Mystery Fuel Flow Dissapear

[RudiGreyling]

Morning Guys,

My fuel flow readings mysteriously disappeared, from one flight to the next. I downloaded the data onto a USB stick and there was a perfect fuel flow reading on the previous flight right up to the last second of shutdown, but then on this mornings flight after startup zero fuel flow reading. There was no erratic or low or high readings on the previous flights or data, Just perfect on the one flight and then dead on the next.

Q1) How do I trouble shoot this, without buying another expensive sensor?

The attachment show the engine running skyview sensor screen shot with Fuel flow showing zero.

Q2) What is the 9C01EBA number under C37 P14 Fuel Flow?

Thank you in advance.

 

[Garrett]

I would check the electrical connections 1st. If you have access to an oscilloscope you could verify output pulses during flow. Were the manufactures installations instructions followed?

Fuel Flow Transducer Notes
• NEVER blow through the transducer. Keep the yellow caps on until it is installed.
• The fuel flow transducer(s) should be installed in a straight section of your fuel line. (6 straight inches on each side is desirable).
• The fuel line should not drop down after exiting the transducer.
• The wires MUST NOT come out of the bottom of transducer. Wires pointing up is the best .
• When assembling fittings into the 1/4” NPT inlet and outlet ports do not exceed a torque value of 25 ft.-lbs.
• Do not use Teflon tape in an aircraft fuel system. Use “Fuel Lube/Ez Turn Lubricant”
• The transducer should be mounted down stream of a fuel filter.
• Do not attach the transducer directly to the engine to avoid excessive vibration.
• Do not mount the transducer near the exhaust systems or other hot engine components.
• If the transducer is in the engine compartment, it should be covered in fire sleeve to protect it from excessive heat.
• The transducer wires may be trimmed any desired length

 

[RudiGreyling]

OK Gents,

just to report back and close this topic...The Sensor failed pre-maturely on 250 hours....they suppose to last 10,000 hours ;-) or so the documentation say.

This sensor is fitted to a RV10 in the exact location the Vans plans suggest. In the cabin tunnel on the cold side of the firewall.

Fualt Finding:
I measured a good +12V and good Ground at the Sensor wires, eliminating good power and good ground as suspects.
Then I built a little 200hz square wave simulator to simulate the sensor and connected it at the sensor connection to verify my wiring and I got a nice fuel flow on my Dynon Screen. This proved either the sender is dead or the last 10cm of wiring into the sender is dead, but the rest of my wiring and Dynon system functioned correctly.

Then I took out the sender, awkward position working under the panel in the tunnel, then bench tested it, it was dead. I replaced with new sender and all is good.

Anycase I wanted to deconstruct the sender to see its internals. See below, it cannot be maintained even though there are screws on it. Everything is epoxied closed.

It looks like is a simple turning wheel construction with an Opto Electric LED and Light detector, counting the pulses.

NOTE:everything is epoxied closed, if you open it, you are going to break the wiring to the LED/Detector, then it will never work again. So it is NOT serviceable at All.

I hope that was interesting to some of you....

Kind Regards
Rudi

 

[Garrett]

Just curious what is the voltage peak to peak of your square wave simulator and thanks for sharing the pics.