Random Carburetor dripping seeping drooling

Jim Isaacs wrote:

So riddle me this folks- if leaving one’s fuel shutoff valve open on a high wing aircraft when parked overnight can possibly override a carb float bowl fill valve-which is designed to function under 5.8 psi continuous pressure-and create a fuel leak- how could this occur when my fuel pressure gauge indicates 0.7 psi static fuel pressure to the carbs under said circumstances? 
I could agree with a small particle of debris lodged between the float bowl valve tip and seat causing such a leak, but not 0.7 psi of constant pressure. 
On a side note, when I was inspecting things the day I found the leak, when I removed the air filter I found fuel seeping from both the idle air valve and the needle jet air duct at the air filter opening. Looking at the Bing diagram in the MMH, I don’t see any common intersection of these air passages. Hmmm. Anyway, as of this morning, all is dry and well.

This oozing of fuel from a high wing with the shut off valve left open isn't as rare as you may think. With constant head pressure fuel can ooze past the viton tipped needle valve.  Over the hours it will fill the carb bowl and eventually leak out of the carb.

I've seen this many times. The best practice for any high wing is to always shut off the fuel. 

Now sometimes this oozing fuel can be helped by replacing the needle valve or polishing the needle valve brass seat. The other thing that can help at times is checking to measurement on the brass float armature to make sure it is at its proper height at 10.5mm. Then it may not be any one thing, but a combination of these. 

Leaving the high wing fuel valve on and allowing the carb to flood makes starts harder and rougher.

Just checking back in with an update- it’s been almost three months and several flights with no recurrence- no drips, no leaks, fuel valve always on, five gallons of fuel in each tank. 

Jim Isaacs wrote:

Just checking back in with an update- it’s been almost three months and several flights with no recurrence- no drips, no leaks, fuel valve always on, five gallons of fuel in each tank. 

So what do you think fixed it?

I suspect that a tiny piece of debris prevented the float needle valve from sealing, and when I dropped the carb bowl to investigate what was going on, it flushed away along with the fuel that drops when the float needle quickly dropped as I lowered the bowl. This is my theory because I really didn’t do anything other than clean and inspect the float bowl, float needle valve, weigh the floats, and reassemble. Next month is my five year in service rubber replacement anyway- I’m planning on sending the carbs off to someone who does them for a living.