Fuel Level dropping out

N941WR · #1 10-08-2016, 08:31 PM

For three years I was chasing a fuel level issue with my right tank and finally found and fixed the problem.

I would start up the plane and the EFIS would report the correct amount of fuel. Then, on some flights, while cruising along fat dumb and happy the right fuel level would drop down to zero, a few gallons at a time. Continue cruising and the level would come back up to the proper level.

I was 100% certain I had a bad ground wire. Multiple times over the past few years I have replaced the wires, checked the ground, etc. Every test flight indicated the proper fuel level and multiple times I was confident I had slayed this issue.

Then, on one flight, about an hour and fifteen minutes after I took off the fuel level dropped down, came back up, dropped down, etc. for the remainder of the flight. On the return flight, after an hour plus, the fuel gauge again started acting up.

Then it hit me, my capacitance sender (I purposely didn't give you all the info on my configuration until this point.) must be having an issue after it warms up.

A quick call to Dynon had a new sending unit in the mail. The next week found me back in the hangar installing the new sending unit.

After multiple long flights with the new sending unit installed, I'm happy to report that my fuel gauge is accurate and stable.

When I built my plane, the capacitance fuel level sensors was something I didn't know much about but after doing some research, I knew they were something I must have.

After nine years of flying with them, even with the intermittent issue I described above, I am always impressed at how accurate they are. If my fuel levels indicate I will need 10.3 gallons, the pump will stop on 10.3 gallons.

They are so accurate, that it was two years before I calibrated my fuel flow and to this day, I rely on the tank readings more than the fuel flow readings.

I realize that the capacitance senders will not read the same level with auto fuel and that's OK with me because I have yet to put any auto fuel in my plane.

When and if they ever come out with an unleaded alternative to 100LL, I will have to recalibrate my senders and that is a small price to pay for the accuracy of these things!

Mich48041 · #2 10-09-2016, 06:25 AM

Are there any capacitor type fuel senders that are self calibrating for any type of fuel or combination of different fuel types?

cajunwings · #3 10-09-2016, 08:59 AM

Bill: I would like to retrofit capacitance senders. I'm planning G3X panel. Which ones would you install today? How feasible is this retrofit on completed wings? (Wings are off at this time). Thanks

Don Broussard

RV-9 Rebuild in Progress

N941WR · #4 10-09-2016, 09:46 AM

Quote:

Originally Posted by Mich48041

Are there any capacitor type fuel senders that are self calibrating for any type of fuel or combination of different fuel types?

Not that I know of. The shape of the tank, the location of the installation, etc. all impact the way the levels are read by the senders.

To calibrate min, the SkyView (and the older D10 EMS) asked me to enter the fuel in two gallon increments. So, I calibrated two one gallon milk jugs using a measuring cup and marked the one gallon level with a Sharpe.

It wasn't that bad, just don't lose track of where you are. (I suggest keeping a note pad handy for each tank.)

N941WR · #5 10-09-2016, 09:50 AM

Quote:

Originally Posted by cajunwings

Bill: I would like to retrofit capacitance senders. I'm planning G3X panel. Which ones would you install today? How feasible is this retrofit on completed wings? (Wings are off at this time). Thanks

Don Broussard

RV-9 Rebuild in Progress

Don,

My capacitance plates were installed when I built the tanks; one plate on the outboard most rib, not the end plate. The other plate went on the inboard most rib. There is no way you can retrofit those without taking the rear baffle off.

That said, I see no reason why you can't make a probe type capacitance sender unit. The issue you will have is similar to the floats in that it will measure full until it starts being uncovered. That is unless, you can remove the tanks and put a second probe out on the end and tie them together outside of the tank.

Check your PM's.