Oil pressure spikes and variances.

[tx_swordguy]

I saw that you cleaned the oil psi relief piston but did you wipe the tube it rides in clean? A small amount of grit lodged between the wall and the piston can make it stick. I know this from a revmaster but similar concept on jab. Just dont see another way for the oil psi to go that high unless the relief valve is acting up. That is if the reading is accurate. If it was low it would be a different story

[lpaaruule]

I used a q-tip to clear out oil so I could see the inside of the tube. I didn’t see any grit. I have a feeling I’ll be opening it back up again soon though, so I’ll double check.

[wlarson861]

I have used an electronic oil pressure sender(VDO) on two engines tied to my MGL Enigma. They never worked right! With the Jabiru I still get weird readings on the eifis as far as oil pressure. After I blew my oil cooler I added a mechanical oil pressure gauge. The VDO even on the Jabiru is erratic but the mechanical indicates 40 to 50 psi in flight. The Vdo is not accurate and engine decisions should never be based on what they report. Get a good mechanical oil pressure gauge and use that

[lpaaruule]

I contacted Jabiru, and the guy there said that he's never seen the engine make over 60 psi, even cold, and if it's an engine issue, the relief valve is the only thing he can think of.

So, I'm going to try setting the oil pressure limit to the max that the engine monitor will allow. If it pegs the limit, then I'll know it's not the engine (assuming the scaling doesn't change). I should be able to test that by simply disconnecting the wire from the pressure sender.

[DCASonex]

Possible oil pressure relief valve problem, but 80 PSI is what you will see with an open circuit so much more likely that it is a wiring / grounding problem.

David A.

[lpaaruule]

My plan on setting the limit high didn't help. The display would only read 80 psi even with the pressure sender wire unplugged.

I added a separate ground to the sender, but unfortunately couldn't get the engine started (I think I flooded it), before the battery was too low. I hope to get out to the airport today, and try it out with a fully charged battery.

[lpaaruule]

Finally got back to the hanger today. Ran the engine with the separate ground added to the oil pressure sender housing.

Looked good at first, but as soon as the engine warmed up, the oil pressure started spiking to 80 psi again. Coincidently, the fuel flow was obviously incorrect, however I might have messed up the settings when I was looking through them. Also, the oil temp was unusually low, though it did rise, and seemed ok.

I'm starting to wonder if something is wrong with the engine monitor. I think I'll send GRT an email.

[onex28]

I second wlarsom861’s suggestion. Hook up a mechanical pressure gauge for a second pressure opinion.

David W

[sonex892.]

I'm starting to wonder if something is wrong with the engine monitor. I think I'll send GRT an email.

If the wiring is good, the internal monitor circuitry could be what is breaking down. Its either, something in the circuit going open circuit, or worst case the engine. I still think it will be an instrument error of some sort and not the engine. What instrument are you using?

I second wlarsom861’s suggestion. Hook up a mechanical pressure gauge for a second pressure opinion. David W

You could also use an ohm meter on the sender as a pressure indicator while running the engine. The VDO 5 bar units increase in resistance about 10 ohm per 5 psi. That should tell you if the oil pressure is actually spiking or going open circuit somewhere else.
Steve
Sonex 892

[DCASonex]

The intermittent nature of your problem sounds like a faulty or loose connector, or broken wire or something that causes an open circuit. 80 PSI is the reading you will get with an open circuit. Would check entire length of wire from sender to your EIS looking for loose connectors, bad crimps, wire partially pulled out of a bad crimp, cold solder joint where wire connects to the multi-pronged plug, damaged wire where it passes any mounting point or through a bulkhead.

David A..