Erratic Fuel Flow Readings

[rv7guy2]

Need Your Help and Ideas !!!I have been having erratic fuel flow sensor readings on my EMS-120 since Day One! The readings jump between 0.0 GPH and 30 GPH continuously..sometimes sitting at 3.1 GPH for example for a while..which on my IO-360 fuel injected -190HP engine I know is wrong. Anyone else with a similar problem and/or a solution? I have changed fuel flow sensors without anything changing and have spoken with Dyonon Tech reps in the past without success. This issue is really bugging me as I cannot work the fuel computer without a stable fuel flow readings. The fuel content sensor and all other engine sensors work great!

Help !!

Dave
RV-7
C-GCPD

 

[tommuller2000]

I also have a problem with fuel flow readings, but it may be entirely different. I have an RV-9A with 320 hours on an O-320 engine. EMS-D120 fuel flow monitoring has been flawless until today and has tracked very well with fuel guage, dipstick and fill pump data. The sensor is in the cabin within a 18" of cabin heat, although covered with an access "doghouse" and carpet.

Last week we had rain and the hanger leaks a little. Then hard frost with daily temp ranges from 0-20 degrees F. I pre-heated the aircraft for today's flight and took off with an oil temp in the 80 degree range, but oil never got over 160 degrees. Shortly after takeoff, the fuel flow readings quit, although the engine never skipped a beat. I grabbed altitude for a potential dead stick landing, but the engine ran fine the whole trip. Switching tanks did not seem to help, although part-way to our destination, the flow reading came on again. On the return trip flow started OK then quit again. We noticed it cut in whenever we hit light turbulence and found I could induce it to run a couple minutes by jogging the stick for a short upward bump of about 2 G.

Is our problem frost or dirt in the line, a bad connection, or a bad sensor or something else altogether?

 

[PhantomPholly]

The fuel flow sensor can be sensitive to location and orientation.

For best results it should be inserted in a straight run (not immediately before/after a bend); not too close to the fuel pump; and some direction up (think it's referred to in the instructions). Some models are more susceptible than others.

Try searching Van's Air Force forums on "fuel flow".

 

[pittsdriver]

How timely. My flowscan unit worked perfectly for about 100hrs. Then it would get erratic and shut down. I have gone through all of the wiring and it would work for awile then shut down again. I just put a Red Cube transducer in and it worked about 5 min then went erratic and shut down. All I have gotten from Dynon is you must have a bad ground. The rest of the info on the EMS works perfectly and I have never had any issues other than the fuel flow/totalliser. I will try grounding the black wire directly to the ground buss. Don

 

[PhantomPholly]

Hehe - you have no idea how much time I had to spend getting grounds perfect in my 18 year old second-hand plastic airplane!

I haven't had any troubles with the fuel flow yet, knock on wood. But until I got the grounds right I had plenty of other problems.

 

[jakej]

"My flowscan unit worked perfectly for about 100hrs. Then it would get erratic and shut down. I have gone through all of the wiring and it would work for awile then shut down again. I just put a Red Cube transducer in and it worked about 5 min then went erratic and shut down."

Pittsdriver
IMO, from the symptoms, the cause is in your plane - not the fuel flow units IMO

Jake J

 

[pittsdriver]

Found the problem. I was always looking at the ground wire for the problem but it was the power wire. Was loose in the molex connector at the cannon plug. I wired the power directly to the circuit breaker and ground to the ground buss it works perfectly now. Don

 

[tommuller2000]

I'm puzzled, power wire? Doesn't the flow sensor get its power directly from the EMS-D120? Its been three years since I had this open, so I may have forgotten.

 

[dynonsupport]

The fuel flow senders require +12V. We output that from the EMS, but it's possible to just use the +12V from the airplane as well. Either works, but we do prefer using the EMS output so that's what we document in our install manual.