Oil pressure blanks - - - after start

[P_Reid]

I have a D120 with Kavlico sensor for oil pressure. Occasionally I notice on start the oil pressure spikes rapidly as the starter is engaged. A couple of times the oil pressure then shows 3 - lines (- - -) and an over pressure message. If I recycle then D120 the oil pressure behaves normally.
It seems that the voltage drop on startup causes the problem. Is there a solution for this other than recycling the D120?

Thanks Peter

 

[GKC Aviation]

Could be air in the oil pressure line to the sensor. This might cause the rising oil pressure to compress the air in the line and spike the sensor.
Sort of like water hammer in your water lines at home when you turn a tap on and off with air in the pipes.

 

[jherzog01]

I have a D120 with Kavlico sensor for oil pressure. Occasionally I notice on start the oil pressure spikes rapidly as the starter is engaged. A couple of times the oil pressure then shows 3 - lines (- - -) and an over pressure message. If I recycle then D120 the oil pressure behaves normally.
It seems that the voltage drop on startup causes the problem. Is there a solution for this other than recycling the D120?

Thanks Peter

Suggest checking the sensor for a slight leak. Dynon put out a service bulletin in 2020 about potential leaks in Kavlico pressure sensors:
https://www.dynonavionics.com/bulletins/support_bulletin_050620E.php

 

[airguy]

Is the sensor located on the engine or on the firewall? If on the engine itself, you can be seeing the result of a poor engine ground to the airframe - and the heavy starter current is looking for a path to ground through the pressure sensor line.

 

[P_Reid]

Thanks for the replies. The sensor is mounted on the firewall in the standard position for the RV-10.
I‘ll check it for air, but still wonder if it has something to do with the voltage drop when the engine is cranking???
Although thinking about it more - if I see it happening again I’ll take note of the fuel pressure sensor, as it is also the same type of sensor and also feed with 5V