High Oil Pressure

I have a IO-320 that exhibits high oil pressure warning after take-off (90psi+) on a GRT EFIS. I reduce power to keep below the red 90psi warning. If at safe altitude, I will pull the throttle back to the stop, pitch up to slow rpm (fixed pitch) and observe the oil pressure is around 63 psi. When I land and shut down, and restart, the oil pressure now becomes normal on ground and also in flight regime. This has happened several times. I'm thinking sticky oil pressure relief valve or perhaps bad veritherm. Anybody have any similar experience with this kind of scenario?

What's the temp doing at that time?

I've got an IO-320-B1A that will sit bang on 90psi until temp increases, which is a challenge due the plenum, but once engine warms it sits @ 80psi all day.

Do you have the older style oil pressure sensor that relies on a case ground? We had the same issue and replaced it with the new style sensor. Just a thought.

I think max is 95 psi on that engine for takeoff, so when you say 90+ are you below 95? But the first question is whether this is a change in what you are used to seeing? If so, I would check the sender first. As someone asked, what are the temps? If it's a new engine, it is most likely normal and will come down in a bit.

Vic

I'm with Kevin Phelps on this one. I just went through the same issue. Looked at my EFIS manufacturer's website to order new sender thinking that was the problem. They had a writeup about bad ground on single pole sender and suggested brazing a ground wire to the sender case and grounding directly to the engine. I soldered a ground wire to the sender case and my oil pressure is now solid and normal in its range.

Based upon your description, I would be thinking of a problem in the sensor. If the pressure stays high throughout the flight, but after shut down and restart, the same flying conditions produce a lower pressure, something is likely hanging up in the sensor. It is really just a diaphragm and a spring.

The Vernatherm can't really increase pressure at the sensor as it is downstream. Hanging up in pressure relief mechanism is possible, given your symptoms, but much less likely than the sensor hanging up.

Oil viscosity needs to be considered. Cold oil is thicker and can increase the oil pressure if the relief cannot shed enough oil volume to meet the target pressure. However, that condition should be gone once oil temps are around 100* and this is not consistent with your symptoms. I would be looking for something "hanging up" if understand your symptoms correctly.

It would not be abnormal for your pressure to be 95 (high RPMs) when cold and then slowly reduce to 85 (high RPM) when warm. It is abnormal for your pressure to be 95 on the entire flight after a cold start, but 85 on the next flight with a warm start. When troubleshooting, always compare pressures at a common RPM. It is normal for engines to produce different pressures at different RPMs.

Good luck,

Larry