Oil pressure spikes and variances.

[lpaaruule]

Thanks for all the suggestions.

I'm using a GRT EIS 6000

GRT tech support said that it could also be caused by a failing ignition component causing noise. He said that he's had some customers that did everything right, and ended up having to use ferrite chokes to get stable readings.

The first thing I'm going to check when I get back to the hanger is the oil TEMP. The manual says it should never read below 59F, but I think mine was below ambient. I'll try it before even starting the engine. I know I was tugging on wiring, so I might have done something to that wire.

I've checked the wire going through the bulkhead, and didn't notice any chafing. I'm going to do a deeper dive, and start removing wire loom if as well.

Ugh...

[lpaaruule]

The good news is that the engine monitor appears to be working correctly, The bad news is that the temps were low on the EFIS because I had inadvertently changed the units to Celsius instead of Fahrenheit on the engine monitor, and the limits on the EFIS remained at Fahrenheit levels. I know my oil temp max'd out at 78C, which is 173F, but I don't remember what my CHT's got to; they had to be toasty. At least it was really cold out yesterday.

Anyway, the I removed all the zip ties, and wire loom, and followed the pressure sensor wire all the way from the engine monitor, and through the firewall. It and all the wires looked fine.

The fact that I didn't have any pressure spikes when I simulated the pressure sender with a 100 ohm resistor leads me to think that it's not a wiring, or noise issue.

So, that leads me back to my new VDO pressure sensor being the possible culprit. I had already ordered a Swift electronic pressure sensor from Aircraft Spruce, and now that I have all my wiring loose, I'm going to install that in the next couple days - hopefully.

[Rick524]

Might be interesting to test the pressure sender with an ohm meter and compressed air to see how it behaves.

[lpaaruule]

Back in the air!

I got the Swift oil pressure transducer/sensor installed a couple days ago. The EIS 6000 Aux settings are Scaling Factor: 61 (edit: tweaked to 65), and Offset 19 (which means -10). The excitation voltage line from the EIS 6000 was used to power the sensor.

Yesterday I did a ground run and verified that the sensor was responding/working. Once verified, I started the uncomfortable task of re-bundling all the wiring under the instrument panel, and fuel tank.

This morning, I got to the airport at 7am, and got all the firewall forward wiring bundled, and some other tidiness tweaks, and a couple ferrite chokes just in case. I was able to do a short flight just before bad weather set in, and so far so good, no pressure spikes.

The only drawback with using an oil pressure sensor on a different input than the default it that I can't set a separate, on the ground low RPM pressure limit. Not a big deal.

Thanks again for all the suggestions.

[WaiexN143NM]

hi all, paul,

ive reccomended the swift to a few others. i think it will last a long time compared to the vdo units. too bad you got a brand new vdo and it was faulty, and caused lots of more work.
glad you are flying again.

michael.

[builderflyer]

All the recent posts on the subject are timely. After over 15 years and over 700 hours of operation on the original oil pressure sender that came with my 20 year old engine, the oil pressure reading went a bit wacky on my last flight. Normal pressure at cruise runs about 52 psi but on this occasion, it repeatedly jumped up into the 70s and back down again. Given the age and hours on the pressure sender unit, it's likely to be the culprit but it's time to do some troubleshooting.

Art,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,Jabiru 3300 #261