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No fuel flow indication

B

BigJohn

Well Known Member
No fuel flow indication - FT-60 sensor.

Today I did the carb snyc runs. Rotax came up to temperature and balancing went well. Good WOT runups too. All good except fuel flow reading was zero. The K factor was set at 96000, on recommendation of early flyers.

Tried reducing the K factor to 50000, no change.

Only thing I can think of is that I had forgotten to plug in the fuel pump fuse. Fuel was obviously flowing as engine was running fine. Could it be that the fuel flow sensor (red cube) gets its power through the pump circuit?

That's the only thing I can think of, since I had fuel flow indications on earlier engine runs.
 
Last edited:
BigJohn said:
Only thing I can think of is that I had forgotten to plug in the fuel pump fuse.

That's the only thing I can think of, since I had fuel flow indications on earlier engine runs.
Click to expand...

Was the fuse installed on earlier runs? If..... Yes. Then install the fuse and try the fuel flow again.
 
gasman said:
Was the fuse installed on earlier runs? If..... Yes. Then install the fuse and try the fuel flow again.
Click to expand...

Well yes, that's the obvious thing to do - but I won't have that opportunity for about three weeks! It's bugging me and I was hoping for an answer!
 
Flow transducer is independent

The Flow transducer is completely independent of the fuel pump fuse. The transducer gets its power directly from the the Dynon D-180 EMS pin 15 (12vdc). If the fuel flow was working at one time and the Dynon setup has not changed, then I would suspect either a bad connection or a bad transducer.
There should be continuity from:
Dynon EMS Pin 15 to the RED transducer wire
Ground to BLACK transducer wire
Dynon EMS Pin 14 to transducer YELLOW wire
Joe
 
Fuel Flow display

Hi John,
Is it possible you accidently toggled the fuel flow display option on the same setup page where the K factor is adjusted? I'm looking at page 6-14 of the installation manual.
I'm looking for a simple answer here because the only thing you recently changed was the K factor. The work on the EGT wiring was in a different connector than the fuel flow transducer wiring, so a mixup there is not a possibility.

Tony
 
Thanks Joe. That's what I suspected. Hope I don't have to pull that cover again!

Yeah Tony, I'm thinking along the same lines. Maybe I screwed something up in the setup - I hope! Bad news is I won't be able to check it until I get back, AND IT'S BUGGING ME!

Be on your coast later today, barring delays from the storm in Philly.

John
 
Hey BigJohn - -

Just a note. Mine quit working for a while. I think someone commented that it might be a speck of something that got into the sender and stopped the mechanism in the sender. I just flew it for a few times, and it started working again. Based upon that, I assumed it was a small piece of dirt. Just a possibility I guess. There certainly are tiny things in the tank that could go thru the tank wire screen.

John Bender
 
Back from vacation and .....

ran taxi tests today. Still no fuel flow indicated. Checked all the setup settings and all appears OK. I do have a question about that bottom setting labeled "Return". It is set to zero. Not much info about that in the manual.

Flushed fuel through the gascolator and no debris or water. Fuel pump chugging away just fine. Enigine runs fine with or without electric pump so I know fuel is flowing.

Does anyone know how to test the red cube? Should there be a certain resistance to check for across the sensor leads? I guess the next step is to pull the tunnel cover and have a look at the connections and maybe take some resistance readings.

Thoughts anyone?
 
Do NOT use ohmmeter

An ohmmeter will not give any useful information while testing a flow transducer. Who knows, an ohmmeter could even damage the electronics inside of the flow transducer. The red and black wires can be checked with a voltmeter to make sure that the transducer is getting power. The transducer puts out a square wave on the white wire when there is flow. It might be possible to tell if the transducer is working by comparing the voltage on the white wire when the electric pump is off compared to when the pump is running. Some more expensive voltmeters can also measure frequency and that would be a better test. The ideal test instrument is an oscilloscope.
Joe
 
The FT-60 is bad.

Thanks to all for the good suggestions. Today I pulled the tunnel cover and checked the FT-60 fuel flow transducer connections. All good. Checked power to red lead and ground continuity. Good. Then Bill came up with a good idea. He has an old flow transducer lying around, so why not clip-lead it into the circuit and try it? Viola! Fuel flow indication on the Dynon. Having thus confirmed a bad FT-60, I called Van's and ordered a replacement. If the weather cooperates, I will fly test hops next week without the flow meter, and replace the defective one when the new one comes in. Leaving the tunnel cover off for now.
 
Tunnel cover is structual

The tunnel cover is part of the airframe structure. Without the cover in place, the structure is weakened.
Joe
 
Thanks for the update

John,
Thanks for sharing your troubleshooting experience. It is good to hear that the problem has been found.
Joe
 
Replacement FT-60 arrived....

... and installed today. Problem solved. Bad transducer will be sent back to Van's for credit. Thanks to all for your ideas.
 
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