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  #1  
Old 11-10-2018, 11:40 AM
PilotBrent PilotBrent is offline
 
Join Date: Dec 2011
Location: Hackettstown, NJ
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Default Oil Pressure Sensor - Trouble shooting question

Looking for some advise regarding the setup of a new oil pressure sensor.

Background: During test flight last weekend after a fuel tank leak repair, I suddenly had a drop in oil pressure just after liftoff. (dropped into the yellow range which it never does) Headed around to land and the pressure fluctuated a lot, and hit zero a few times. No temp increases, engine ran normally. After landing oil pressure recovered to normal. Could not find a problem on the ground/or during another runup. On next takeoff roll, it began to drop again, so I aborted and assumed it was just a bad sensor.

Just installed a KAVLICO 0-150psi sensor purchased from Dynon. P/N 101693-000. Updated Skyview EMS sensor page (screen shot below) at C37/P6 with what I think is the correct item on the menu. But I'm now getting a 14psi pressure reading on the ground without the engine running. Scratching my head as to why it isn't at/near zero. Have not started the engine yet.

I understand there are some errors in these pressure sensors (+/- 5%?) but 14psi doesn't seem normal. Is it possible they put a lower range sensor in the parts bag? (I forgot to look at the small print on the sensor itself). Is there another setting in Skyview that I missed updating...or did I mess up the sensor page in error? Does the wiring for the sensor for Skyview (standard Van's setup) need to be changed when switching to Kavlico sensors? Any ideas welcome.
thanks, Brent.

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Last edited by PilotBrent : 11-10-2018 at 06:58 PM.
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  #2  
Old 11-10-2018, 12:04 PM
lr172 lr172 is offline
 
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Default

Most of these have a dead zone at the baseline. I thought the specs said they start reading at 5 or 10 PSI for a 150 PSI unit, but can't recall exactly. You can find the specs online. 15 seems high, but acceptable, assuming the sensor reads correctly above that. You're clearly in the red once below 25 PSI, even at idle.

Given the error, it may be prudent to confirm your sensors accuracy. You can connect it via a vynal hose to your compressed air source for testing.
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  #3  
Old 11-10-2018, 12:34 PM
BillL BillL is offline
 
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Location: Central IL
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Default Just for perspective.

It looks like the correct sensor connection. Statistically, sensors are less reliable than the oil system. Having said that, if it does not act perfectly normal once starting, I would install a mechanical gage with a hose to be seen from the cockpit and use that to confirm there is no issue with the lube pressure. That would eliminate possibility of an expensive lesson while troubleshooting a wiring issue.

FYI http://cdn1.kavlico.com/downloads/da...Sheet_(US).pdf

0.5-4.5VDC output - 3 wire= ground, 5VDC, output

Edit #2 - Consult Dynon support information. For some Dynon devices this sensor WILL READ 14 PSI and is normal.
Here is a reference, but do not know if it applies to your SKYVIEW. https://www.dynonavionics.com/includ...sors-Rev_C.pdf
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Last edited by BillL : 11-11-2018 at 06:29 AM.
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  #4  
Old 11-10-2018, 02:55 PM
gasman gasman is offline
 
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If it's a single wire sender, you may have a grounding issue between the motor and the airframe. To test this, run a jumper wire from the base if the sender to the same ground that the gauge is using and see if it goes to "0" from 14 on the ground.
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  #5  
Old 11-10-2018, 04:23 PM
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RV7A Flyer RV7A Flyer is offline
 
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Quote:
Originally Posted by gasman View Post
If it's a single wire sender, you may have a grounding issue between the motor and the airframe. To test this, run a jumper wire from the base if the sender to the same ground that the gauge is using and see if it goes to "0" from 14 on the ground.
OP said he has Kavlico transducer, which is 3 wire, not 1.
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Old 11-10-2018, 05:58 PM
Mich48041 Mich48041 is offline
 
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I do not see a 200 ohm resistor on Van's Skyview schematic.
Brent, does your oil pressure sender have 3 wires?
If so, is one of them securely grounded?
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  #7  
Old 11-11-2018, 06:59 AM
skydiverlv skydiverlv is offline
 
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Do you have the V+ wire connected to 5V supply or 12V? The Kavlico requires 5V+. The old sensor was 12V+
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  #8  
Old 11-11-2018, 09:16 AM
Mich48041 Mich48041 is offline
 
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Van's Skyview schematic shows 12 volts connected to the oil pressure sender.
However, Dynon's website seems to indicate 5 volts.
I would try 5 volts to see if the sensor works better.
5 volts are available at the manifold pressure sensor.
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  #9  
Old 11-11-2018, 11:43 AM
PilotBrent PilotBrent is offline
 
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Followup - I could not get a normal (engine off) reading after testing the various two wire combinations and adding a third wire from the sensor for a new ground. (Van's original setup only has 2 wires to the sensor)

Finally got around to checking the voltage on each of the 2 wires. One read 4.9v and the other 11.7v. No wonder the readings on the panel didn't make sense. I swapped out the voltage regulator to a spare one I had on hand, and rechecked the measurements. One read 4.9v and the other 0.4. It appears that a failing regulator had a disproportionate impact on this pressure sensor. I had not noticed anything else odd on the panel.

I then eventually identified which two wires to the sensor and a third to a ground that gave me a reading of only 4psi on the panel. (the wire colors red, green, black from the Dynon supplied plug, didn't seem to correspond correctly) Ran the engine and this seemed to work, with the oil pressure measurements mostly in the 50s & 60s. But, it soon began to jump around a lot and the engine didn't run as smoothly at is should. Jumped out and found spilled fuel around the left carb. Yes, after all this I had a bad float. (the were just replaced in the spring!)

I will fly again some day....
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