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I discovered a work-around solution for the calibration problem when using the Princeton Fuel probe with the GRT EIS. The problem: When the system is calibrated for unleaded autogas and then leaded avgas is used, either wholly or mixed, the fuel level indication is grossly in error.

The fuel level with a full 16 gallons of autogas reads correctly as 16 gallons. This is the result of setting the GRT Aux1 (where the probe is connected on my system) scale factor (1SC) to 80 and then completing the calibration procedure on the Princeton signal conditioner per Princeton instructions.

This weekend I mixed 8 gallons of avgas with 8 gallons of autogas for a full tank of 16 gallons. The EIS read 10.8 gallons. I then calculated a new scale factor:

(16/10.8)*80=118.5

Inputting 119 as the new 1SC yielded a reading of 16 on the EIS with the mixed fuel.

At least yours works. I am on my second probe and have yet been able to get it to calibrate using auto gas. It reads a different value every time I turn it off and back on. It has been the only thing I bought for my sonex that I felt I wasted money on.

Keith
#554

david.2.wilcox wrote:
Inputting 119 as the new 1SC yielded a reading of 16 on the EIS with the mixed fuel.

Does it only read correct if the mixture is exactly 50/50?

My Princeton probe died when I introduced auto gas with ethanol. Killed. Dead.
When I pulled it, it was all corroded on the inside. Its simply not compatible with ethanol.

To add insult to injury, when I pulled it, it spun the fitting requiring me to use an opps fitting.

Same exact thing happened to my first one except it corroded so bad that it actaully broke at the joint between the brass plug and the aluminum tube. I only noticed it when I went to do a fuel flow check when getting ready to move to the airport and found that the finger screen was filled with bits of the corroded probe blocking it from getting more than a dribble out of the fuel line. I contacted sonex but they told me it was the first time they had seen this problem. Hearing your story it sounds like it isn't the first time it has happened though. Since the new probe doesn't seem to work reliably either I am considering pulling it out and putting in a fuel flow meter instead. I have pictures of the corroded and broken probe if anybody wants them to see what to look for.

Keith
#554