CC340 - Carburetor Fuel Leak

[PBY Catalina]

Hello everyone,


I now have about 75 hours of flight time on my EX2 and everything is going well. I enjoy beautiful weekly flights in the Italian Alps.


I had a small technical problem this week about which I'd like to get your opinion.


Usually, I park my plane in the hangar with the fuel selector closed and leave the mixture on "cut-off". When I go flying, I open my fuel selector to "both" and start my external. This week, after opening the fuel selector, fuel began to flow severely from under the carburetor. The leak worsened when I moved the mixture back to full-rich, and stopped when I put the fuel selector back to off. The leak occurred 3 times and then stopped.


I opened everything, checked all the drains and opened the gascolator; there wasn't the slightest trace of dirt in the fuel. The leak has not recurred.


What could be the transient problem that caused this fuel leak?


Thank you for your help and best wishes for 2024!

Y.

[Andy]

What could be the transient problem that caused this fuel leak?

Stuck or contaminated carb float valve seems probable.

[jmorrical]

Yves,

I assume you have the AVStar LVC-5-4PA carburetor like I have on my CC340. I would suggest you contact AVStar. I spoke to Rene and he was very helpful even for my simple leak. I just needed advice and a course for correction.

I have just completed 10 hours flying my EX(1). I was very disappointed to see a fuel leak at the Bowl Drain Plug at the back of my carburetor!

You can find technical publications on their website. At the Contact Us tab you can find phone #s or a place to fill in the blanks to send a message.

https://www.avstardirect.com/


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[Pete D]

Hi Yves,

That sounds like a float stuck, sometimes tapping on the side of the carburetor can dislodge it, but it shouldn't do that. I would follow Jim's suggestion to reach out to Avstar on this. They are in Florida, USA but do have facilities in Switzerland and the UK as well.

https://www.avstardirect.com/contact-us/

[PBY Catalina]

... I would follow Jim's suggestion to reach out to Avstar on this. ..
https://www.avstardirect.com/contact-us/

Tks Pete ! I'm calling them !

[Andy]

Model LVC-5-4PA claims to have increased float clearance to prevent float sticking. Float sticking due to insufficent clearance had resulted in a service bulletin for earlier carbs.

https://www.avstardirect.com/av10-61...pa-carburetor/

https://www.avstardirect.com/content...2%201-8-19.pdf

My vote is still contamination of the float valve. I'm reasonably confident that the excessive rich mixture I had with my AVStar fuel injection servo was caused by contamination left over from manufacturing.

It's experimental. I'd open the carb, inspect, and blow out all the fuel passages with compressed air.