Low Oil Pressure

[vwglenn]

That's one of the pretty cool features of the MGL stuff. You can really dig in there and set it up according to specs. It lets you adjust the range, ohms, and the warnings. The VDO sender I bought is a 360-003. 0-80 psi with 10-180 ohms of resistance.

I was able to get an analog pressure gauge which plugged right into the npt port on the engine yesterday. Unfortunately I couldn't find anyone brave enough to stand 2 feet from the swinging prop to read it. I ended up safety wiring my phone to the engine and recording a short video while I hit the starter. The needle on the pressure gauge moved but didn't register. I couldn't bring myself to actually start the engine with my $800 phone strapped to it though. I reason that if it's making pressure with just the starter, there is certainly a possibility the current sender is having issues.

The good news is the engine is definitely making some pressure with just the starter and adding this new sender while knowing for sure what the specs are should allow me to eliminate the EFIS setup as a problem.

[sonex892]

Since you weren't sure what pressure rating the sender was, it sounds like your main problem was the probably MGL setting being incorrect.

Possibly a good thing to get rid of that ELO sender. They are a cheap copy of the VDO. I had 2 fail in the first 30 or so hrs on my engine. Replaced with a VDO and haven't had a problem since.

Steve
Sonex 892

[vwglenn]

New sender installed. Went through the MGL manual three times to see if I've done something wrong or missed something. Wire is good, dip switches in position, EFIS set perfect. 8-10 psi at idle (better than 3-5 psi I was getting from the old sender). I've checked everything I can possibly think of without breaking into the engine. Time to get in touch with Jab.

[vwglenn]

Well my pressure issue is fixed.

The main culprit was the old sender. It was certainly set up improperly on the EFIS (wrong pressure range). I also believe it may have been damaged as a close inspection showed signs of oil weeping from the seam around the bell. The damage may have been from the overfilled engine? That sender and its erroneous readings are what started this whole mess.

So why did the new and perfectly set sender show low pressure the other day? Well...I called Jabiru USA yesterday to get some advise and possibly an idea as to what the problem might be. Pete (super cool guy for helping a cold caller) gave me a couple things to check and one of them was to look for the chamfer on the washer holding the pressure valve in place. That was the first thing I did after I drained the oil again yesterday. Popping the relief valve back out was the key to finding the issue. Don't know how I managed to mess it up but I put the valve in backwards when I shimmed it the other day. Flipped it around. Re-installed. Topped off the oil. Now I'm showing 57psi at idle from the analog gauge with 6 ft hose I bought yesterday. Plugged the new VDO sender back in and its showing 58psi at idle.

Thanks to those of you who chimed in with ideas here.

[dtwolcott]

Glenn
That what they refer to as, for educational purposes, when you build your own. It to bad that when we make a simple mistake it takes a lot of study and trial and error to get to the education part.

[vwglenn]

I hear ya Don. I'm very meticulous about how I take things apart and, while I'm not 100% sure, I believe it may have been in backwards the whole time. What I am sure of is the original oil sender was set up 100% wrong in the EFIS and all of it is a teaching moment.

[vwglenn]

And It's back. Flew around for about 35 minutes yesterday. Had a great time till I pulled the power back on final and the oil pressure went below 11psi. :evil:

[snx590]

Hi Glenn,
I'm interested in the outcome...I fly behind 3300 #1574 which I have recently modified with new lifters, hollow pushrods and new rockers. What config do you have after the servicing at JabiruUSA? Also, what is your oil cooler and plumbing config/setup? I understand you are reading from the top port (post pump, pre-filter/cooler) location. I also have an MGL Enigma. The correct setup for a 360-003 gauge is 200 ohm and 80 psi. Since the gauge is calibrated within 10-180 ohms, at the low end the MGL is actually reporting psi a few pounds higher than actual, but close between 40-70 psi...overall no big deal since those gauges are not highly accurate anyway. (BTW - JabUSA supplies the 360-001 which has the M10x1 threads).
I also see a drop below 11 psi when oil hot and powered back to idle as shown in the attachement - the middle part was a stop and go at a nearby airport. I think what is more important is what pressure you are making at cruise....but confirm with Pete...I'd be interested in his opinion.

45 min flight w. stop-n-go

CapturePost.jpg (35.47 KiB) Viewed 8345 times

[vwglenn]

My Jab is a 3300A S/N 33A539. It was rebuilt in early 2014 after it locked up. All of the service bulletins were up to date after the rebuild. The oil cooler is the Sonex setup like this...

...and is fed through the sleeve between the filter and case. The MGL is perfect with respect to the settings for the oil sender. It is using the upper pickup. The pressure runs in the green at cruise power (somewhere around 40psi). Temps are in the green as well with the exception of a high EGT on #6 when climbing. CHTs look good too. When I first start the engine, the pressure is around 68psi. I had a 35 minute flight with one full stop Sunday. The full stop showed pressure in the green the whole time. Even while taxiing back to depart. It wasn't until I was on final for my second and last landing that the pressure dipped below 11psi. I talked to Pete a couple weeks ago. aside from the pump and the plunger, he said there's not much else to look for.

Talked to a local guy who knows a thing or two about electronics. He thinks the RDAC is getting hot and screwing up. So to eliminate that issue I'm going to get the pressure to drop again and plug a hydraulic gauge into the port to confirm the readings.

The only other thing I can think of which makes sense to me is the steel valve is expanding at a greater rate than the aluminium case or has a bur I missed and is getting stuck open as the heat builds.

[vwglenn]

So I'm absolutely certain the the sender is reading correctly. Verified against a hydraulic gauge.
PSI is 37-40 at cruise once warm.
Oil temps are in the green.

Email to Pete to see where to go next.

Terry
How much have you flown your plane in the condition it's in? I'm considering flying mine to Shelbyville (bout 1 1/2 hours) from my home airport.