Primer stuck when cold (C172)

Discussion in 'Maintenance Bay' started by Pedals2Paddles, Jan 2, 2015.

  1. Pedals2Paddles

    Pedals2Paddles Cleared for Takeoff

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    When it was warm, the primer on our 172 was smooth as silk. I noticed as the temperature has been falling, the primer was getting more and more difficult to operate. Today it was 30 degrees and completely stuck. I could twist it to unlock with difficulty. And it would not pull out at all. Pull any harder and it would have ripped off the panel.

    What can I do about this?
     
  2. poadeleted20

    poadeleted20 Deleted

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    Lube the O-rings on the plunger shaft. Ask your friendly local mechanic for some "fuel lube" and to show you how to pull the plunger out, clean it, lube it, and put it back together. Then get a tube yourself so you can do it solo next time.
    http://www.aircraftspruce.com/catalog/cspages/ezturnlube.php
     
  3. BigBadLou

    BigBadLou Final Approach

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    Ron is right, the O-rings are dry and probably also aged. If you open it up and the O-rings are in a bad shape, have the mechanic replace the O-rings because it is just a matter of time before they fail and fuel starts pouring into your cockpit. :hairraise:
    (BTDT)
    Depending on the price of the FAA-certified gold-plated unobtanium-made O-rings, it might be enough to buy your A&P a lunch. Or possibly a new Mercedes. :lol:
     
  4. poadeleted20

    poadeleted20 Deleted

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    If Lou's right and the O-rings are shot, your mechanic probably has a box full of O-rings to fit. But after you remove the old ones and put on the new ones, make sure you lube it before replacing the plunger, and make it routine to re-lube them every time there's the slightest feeling of less than smooth operation.

    BTW, you can get spare primer O-rings from Aircraft Spruce, but at $5 plus shipping for the pair, they're probably cheaper from your friendly local mechanic. ;)
     
  5. BigBadLou

    BigBadLou Final Approach

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    So no new Mercedes for the mechanic? He can't catch a break! :)
     
  6. Pedals2Paddles

    Pedals2Paddles Cleared for Takeoff

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    Thanks guys. I was lubed at annual a month ago, and working great, but also about 20 degrees warmer. Seems odd that it is now immovable already, but now I know what to do about it. Lack of lube does it to me all the time!

    How does one remove the plunger to do this? Also, won't fuel come pouring out into the cockpit when I remove it? Should I shut the fuel off and run the engine until it stops to prevent that, or am I over thinking this?
     
  7. Tom-D

    Tom-D Taxi to Parking

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    I'd like to see any one show me where an owner can remove components of a fuel system.
     
  8. Pedals2Paddles

    Pedals2Paddles Cleared for Takeoff

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    I remove the fuel tank caps all the time. That's a component of the fuel system. Better tell the forum lawyers.
     
  9. Tom-D

    Tom-D Taxi to Parking

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    Things that are made for servicing are not maintenance, pulling the plunger out of fuel pump is.
     
  10. Pedals2Paddles

    Pedals2Paddles Cleared for Takeoff

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  11. poadeleted20

    poadeleted20 Deleted

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    It's a matter of touch, so you get your mechanic to demonstrate the first time so you can do it yourself thereafter.
    Not pouring, but you can spill a little if you aren't careful.
    Yes, you are.
     
  12. poadeleted20

    poadeleted20 Deleted

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    See item #6 in preventive maintenance, quoted above, and note the lack of any restriction regarding primers. Unless, of course, you think the primer plunger isn't "nonstructural".
     
  13. poadeleted20

    poadeleted20 Deleted

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    Actually, lubing the primer plunger is "preventive maintenance" (see item #6 in the PM list), so by regulatory definition, it is not "maintenance":
    Of course, digging into the fuel pump would be quite another story, but that's not where the primer plunger is in any plane I know.
     
    Last edited: Jan 2, 2015
  14. Dan Thomas

    Dan Thomas Final Approach

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    When I maintained a fleet of school airplanes, I tried using Fuel Lube on the primer O-rings. The primer just got sticky a lot sooner and gave me far more trouble. I finally just thoroughly cleaned the primer bore, put on new O-rings (MS29513-012) and assembled it without any lubrication. The fuel itself is all the lube it needs, and after that I had very few primer issues.

    Fuel Lube is made for fuel valves (the metal-to-metal plug type) and for gaskets. There's something in it that causes issues with the o-ring material, and the crud I cleaned out of primer bores that had Fuel Lube in them was black, and the O-rings were worn out.

    Dan
     
  15. Pedals2Paddles

    Pedals2Paddles Cleared for Takeoff

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    Interesting. Sounds kind of similar to people who grease flap tracks and act surprised when it is full of crap a few days later.
     
  16. Tom-D

    Tom-D Taxi to Parking

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    IOWs you don't know the primer pump, is a pump.

    You can lubricate any thing on the aircraft, even when it requires a removal of a cover.

    the first sentence gives it away.
    (6) Lubrication not requiring disassembly other than removal of nonstructural items such as cover plates, cowlings, and fairings.
     
    Last edited: Jan 2, 2015
  17. Tom-D

    Tom-D Taxi to Parking

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    What you do to lubricate the plunger is to remove it, that's called disassembly, and that plunger is not a cover, panel or any other thing you as an owner are allowed to do as Preventive maintenance.

    A pump is any device that is meant to move a substance when operated. that is exactly what a primer pump does, it has inlet and out let check valves and a single piston, which you remove when you lubricate it.
     
  18. poadeleted20

    poadeleted20 Deleted

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    You'll have to excuse my confusion -- in 45 years in aviation, you are the only person I've ever seen call a panel-mounted plunger primer a "fuel pump", which is a term I've never heard applied to anything other than those electrical/mechanical pumps, never a plunger primer. In any event, your post appeared to suggest that lubing the primer plunger O-rings was "maintenance", which a pilot cannot do alone, rather than "preventive maintenance", which a pilot can do legally without a mechanic to supervise/sign, and that's an important distinction.
     
  19. Tom-D

    Tom-D Taxi to Parking

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    The most frequent problem is getting the fuel lube in the out let check valve. then the whole thing quits
     
  20. Tom-D

    Tom-D Taxi to Parking

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    I would guess that is why you are a CFI and I am a A&P-IA.
     
  21. poadeleted20

    poadeleted20 Deleted

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    That's an interesting opinion, but I don't think it's shared by the FAA.
    Unless you think replacing the primer plunger O-rings is a "complex assembly operation" -- and I don't think it is. And I think those O-rings do qualify as "small standard parts".
     
  22. poadeleted20

    poadeleted20 Deleted

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    That's right -- I'm the one trained, certified, and authorized to teach pilots the privileges and limitations of their certificates, and that's what we're talking about here.
     
  23. tmyers

    tmyers En-Route

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    You two need to just get a room and get the sex over with.
     
  24. Tom-D

    Tom-D Taxi to Parking

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    If you are teaching maintenance you are in over your head.

    here is what a pump is and a pretty good description of a primer pump.
     

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  25. Tom-D

    Tom-D Taxi to Parking

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    I do, If you really don't believe me call your
    FSDO and ask if disassembly of a primer pump is PM
     
  26. weirdjim

    weirdjim Ejection Handle Pulled

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    And I am both, and you are wrong.

    But there is nothing new about that, is there?

    Jim
     
  27. sixpacker

    sixpacker Pre-takeoff checklist

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    We ARE talking about keeping shafts well lubed after all.
     
  28. Tom-D

    Tom-D Taxi to Parking

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    All Ron's groupies must now rally around and make jokes of me telling him is is wrong.
     
  29. denverpilot

    denverpilot Tied Down PoA Supporter

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    So you're saying we're going from keeping plungers well lubed, to a circle jerk, then?
     
  30. Pedals2Paddles

    Pedals2Paddles Cleared for Takeoff

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    I should have asked something less controversial...


    << Sent from my mobile device at 0agl >>
     
  31. tmyers

    tmyers En-Route

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    I am definately not on of Ron's groupies.
     
  32. poadeleted20

    poadeleted20 Deleted

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    Not teaching maintenance (that's why I always suggest getting a mechanic to teach you how to do oil changes, primer lube, etc), just what the applicable regulations are for pilots. You being a licensed mechanic, the regulatory question of "maintenance" versus "preventive maintenance" is irrelevant to you as you can legally do both yourself, so I would not expect it to matter to you nor would I expect you to be familiar with how to teach it to pilots.

    And yes, I'm going to call the Seattle FSDO on Monday and ask your PMI what s/he told you.
     
  33. Tom-D

    Tom-D Taxi to Parking

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    Remember my PMA just retired, so I doubt the person on the phone will actually know me.

    You'll find that FSDO has not advised me on this because it is to obvious.

    You still have not shown where a pilot can disassemble any fuel system part. no matter what you call it.

    The only items an owner can remove from the aircraft are what is quoted in 43-A (c ) and a primer pump plunger isn't one..

    Got the balls to call your friend "Tony" and tell him you have taken the plunger out of the Grumman's pump and ask him who should return it to service.
     
    Last edited: Jan 3, 2015
  34. N801BH

    N801BH Touchdown! Greaser! Gone West

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    :popcorn::popcorn::popcorn:
     
  35. Tom-D

    Tom-D Taxi to Parking

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    want their number? 1-425-227-2883 who answers that number will be my old PMI's relief
     
  36. Tom-D

    Tom-D Taxi to Parking

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    Didn't you just advise a owner to pull the plunge and lubricate it? That is teaching. and wrong.
     
  37. Tom-D

    Tom-D Taxi to Parking

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    Pedals you did just fine Just because you got bad advice doesn't make YOU wrong.
     
  38. weirdjim

    weirdjim Ejection Handle Pulled

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    And quite frankly, you ask the LEGALITY of it, Pedals. Now if you want real advice, here you go.

    First of all, as I recall, the O-rings in the 172 fuel primer are NOT your regular off-the-shelf AN O-rings. I believe that they are oval-rings and not O-rings. Tom, who has probably done a thousand of them to my one, may correct me. But as I recall, the manufacturer got some off the wall ()-ring and put it onto the primer shaft.

    Second of all, "removal of (nonimportant) parts and repair of (noncomplex) systems is a gray area. Any FAA gooney that busts you for taking a primer apart (knurled knob on the panel and pulling out the shaft AFTER shutting off the gas) and calling that complex has a problem of craniorectal insertion. But they hold the hammer, so be careful.

    Third, the amount of lube you use on the rings is about the amount that would fill a flea's navel (or an FAA inspector's heart, your call). More than that and you are going to cob up the output check-valve to the point where you have to pull the whole thing and clean it ... and in my book, THAT is the dividing line between owner maintenance and A (not A&P) repair.

    Fourth, if you are alone in the hangar when this happens, who is going to rat on you?

    Fifth, if somebody lubed this thing a few months ago and it has now gotten stiff, YOU have been stiffed. THat lube ought to last five or ten years.

    Tom, please chime in for stuff I may have forgotten.

    Ron, if you want my PMI's name, you can go to the Sacramento FSDO and ask for Helen Hunt. THat is, you can go to Helen Hunt for it.

    Thanks,

    Jim
     
    Last edited: Jan 3, 2015
  39. poadeleted20

    poadeleted20 Deleted

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    Shouldn't matter.

    :sigh: Let us know when you do talk to the FAA.
     
  40. poadeleted20

    poadeleted20 Deleted

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    Nicely covered in the regulations quoted above -- lubrication with noncomplex assembly is preventive maintenance. Lubrication of the primer plunger does not require any complex work, so it's PM. Replacing the O-rings is another story, since that is not in the PM list, and will require your A&P's supervision and signature.

    And you can get them from Aircraft Spruce if you mechanic doesn't have any around, but that's not the issue.

    I've talked to FSDO Airworthiness people about more complicated operations, and they agreed those were PM, so I'm not worried about this part, but if you're not sure, do indeed call your FSDO to make sure.

    If you mess it up and additional repair is required, then you should get a mechanic involved. But if you do what I first suggested and get your mechanic to teach you how to do it correctly the first time, it should not come to that.