Sonex Fuel Tank Calibration

[Murray Parr]

Hello all,

I am having the most frustrating time trying to get the Princeton fuel level probe to work (the one Sonex sells), I am able to calibrate it however, when I cycle the power it goes back to empty and you cant get it to read again unless you drain the tank and re-calibrate the module the same way as you would after trimming the probe.
The following is how it usually proceeds when I run the calibrations again:
Empty tank current tank raw reading is 88
15 litre current tank raw reading is1027
30 litre current tank raw reading is 1910
40 litre current tank raw reading was 2388 so I set 45 litres to be 2400 at which point I exited out of all the screens and turned off the power while I went to go get more fuel ( I checked with Ranier at MGL and he said I exited the screens correctly which should have saved all the settings).
When I came back and turned everything back on the tank read empty and the current tank raw reading was back to 88 even though I still had 40 litres in the tank (all the saved settings are still in the MGL IEFIS however the probe now reads empty (88) any time the tank is bellow 40 litres), I put the extra 5 litres in to make up the 45 litres total in the tank and the current tank raw reading moved to 292 (from 88) which indicates it is still working but has lost where empty level was at. The only way to get it reading correctly again is to carry out all the above again which I have done 4 times now with the same results.

Has anyone else had this problem and how did you resolve it. I was working with Todd from Princeton and i'm not sure he knows what is wrong with this one and I haven't received a responce for a few months now.

If I never turn the power off it would work perfectly but obviously that is not practicle.

[sonex892.]

Hi Murray. Can you enter the settings you recorded manually? I recorded the values when calibrating it in case I had to do it again.
Steve

[Murray Parr]

Hi Steve,
Yes I can enter them manually. The settings are always there in the IEFIS but the sensor seems to resort to the empty level each time the power is cycled off and back on. It's like the probe recalibrates itself to read empty again even if full

[DCASonex]

That sounds like a problem with the Princeton control unit. ask Todd to send you a trial replacement. If it works, old unit was at fault, if problem remains, return the unit and keep digging. He and GRT are some of the best folks i have encountered.

David A.

[Oshpilot]

Just spitballing here…
How old is the coin battery in your MGL instrument? I believe this is what maintains settings.

[Murray Parr]

Just spitballing here…
How old is the coin battery in your MGL instrument? I believe this is what maintains settings.

Battery is new and the MGL is keeping all the calibrated numbers.

[Murray Parr]

That sounds like a problem with the Princeton control unit. ask Todd to send you a trial replacement. If it works, old unit was at fault, if problem remains, return the unit and keep digging. He and GRT are some of the best folks i have encountered.

David A.

I'll keep trying to contact him, I figured he got busy with Oshkosh but still haven't been able to get a responce since early June. Maybe my emails are getting buried in spam or something. Getting a trial replacement will be difficult as the shipping to Oz might be as much as the unit to send it both ways but I don't see any other way to get it operating. Here is the last responce I got from him:

What are the three lights doing after you turn on power without pressing the button?

What were the lights doing while you calibrated the MGL?

Your only need 1S your readings were good.

I need to figure out why cycling power would have changed your results. It should not be possible. Makes me think the probe may be in the wrong configuration.

Do I have a picture of your circuit board? I can check my notes to see if I ever had a software bug that was ever released.

I do not think so, does not hurt to check.

Todd

I think he is onto something with the probe maybe not in the correct configuration as the 1S light is not what is flashing even after I re-configure it each time to 1S (it's the #2 light that is flashing but there is no advice on which light should be flashing for each mode. I think from memory the #1 light flashes after configuring to 1S mode but once power is cycled the #2 light flashes instead on my module).

[13brv3]

Todd retired and sold the business long ago, and a company called Red makes them now. I had a couple problems with my unit shortly after Red started making them, and Todd did reply from a motor home somewhere in FL. That was almost a year ago if I recall correctly, but he was helping with the transition.
Rusty

[Nick]

Hi to anyone still having issues or able to cure this issue. I read through all the threads from 10 years ago and more. I am having the same problem as everyone. I have a MX1 with the red Capacitive probe with the black box. I have done all instructions and I have an Email to MGL, no response yet. The MX1 readings are not moving as I add fuel. I have added up to 3 gallons and it still reads empty. I will try to put more fuel today and I read something about the ground needing moved so will try that today also. Any advice will help thanks
Nick

[Murray Parr]

If you change the mode (1S for example) you have to recalibrate (the calibration used when shortening probe) after the mode change. That is what I had to do after many months of frustration. It has worked fine ever since. You might also want to check out this link if that doesn't resolve your issue.

viewtopic.php?f=6&t=4365&start=20

has some other issues that others have sorted out.