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Thread: Fuel in air cleaners!!

  1. #1
    Senior Member Dusty's Avatar
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    Dec 2012
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    Christchurch, New Zealand
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    Default Fuel in air cleaners!!

    On a recent trip I made a forced landing due to fuel entering entering around the firewall. This may have happened many times previously but I haven't noticed the fuel before .

    At height above 5000 ft (wot 5100-5200, 24-25 manifold pressure) there has always been a fuel smell. Investigation have always found nothing other than fuel staining at the bottom of the air cleaners.

    This time however on landing there was still fuel dripping fron the LH cleaner, the right was damp. We ground ran at wot and couldn't reproduce the leak( @1100 ft) the rest of the trip 8 hrs was at >3000 ft with no problems.

    any ideas?
    Fuel pressure at cruise is 4.8 psi the engine is smooth,EGT's run1500-1400 depending on height and temp,the floats (150 hrs from new are all 3 gr each)
    my float levels are set 1/8 lower than std due to rough running at taxi over rough ground and hot start flooding.

    i have a theory but would appreciate any other suggestions.
    cheers
    Dusty

  2. #2
    Senior Member jrevens's Avatar
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    Arvada, CO
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    Default Re: Fuel in air cleaners!!

    Hi Dusty,

    First of all, what engine do you have? Secondly, are you running your carburetor vent lines into the air filters?
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE

  3. #3
    Senior Member Dusty's Avatar
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    Default Re: Fuel in air cleaners!!

    I am running a new 80 hp ul (150 hrs) my 1993 ul engine had the same issue.
    the vent lines run to the air cleaners with clear tubing that has no sign of fuel staining so I at this stage have eliminated these but can change back to std as an check.
    the air cleaners are the K&N pancake type.

  4. #4
    Senior Member Dusty's Avatar
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    Default Re: Fuel in air cleaners!!

    Problem solved.
    I used foil tape to cover the top 1/3 of the elements, this in theory forces air to be drawn up through the aircleaner causing any fuel accumulating at the bottom to be injested rather than dripping. Today at 6-7500 ft there was no fuel smell. All else remained the same egt manifold pressure etc.

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