Oil pressure spikes and variances.

[lpaaruule]

On a recent flight I started having high oil spikes. The pressure would max out the scale at 80PSI.

I suspected the oil pressure sender, so I replaced it with a new one. Went for another short flight, and the spikes were even worse.

This morning I replaced much of the wire that goes to the pressure sender. I suspected that maybe there was a bad crimp on the ring terminal, or where I but spliced an extension to the wire that was supplied with the engine monitor.

Thinking that I had resolved the issue, I taxi'd around, and then did a run-up. Unfortunately the oil pressure still spiked to 80 PSI. Sometimes it would even stay there until I changed RPM. It even spiked to 80 psi at idle. I found that every time I reduced the power to idle, there would be a sudden pressure spike. At around 1400RPM the pressure would return to 40 psi.

I suppose it could still be a wiring issue, but a shorted wire to ground would indicate 0 psi, and I replaced the part of the wire that I suspected could be broken. I was unable to get the oil pressure to spike without the engine running. This involved banging, shaking, and heating different sections of the wire.

So, with the possibility that it's an engine issue, I'm not going to risk flying again until the issue is resolved....:-(

[GraemeSmith]

Don't know the Jabiru but on the AeroVee that can be the pressure relief bypass valve sticking and not opening. Could be:

Debris in the valve
or
Oil is cold and not warming up enough and the valve is "sticky" in the thick oil.

Is it suddenly colder than you are used to? In my case - after checking for operation and correct clearance of the sprung plunger (in the AeroVee - don't know how the Jab does it) a baffle over the oil cooler, allowing the oil to get up to temperature resolved this.

[lpaaruule]

According to the engine overhaul manual, checking the relief valve appears to be a simple task. I think I'll run out to the hanger this morning and check it out.

The spikes only seem to happen after the oil is warmed up. Also, my oil pan is kept at approx 60F with a heater 24/7.

Thanks

[MichaelFarley56]

The pressure relief valve is a pretty basic setup but if the plunger is sticking at all that could cause your issue.

Have you added oil to the engine lately? I’ve read reports that adding too much oil to the engine can also cause similar situations. These engines seem happiest when they are kept maybe a half quart under full.

[lpaaruule]

I just removed the oil filter, and no oil poured out. I filled it when I did an oil change a couple weeks ago.

Oil level is midrange between low and height marks.

It’s getting scary...glad I heeded the oil pressure warning and didn’t fly yesterday.

[lpaaruule]

The relief valve looked fine other than a tiny bit of rust. Very little scuffing in the relief orifice. I used safety wire to very lightly feel for scratches, nothing. I lightly polished the valve with gray scotchbrite pad. Cleaned and lubed it, then put it back together.

Ran the engine for a few minutes. Oil pressure normal. Loosened oil filter, and oil poured out. I guess they don't hole much oil if they've been sitting. I’ve only ever removed the filter after warming the engine.

[NWade]

Paul - Not sure about the Jab, but I know from experience (search my posts for my oil cooler blowout & write-up) that there is a fine line between the AeroVee oil control piston moving freely and getting stuck. One thing to think about is that as the engine and oil warms up, the hot metal will expand. It could be that you had such a tight tolerance that the temperature change (or perhaps a small bit of corrosion) was enough to prevent proper movement.

Good luck, I hope the issue has been fully resolved with your latest action!

--Noel
Sonex #1339
AeroVee Turbo
[learning how to paint her now, first flight soon]

[lpaaruule]

To try to eliminate the possibility that the issue is with the engine monitor, I disconnected the wire from the pressure sensor, and attached a 100 ohm resistor to it, and connected the other end of the resistor to ground. This forced the engine monitor to display a constant 37 psi. I put the plane back together, and taxied around until the engine got to operating temp. The oil pressure remained at 37 psi, so it's really looking like it's an engine issue, as it's unlikely that my new oil pressure sensor would immediately fail the same way the old one "failed".

I removed the resistor from the wire and reconnected it to the oil pressure sensor. As soon as I started to taxi, the pressure shot up to 80 psi. if I changed the RPM it would return to around 40 psi. I played with various RPMs for about a minute, and decided that I I was pushing my luck running the engine as this point.

So, it looks like I'll be contacting Jabiru tomorrow, if they're open.

[sonex892.]

Hi Paul. You say the gauge goes to max scale 80 psi. There is a fair chance this is just a grounding issue.
Steve

[lpaaruule]

Hi Steve,

If I had a grounding issue, I think that would have shown up when I simulated the sensor with a 100 ohm resistor. The resistor was grounded to the engine. Also, with the real sensor, I always get zero psi when the engine is off. No amount of shaking, banging, or heating has revealed a wiring issue.

I’m still considering all ideas though.

It only seems to happen once the engine is hot. This leads my to think the relief valve is sticking.