Fuel Flow Sensor

[glennrv8]

I have an RV-8 with a D-10A and an EMS-10. Engine is an O-360. The plane has 55 hours on it and up until this point my Fuel Flow has operated normally registering 15 GPH on takeoff, and averaging 9.0 - 10.5 in intial cruise and throttle back. Today, I took off with the fuel flow registering as normal and about 10 minutes into the flight it went to 0.0, and then fluctuated between 0.1 - 0.4 for the rest of the flight. I lost percent power as well.

After landing I checked all connections and all seems fine. Any thoughts on what may have happened and what to troubleshoot?

 

[dynonsupport]

First guess would be that some sort of debris got in the sender and has jammed it.

Alternate theory is something in your engine changed and you now have the most efficient engine on the planet

 

[DBRV10]

Glen

Another thought, unless you live at high altitude, and you lean for takeoff, 15GPH is not enough fuel flow, unless you have only 150HP.

You should average about 1GPH for every 10HP at takeoff power at sea level.

You might want to check that out!

 

[N8RV]

Rather than start a new thread on the same topic, I'll just add to this one.

I also have an RV-8, with a D-100 & D-120 installed. First flight revealed a constant fuel flow reading of 10.5gph. Never moved.

I just did the fuel tank calibrations, and as I was taxiing back to the hangar, I noted that the fuel flow reading was 0.0.

I haven't started troubleshooting yet, and will start with checking the wiring. If everything checks out OK, what are the chances that I have a bad fuel flow sensor?

When I asked the rep at Oshkosh about the 10.5gph reading, he said that it shouldn't do that. It should either read 0.0 (if it's not working) or the correct fuel flow. Being stuck on any number isn't right.

Any help?

 

[dynonsupport]

Always a chance, though we don't see them fail very often in the field. Blowing very lightly through the sensor with air from your mouth and seeing if you get movement on the screen (when disconnected from the fuel line, of course) can give you a quick and dirty test to see whether the impeller is spinning in the device and registering with the EMS. And, given you're seeing no flow rate at the moment - checking the wiring as you've suggested is a good idea.

 

[acepilot59]

Your symptoms are exactly like mine except that I have about 300 hours on my EMS120 in my RV6. My meter is installed just down stream of the electric boost pump and before the gascolator. I agree that the most likley cause would be dirt in the tubine meter. Any thoughts on the best way to clean out the meter? Also is there any way to test the meter to confirm if it is contaminated?

 

[N8RV]

After a quick call to Mike at Dynon, I solved the mystery.  It seems that I followed the recommendation some months back to disconnect the keep-alive wire to the EMS.  I cut the yellow wire and, because I thought that there might be a day when it's recommended to reconnect the wire, I put connectors on the ends and tied them off.

Before calling Mike, I looked at the wiring diagram and the big plug that goes into the EMS and saw that there are THREE yellow wires in that plug!

Long story short, it seems that instead of cutting the keep-alive yellow wire, I had instead cut the fuel flow input wire!  Duh.  So, I connected the wire again and started the engine.  Normal fuel flow reading now.

Hope that helps somebody else.  DON'T CUT THE WRONG YELLOW WIRE!   :

 

[acepilot59]

My fuel flow is now reading low 3-4 GPH vs. 7-8 GPH after 400 hours of operation and no wires have been cut since the original instillation. This reduction in flow rate occured suddenly. I spoke to a friend with a Swift with a fuel flow meter and he suggested that it might be lead build up from 100LL fuel. He has used Hoppers gun cleaning solvent to clean out his Flowscan turbine meter and found what he described as lead balls after allowing the gun cleaning solvent to sit in the trubine meter for several hours, then dumping out the residue. Since the meter has slowed down and not stopped this explination seems to make some sense. Any comments?

 

[dynonsupport]

We haven't seen aging like that in general - we basically don't have any data that would point to that being a systemic problem. A low reading, assuming the K-factor in the EMS hasn't somehow been changed, would seem to imply that the impeller is spinning slower than usual though.