Zero oil pressure on an O-320

Discussion in 'Lycoming & Continental' started by freerangequark, Apr 19, 2018.

  1. Apr 19, 2018 #1

    freerangequark

    freerangequark

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    Went to fly today with a friend in their SuperCub.

    On startup, zero oil pressure. We checked the usual suspects and didn't find anything. Suspected a bad gauge but disconnected the OP line to see if oil was flowing. Nope. Blew out hoses and the oil cooler... nope. etc.

    How likely is an oil pump failure on a O-320-A1A? What are some possible failure modes and symptoms (aside from zero oil pressure)?

    Thanks,
    Glenn
     
  2. Apr 19, 2018 #2

    TFF1

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    All the bad oil pumps should have been replaced by now per ADs, shouldn't they? Check the suction screen, just in case.
     
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  3. Apr 19, 2018 #3

    freerangequark

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    You're talking about the oil sump screen?

    It was as clean as can be.
     
  4. Apr 19, 2018 #4

    Thorpdrvr

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    Usually there is a restrictor fitting on the accessory case that the oil pressure line connects to. It has a very small orifice that the oil must pass through to get to the gauge. I would remove the fitting and check for oil flow direct from the port in the accessory case. Could be a plugged fitting.
     
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  5. Apr 19, 2018 #5

    freerangequark

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    I'll check it out.
     
  6. Apr 19, 2018 #6

    RickRice

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    Has it been sitting for a long time? I don’t know if Lycomings are subject to this same problem, but the little Continentals can lose their prime and have the same thing happen. On J-3’s, the solution is to pick the tail up high for a few minutes and then try again. If that doesn’t work, on Continentals with oil filters, the next step is to remove the oil filter and pump the oil passages full using an oil can. (We’ve done it on non-filtered Continentals too, by removing the cover where the oil filter goes and pumping the passages full and replacing the cover. Just takes a little longer to get the cover back on versus spinning the filter back on.

    Again, I don’t know if any of this is applicable to Lycomings, as I’ve never had the problem on a Lyc, but thought I’d throw it out for consideration, as both actions are pretty easy to try.

    Good luck. Hope you get it sorted out soon and that it’s an easy fix.
     
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  7. Apr 19, 2018 #7

    ndlakesdreamer

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    What has been done since the last flight? I think the chance of a pump failure is less than zero unless there was a prop strike. Oil pump drives are huge in all the Lycomings.

    The pump drives off the back of the crank with the main crank gear. Most likely failure would be the crank gear bolt but if that failed none of the back case accessories would function. Lyc oil pumps are stout, I'm pretty sure they could grind up small varmits.
     
    Last edited: Apr 19, 2018
  8. Apr 19, 2018 #8

    freerangequark

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    The engine was ground run 2 weeks ago for an annual. Everything was fine.
     
  9. Apr 19, 2018 #9

    Morphewb

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    Check the pressure relief ball above the #3 cylinder. Normally crap under that ball will give you low oil pressure, not zero but it's worth checking.

    If for some out of the world reason the oil pump is still an old assembly which is driven by a Woodruff key on the OP drive shaft, the key shearing off would give you zero oil pressure with all the other gears in the accy case turning.

    Those models of the 0-320 have a vertical screen that surrounds a stainless pickup tube that's bolted to the accy case. I've never heard of one of those tubes failing or breaking off but you would get zip for oil pressure if it did.
     
    Last edited: Apr 19, 2018
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  10. Apr 19, 2018 #10

    Tomcat

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    I don't mean to sound demeaning or rude, but if the airplane was down for annual 2 weeks ago I presume the oil was drained at that time...was new oil put back in? Believe it or not I've seen this...
     
  11. Apr 19, 2018 #11

    Melndav

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    Has a friend who got his Staggerwing annualed by a local shop on the field. He told them to use the oil in the 55gal. drum when they changed it. After the annual the had low/no oil pressure that quickly got worse as the engine warmed up. They troubleshot it for a good week until we asked what kind of oil they put back in and we're told it came from the 55 gal. drum in the hanger. When we got him to show us it was the drum clearly marked "Corvus oil."
     
  12. Apr 19, 2018 #12

    Chris McMillin

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    I'm gonna hurl!
    Chris...
     
  13. Apr 19, 2018 #13

    freerangequark

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    We checked the seat of the ball and that was all clean.

    The logbook for the engine says that the oil pump housing is 76060 and the impeller is 60746 (Double-D, Steel). 60746 does not have a keyway or woodruff key from what I can tell. There is a lot of confusing information out there regarding the ADs on this. Can anyone confirm that 60746 is the correct impeller gear number?

    The restricted nipple for the oil pressure line is clear.

    Here are some pictures of what is on the back of the accessory case.

    IMG_20180419_111539.jpg

    IMG_20180419_111148.jpg

    IMG_20180419_111522.jpg
     
    Last edited: Apr 19, 2018
  14. Apr 19, 2018 #14

    freerangequark

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    Plenty of oil :)
     
  15. Apr 19, 2018 #15

    freerangequark

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    Turns out there was a lapse of several days from the time the oil was drained to the time new oil was put in. Its possible that the oil pump lost its prime.
     
  16. Apr 19, 2018 #16

    TFF1

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    I would pull the oil filter if you have not. You can hand pull it through and see if some pumps. You can also prime the filter and shoot some back in the engine. If the crank is turning its turning the pump direct. You could always pull a mag and watch the gears with a mirror or borescope. Nothing like a different oil cooler installed at the annual or any other type of heavy maintenance done ?
     
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  17. Apr 19, 2018 #17

    freerangequark

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    Not a thing major during the annual. It's really odd.

    How fast does the engine need to turn to effectively pump oil? If I took the plugs out and ran the starter, should that do it?

    Thanks!
     
  18. Apr 19, 2018 #18

    Morphewb

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    A healthy starter/battery combo will spin the engine more than fast enough. Are you able to take the oil pressure hose off at the fitting on the engine? That's a convenient place to use but the engine mount might be in the way.


    I usually hook a battery charger to the battery if I'm cycling a landing gear or pre oiling an engine. Just make sure you don't get the starter too hot.
     
    Last edited: Apr 19, 2018
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  19. Apr 19, 2018 #19

    Larry Lyons

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    Your right Ben spinning my 0-235 after sitting for almost 20years I pulled the plugs and the starter produced 30 psi in no time at all.
     
  20. Apr 19, 2018 #20

    freerangequark

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    Any idea where I can find a parts manual online for the a narrowdeck O-320?

    Gotta get replacement gaskets for the things we're checking.

    Thanks,
    Glenn
     

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