damage or cross threading.

[Gary WA]

Gasket?

[Tom Wesenberg]

Also, the gas tank valve should stop any more leaking until you find the cause of this leak.

[oldmanandakid]

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Yep, check and double check on the gasket. Most? of the gas seemed to be coming out of the air intake.

[Mike V. Florida]

Thinking on paper here, Unscrewing the plug drains the bowl and it of course fills up through the valve. What if there is crap in the tank and it clogged the valve or the valve just does not seat correctly? Maybe the reason it does not normally leak is the vibration of the engine makes the valve seat settle better with the weight of the fuel befind it or knocks the crap loose so the valve seats?

[eagle]

Do you have a sinker float? Its easy to find a float with a leak by dropping them in boiling water. The hole will be putting out a stream of bubbles. Although most Zeniths leak past the float valve some. Mine starts dripping gas about 10-15 minutes after I shut off the engine if I forget to shut off the gas.

[columbiA]

The drain plug on an A or B carb is 3/8" NF,not a pipe thread.

[oldmanandakid]

She's up and running with no leaks or drips. Took the carb apart, cleaned, reassembled and even tried the boiled Eagle egg method. I don't have any idea what we did but it now works. It was clean inside and neither the kid nor I could see any gunk that might hold the valve open. It's a mystery but with a good ending. Thanks for the input guys.