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Thread: Clogged Fuel Tank Quick Drain?

  1. #1
    Captain Ron's Avatar
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    Clogged Fuel Tank Quick Drain?

    Went to sump the tanks this morning and could barely get a slow drip from the left tank. I'm used to these things leaking so this was a bit of a surprise. I'm assuming it must be gunked-up but is it possible that the o-ring can swell to cover the outlet? And, yes, there was fuel in the tank (fresh last week) .

    Cheers,

    Jeff

  2. #2
    8GCBC's Avatar
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    In my experience a clogged drain is a sign of fuel tank damage or deteriorating. If you are sure the fuel is clean then, the debris is from the tank.

    How is the gascolator screen?
    Last edited by 8GCBC; 09-13-2020 at 09:40 AM.
    2018 R44
    IA/A&P, ATP, SES, CFII, MEI, Rotor PPL (2500 TT)
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  3. #3
    skywagon8a's Avatar
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    Quote Originally Posted by Captain Ron View Post
    Went to sump the tanks this morning and could barely get a slow drip from the left tank. I'm used to these things leaking so this was a bit of a surprise. I'm assuming it must be gunked-up but is it possible that the o-ring can swell to cover the outlet? And, yes, there was fuel in the tank (fresh last week) .

    Cheers,

    Jeff
    You haven't said what type of airplane. Turn the main fuel selector so that only the the left tank can feed the sump on the firewall. Open the gascolator quick drain. Do you get a strong flow? If yes, your tank drain has a restriction. Get a plug of the same thread, remove the drain valve and fix it. If no, there may be a restriction on the finger screen in the tank. Usually this is not likely as it would take a lot of contamination in the tank for this to happen.
    N1PA
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  4. #4
    www.SkupTech.com mike mcs repair's Avatar
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    Temperature?? Ice/slush?


    Sent from my iPhone using SuperCub.Org

  5. #5
    Richgj3's Avatar
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    Quote Originally Posted by 8GCBC View Post
    In my experience a clogged drain is a sign of fuel tank damage or deteriorating. If you are sure the fuel is clean then, the debris is from the tank.

    How is the gas collator screen?
    Some of the early Legend Cubs left the factory with small bits of aluminum in the tank from machining. The only symptom was clogged drains. I think there was a service bulletin. I would take the drain out and see what comes out in addition to gas.

    Rich
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  6. #6
    Captain Ron's Avatar
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    Thanks guys. It is an Experimental PA-18. I had good flow at the gascolator quick drain but will check the screen when I check the tank drain.

    Question though - would good fuel flow at the gascolator actually prove that the restriction was only in the tank quick drain? In my head I think you'd have to have the header tank drained before the flow from the gascolator would slow.

    Cheers,

    Jeff
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  7. #7
    Captain Ron's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Temperature?? Ice/slush?
    Thankfully that's not a possibility yet! Was a sunny 75F at the time.
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  8. #8
    cubdriver2's Avatar
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    Mud dauber? Take a 1/8 " twist drill and spin it up into the drain while holding the bit in your fingers

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  9. #9
    BC12D-4-85's Avatar
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    Header tanks are vented so can flow their contents then slow if feeder main has flow issues. If you suspect debris in main drain it down some then rock the wings to force remaining sloshing fuel to maybe dislodge crap on the outlet finger filter and in tank. Drain the main with quick drain removed and look for debris. Use a 1/8" pipe nipple to hose into a bucket to reduce static fire from falling fuel. Then run fresh fuel into main and out still open drain to flush. Clean the quick drain and fuel cap vents (spiders like cap vents) and reinstall. My way but there may be others.

    Gary
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  10. #10
    irishfield's Avatar
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    Skip the guess work... take 45 seconds and thread the thing out and look at it. Use your thumb.. on and off the hole and see what comes out. Have the appropriate 1/8 or 1/4 NPT plug to stick in the hold while you inspect the drain.

    This is all of course after you do what Cubdriver suggested and clean the drain fitting with a bit first!
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  11. #11

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    found mine clogged by a rag after a full rebuild about 15 years back.I was not impressed!
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  12. #12
    Captain Ron's Avatar
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    Quote Originally Posted by irishfield View Post
    Skip the guess work... take 45 seconds and thread the thing out and look at it. Use your thumb.. on and off the hole and see what comes out. Have the appropriate 1/8 or 1/4 NPT plug to stick in the hold while you inspect the drain.

    This is all of course after you do what Cubdriver suggested and clean the drain fitting with a bit first!
    That's the plan (+ checking the gascolator screen). I have a spare quick drains for rapid changes when the o-ring leaks so I'll swap it out and inspect. If there's evidence of crud in the tank we'll move on to more serious draining, etc.

    Cheers,

    Jeff
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  13. #13

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    Any time drain clogged, it's been a mud fly/wasp. Small finishing nail does the trick.
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