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  #11  
Old 03-24-2020, 01:07 PM
Charliesixtysix Charliesixtysix is offline
 
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The one we are sorting did ( but reading high in our case) and turned out, as thought above, to be grounding fault.

The main thing pointing to indication error is just how closely pressure change corresponds to rpm variation and how little lag there is in changes - oil pressure does not tend to change as fast as those indications in the OP?s log.

My money is poor ground or a shielding fault.
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  #12  
Old 03-24-2020, 02:02 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Charliesixtysix View Post
The one we are sorting did ( but reading high in our case) and turned out, as thought above, to be grounding fault.

The main thing pointing to indication error is just how closely pressure change corresponds to rpm variation and how little lag there is in changes - oil pressure does not tend to change as fast as those indications in the OP’s log.

My money is poor ground or a shielding fault.
without regulation, oil flow and therefore indirectly pressure, is directly related to RPM, as the oil pump is driven 1:1 off the crankshaft. pump output volume is directly proportional to crank RPM. It is the relief circuit that stabilizes the pressure by diverting volume.

Larry
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Last edited by lr172 : 03-24-2020 at 02:04 PM.
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  #13  
Old 03-24-2020, 02:03 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Charliesixtysix View Post
The one we are sorting did ( but reading high in our case) and turned out, as thought above, to be grounding fault.

The main thing pointing to indication error is just how closely pressure change corresponds to rpm variation and how little lag there is in changes - oil pressure does not tend to change as fast as those indications in the OP’s log.

My money is poor ground or a shielding fault.
without regulation, oil flow and therefore indirectly pressure, is directly related to RPM, as the oil pump is driven 1:1 off the crankshaft. pump output is directly proportional to crank RPM. It is the relief circuit that stabilizes the pressure by diverting volume to maintain a set pressure. When the ball is stuck off it's seat, pressure will directly follow RPM until the opening is no longer great enough for the spring to hold the ball there. Then it will flat line, as the ball / spring is able to do it's job.

I would be very surprised to find the symptoms shown on the chart to be the result of an indicator problem. Simply too close of a correlation between pressure and RPM to be an indicator problem.

I have been wrong often, so not suggesting to skip the step of checking instrumentation. Just doesn't seem likely. The sudden nature of it also makes instuments less likely. The chart shows an almost instant change from normal to abnormal behavior.

Larry
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Last edited by lr172 : 03-24-2020 at 02:16 PM.
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  #14  
Old 03-24-2020, 03:37 PM
Charliesixtysix Charliesixtysix is offline
 
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Yes, various possible causes.
Hopefully the OP will update with findings in due course.
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  #15  
Old 03-24-2020, 04:22 PM
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AlexPeterson AlexPeterson is offline
 
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First, thanks to all those who replied. Charlie - you still want to put some money on it being an indication?...hahah.

Readings confirmed with the mechanical gauge, and today was a repeat of yesterday. I will pull the relief valve and have a look at it. The observations fit a leaking valve, but it is also hard to imagine it being so stable. I.e., one would think whatever was under the seat would have gone downstream.

I'll report what I learn.

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  #16  
Old 03-24-2020, 09:46 PM
lr172 lr172 is offline
 
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Do you have a constant speed prop? Looking past the relief to a possible leakage point. Something in the prop/crank cavity area would be my first guess at a sudden occurrence leakage point. Not too many areas that would produce a sudden and significant bleed off of oil volume. Assuming your relief checks out ok.

Larry
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Last edited by lr172 : 03-25-2020 at 07:22 AM.
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  #17  
Old 03-24-2020, 09:57 PM
Taltruda Taltruda is offline
 
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Default My money

My money is on the relief valve.. let us know!
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  #18  
Old 03-25-2020, 01:18 AM
Charliesixtysix Charliesixtysix is offline
 
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Ah well, some you win.... it was wiring in our case (and I did say right t the start, subject to verifiction by mechnical gauge first ....). ;-)

Hope it proves to be simple and not too expensive to fix.
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  #19  
Old 03-25-2020, 09:23 AM
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AlexPeterson AlexPeterson is offline
 
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Default Culprit Found!

The little lumpy ball at about the 5:00 position was the cause. Oil pressure normal again. The ball is most likely lead, as it feels metallic when I scratched on it with the corner of a razor blade. It measures .020" in diameter. Amazing that it simply parked there, and I'm quite happy it did so that I could find the smoking gun. Thanks for the thoughts.

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  #20  
Old 03-25-2020, 09:33 AM
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rv8ch rv8ch is offline
 
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Default excellent outcome

Thanks for sharing this story - one to file away, a lot to learn here.
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