Eratic Oil Pressure

[kiwibob]

Not the sort of thing you want to see on a pleasant evening flight over the harbour. The red bright high pressure oil light caught my attentionopt1.jpg.

During the next several minutes of tension the pressure was all over the place. I landed at the fortunately nearby airport and was able to have the engine tested the next day with a direct reading gauge. All normal. Several circuits and also normal.

A few days later I made a two hour flight (over land) also all normal. Satisfied that the problem had at least gone away I returned over the harbour and the pressure dropped to zero for several very long moments before it started moving all over the place again.

I'm pretty convinced this is a reading issue as I naturally messed up the crosswind landing and had to go around and the engine ran fine.

Another investigation found that the earth bolt was not as firm as might be desired. A further test fly a few days later (very close to the field) was again all normal.

I've bought another transducer but not yet fitted it. I'd be interested in anyone's thoughts on what next (the plane is 20-30 minutes to the nearest field with any facilities).

[stede52]

I've had that same situation happen to me in my plane (not the CC) a couple times, I had a high oil pressure reading on one flight and erratic or fine on the next flight. In both cases the transducer was going bad. I verified the pressure was fine by testing it with an oil line to an analog gauge. I was concerned about the issue but I would have been much more concerned if the pressure dropped dramatically.

[cityrancher]

I had the same problem with a Legend Cub. It was a faulty transducer.

[kiwibob]

I had the same problem with a Legend Cub. It was a faulty transducer.

Thanks Stede52 and Cityrancher. I shall get the new one fitted as soon as the holiday season here is over.

[Pete D]

It definitely sounds like the transducer is going bad, or possibly an issue with the wire crimps for the connectors at the transducer. I have seen this on various makes/models of a/c with that EI gauge.

[kiwibob]

It definitely sounds like the transducer is going bad, or possibly an issue with the wire crimps for the connectors at the transducer. I have seen this on various makes/models of a/c with that EI gauge.

Thanks Pete, I will definitely check those when I replace the transducer. Tightening the earth point in the meantime has resulted in an "all in the green" situation.

[kiwibob]

It definitely sounds like the transducer is going bad, or possibly an issue with the wire crimps for the connectors at the transducer. I have seen this on various makes/models of a/c with that EI gauge.

I have the new transducer but have not yet fitted it. I now have 20 hours since tightening the earth point and the pressure has remained firmly in the green. Hopefully I now have a spare transducer.

[kiwibob]

I have the new transducer but have not yet fitted it. I now have 20 hours since tightening the earth point and the pressure has remained firmly in the green. Hopefully I now have a spare transducer.

Just to close this off. It's fifty hours since tightening the earth lug and the oil pressure is fine on the gauge. The oil analysis and filter showed nothing untoward so clearly it was a reading issue and the problem appears solved. (crosses fingers)

The nice people at Aircraft Spruce have taken back the new transducer I bought, less freight, restocking fee, yada, yada, yada.

[Joseph206]

It definitely sounds like the transducer is going bad, or possibly an issue with the wire crimps for the connectors at the transducer. I have seen this on various makes/models of a/c with that EI gauge.

I have been chasing erratic oil pressure for a couple months.
Just replaced Transducer sending unit. All Fixed. Found problem with analog gage.

[cityrancher]

I had an auto pilot in another aircraft that I spent a small fortune chasing an intermittent problem of "porpoising" altitude. S-Tec initially called for a rebuild of the servo, claiming carbon build up on the brushes causing the over correction. After replacing or overhauling several components the avionics tech went deeper into the problem. He had initially measured ground (earth) from the various components using the airframe. When he went through the entire system he found a "snap in" ground connector was not pushed in completely, probably installed improperly when initially installed by the factory. All would check good using the frame as ground. A simple connector not pushed in caused the intermittent problem. You may have solved the problem. I should have mentioned this earlier.