Oil pressure spikes
 

Folks,

I have an IO-360 in my 8 and had an oil pressure event a few weeks ago and haven't seen it since, although I'v only done a few short local flights since.

I was on my way back to 57C (East Troy WI) from KMGM (Montgomery AL), flying along at 6500' about 2 hours into the flight when my AFS 4500 sounded an oil pressure alert. Looking down it was indicating the pressure was 117 PSI, where normally it's around 86.

I was probably 40 or 50 miles from the nearest airport so the pucker factor went way up.

So I decided to keep going while constantly looking for emergency landing sites (slim pickins there) and stayed pretty keenly focused on the motor parameters. My oil temp stayed put in the green and none of the other temps were abnormal.

As I went, the pressure very slowly came down to about 95 psi which made me feel quite a bit better and so I flew past the first landing spot. By now I was getting pretty close to Louisville (I was pushed well east avoiding a convective system moving across the area) and airports were more plentiful so I kept going.

The oil pressure climbed again to around 112 and slowly went down again and kept fluctuating between around 99 and 110 psi. Again, everything else stayed normal. I sort of thought I might have a sending unit problem, but the pressure kept fluctuating and didn't just go to some out of range point so I'm not too sure one way or the other.

I kept going, navigating the front edge of the weather which started getting me closer to my acceptable minimums and together with the oil pressure problem I was thinking I'd better get her on the ground as I was up to two strikes!

I squeezed between the nasty weather and the Cleveland Class Bravo and set my sights on KMIE (Muncie IN) for a stop, fuel, investigate the oil problem and lunch. (there is a very nice restaurant right next to the FBO).

Safely on the ground I checked over everything I could see and found nothing out of the ordinary. Oil level fine, no oil on anything under the cowl, not a clue about anything.

With a full belly, full fuel and about a 1 hour leg left I launched, figuring I'd again keep a very close eye on things.

Well the oil pressure went to 86 PSI and stayed right there until I got home. I've done a couple of short local flights since and again, everything stays normal.

Anyone able to postulate on this?

Thanks for any help.

I have had a couple VDO pressure sensors go bad, giving erratic and high indications on my Dynon. Last replacement got an upgrade to a Kavlico sensor, no problems since.
What display and sensor do you have?

AFS 4500 and whatever sensor they sent with it. No idea of brand.

I agree that the prime suspect is the sensor. It is just a spring and diaphragm. When they wear, they routinely read high. If it is a VDO sensor and it likely is, I would replace it and watch closely.

Larry

pp. 7-50 and 7-51 here
http://dynonavionics.com/public_html...LL_SKYVIEW.pdf

show the new Kavlico sensors and the old VDO sensors. The VDOs suck, IMHO, and demonstrate exactly the failure mode you describe: intermittent, noisy and high.

I'll bet dollars to donuts if you open the cowling, you'll find the fuel pressure and oil pressure senders are VDOs. Do yourself a favor and upgrade to Kavlicos for both of them.

Yep, I have the old style VDO sensors. Guess I'll be changing them. Thanks!

I have had a simular thing with my RPM warning. Found that I had a loose pin on the plug in the back of the AFS4500.

If I may, what would cause an actual rise in oil pressure during normal operation of an otherwise healthy engine?

Wrote about it in another post recently. I had the same or similar happen. If its the single pole sensor, they ground through the manifold it is screwed into which is grounded to the firewall and untimately shares a ground with your EFIS. This ground is unreliable. My EFIS manufacturer recommended brazing a ground wire to the sender case and grounding directly to the engine case. I followed this recommendation and it now works as it should.
Previously, I also had intermittent high oil pressure readings like yours. When it went to 130 psi, I started looking for a fix. That is when I read the article on my EFIS manufacturer's web page which seems to have solved my problem

Oil pressure is the one instrument which needs a mechanical backup. What would you have done if the error (assuming it is an indication error) had shown 20psi?