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Thread: CC340 - Carburetor Fuel Leak

  1. #1
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    Default CC340 - Carburetor Fuel Leak

    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.

  2. #2
    Senior Member Andy's Avatar
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    Default Re: CC340 - Carburetor Fuel Leak

    Quote Originally Posted by PBY Catalina View Post
    What could be the transient problem that caused this fuel leak?
    Stuck or contaminated carb float valve seems probable.

  3. #3
    Senior Member jmorrical's Avatar
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    Default Re: CC340 - Carburetor Fuel Leak

    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/


    IMG_7724.jpg

    IMG_7722 2.jpg
    Last edited by jmorrical; 01-08-2024 at 07:35 AM.
    Jim Morrical

  4. #4
    Administrator Pete D's Avatar
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    Default Re: CC340 - Carburetor Fuel Leak

    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/
    Pete Dougherty
    Customer Support Manager
    Cub Crafters Inc

  5. #5
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    Default Re: CC340 - Carburetor Fuel Leak

    Quote Originally Posted by Pete D View Post
    ... 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 !

  6. #6
    Senior Member Andy's Avatar
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    Default Re: CC340 - Carburetor Fuel Leak

    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.
    Last edited by Andy; 01-09-2024 at 01:44 PM.

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