Question: Diagnosing a low oil pressure warning

Hi all,

Today I had a low oil pressure warning go off about 10 minutes into my flight while doing light airwork. I performed the annual at the end of September and the oil filter and screen were clean at that time. I have been out of town a lot on business, so have been unable to fly for about 6 weeks... so this was a -rust remover- flight for me. (hopefully not engine rust! )

I returned immediately to the airport while getting a code to stay high through Ottawa's Class C to get back to Carp for a straight in to our active. All was OK.

This has happened to me once before after an oil change and a long period of inactivity on the plane (2 years ago) The last time this happened, I drained the new oil and inspected the filter and screen for debris and found none. I removed the Vernatherm and inspected it, and could not find anything suspicious there either. I buttoned it back up, test flew it, and all was OK, and has been fine until now.

Other than repeating the steps I did in 2012, should I be looking elsewhere for the cause?

The oil pressure reading would drop to 20-23 PSI at 2400 RPM, then return to normal for a while, then drop again. It ran at 85-90 PSI at 1800 RPM once I was back in front of my hanger. I haven't pulled the engine log yet, but will look at that later this week.

Any suggestions would be welcome.

Thanks,

Chris

I had a similar problem during my phase 1 testing that turned out to be a poor ground on the oil pressure transmitter...might be something worth looking at.

I'd suspect the pressure transducer.

What kind do you have?

It might work to add another gauge in parallel to see if they both drop, or just one. If they both go down, maybe a more serious problem. Pump?
Dave

I am working through the same problem on my 6A with an O-360-A1A. I currently believe the pressure is fine and that the gauge/transducer/wiring is the issue. A real oil pressure problem would not come and go, but an electrical problem can do that.

My .02 worth---I'm not an engine guy, or a avionics guy, but I would verify with a known good mechanical guage before tearing things apart. Alot of guys have spent alot of time chasing things that simply weren't there.
Sounds like a transducer/wire/connection issue to me---but connect a hose/guage to the oil pressure port FIRST to make sure.
Tom

Most likely electrical

An update...

I pulled the recording file off of the Odyssey at lunchtime, and when I plot Oil Pressure and oil temperature, both plots have erratic readings for about 6 minutes until I throttled back at the end of my approach. (both plots show changes which are moving way too fast for something physical)
I added Fuel pressure, and it too has erratic readings during the same time period.
CHTs and EGTs were steady during the same time, so I will have to isolate the bad ground.... The oilT, oilP and fuelP are grounded on the forest of tabs on my firewall. Probably a good place to start looking.

Thanks all for the suggestions.

Chris

other possible reasons

Two other possible reasons I have experienced lately

1) Air bubble in the oil pressure line from engine to sensor. Esp if that line or the sensor have been removed lately or if its a new engine. In this case, remove the lower plugs, ground any mags, crack the fitting at the sensor end, and crank for 15 secs at a time until you get oil pushing out the fitting, then tighten back up.

2) Piece of debris on the ball/seat of the oil pressure regulator. Remove the regulator, clean the ball and seat, reinstall with new crush gasket.

Looks like ground problem

I had similar situation with couple of gages at same time installed switch with ground wire and when problem apeared turn it on all sabilized immediately then found bad crymp