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Red Cube or EMS fault ??

pilotkms

Well Known Member
IO360 with Skyview. 150 hours. Started it up and fuel flow now indicates 0. Runup for preflight and engine runs fine but FF still shows ?0? at all times. No visual abnormalities with red cube or wires. Fuel pressure indicates normal - 25 with engine driven pump and 30 with electric pump on. Fuel is obviously flowing. Red cube doesn?t appear repairable. Do I change it and see if that?s the fix ?? Am I overlooking something simple or ez ??
 
Red cubes fail pretty regularly and I would suspect that. However, I would verify the connections first before declaring it dead.

Larry
 
IO360 with Skyview. 150 hours. Started it up and fuel flow now indicates 0. Runup for preflight and engine runs fine but FF still shows ‘0’ at all times. No visual abnormalities with red cube or wires. Fuel pressure indicates normal - 25 with engine driven pump and 30 with electric pump on. Fuel is obviously flowing. Red cube doesn’t appear repairable. Do I change it and see if that’s the fix ?? Am I overlooking something simple or ez ??

Most likely to be a wiring problem, and the FT60 is not repairable. If you open the unit there are set of tiny tiny wires embedded in epoxy that will shear, and now the unit is a paperweight.

First verify power and ground to the unit, then take the white "sense" wire and tap-tap-tap that wire to ground (frame) somewhere and watch your EMS. You should see some fuel flow indication, rising as you make-and-break that sense wire connection faster. The FT60 responds to fuel flow with grounded pulses through that wire, so if you're seeing pulses on the EMS when you fake the signal, then your wiring is good and the unit itself is suspect. If not, the wiring is suspect.
 
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Most likely to be a wiring problem, and the FT60 is not repairable. If you open the unit there are set of tiny tiny wires embedded in epoxy that will shear, and now the unit is a paperweight.

First verify power and ground to the unit, then take the white "sense" wire and tap-tap-tap that wire to ground (frame) somewhere and watch your EMS. You should see some fuel flow indication, rising as you make-and-break that sense wire connection faster. The FT60 responds to fuel flow with grounded pulses through that wire, so if you're seeing pulses on the EMS when you fake the signal, then your wiring is good and the unit itself is suspect. If not, the wiring is suspect.

The FT-60 is a transducer and most transducers send positive pulses on the sense wire. I have never tested mine on the bench, but would be surprised to see it not send positive pulses to the instrument.

Larry
 
Great info. Will test tomorrow. Will probably order one to be ready for the inevitable replacement now or in the future. Thanx guys.
 
The FT-60 is a transducer and most transducers send positive pulses on the sense wire. I have never tested mine on the bench, but would be surprised to see it not send positive pulses to the instrument.

Larry

You may be right on that - I know it uses an open collector output though. After thinking about the problem I had with mine, I remember now that I had a broken GROUND wire that was making/breaking intermittently. Each time it would make/break I would get an extra pulse on the sense wire and under exhaust pipe vibration frequencies (it's mounted on the cool side of the firewall just above the floor) I was seeing ridiculously high fuel flows for a short period of time, and then nothing when the wire finally gave up altogether.

I know that MGL Avionics specifies its use with a pull-up resistor, not sure how the other systems work?

EDIT - confirmed, it sends pulses of ground-voltage, with a floating voltage the rest of the time.
 
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The red cubes seem to fail prematurely when they are exposed to heat. I've been seeing quite a few of them lately in the engine compartment without any heat shielding. If you have it located there, and don't have some kind of heat protection on it, I would recommend you consider it.

Vic
 
Note: Never run the transducer wires anywhere near ignition wires. RMI from the ignition wires can transfer false pulses to the transducer wires, even if you connect the shield.
 
Just a note - -

The other style flow sensor I have been able to get working again with instructions from the vendor. Take it out and fill it half full of CARB CLEANER, and shake it a bunch and wash it out with gas or whatever, and maybe do that 3 times. It has worked for me. Not sure about red cube, but if it is bad, might be worth a try.
 
Replaced the red cube. Bought a new one from Dynon. started it up and Fuel flow indications are back in business. Will do test flite tomorrow. I have mine mounted to the side of the servo and hanging from the spider under the baffles. I added a 5/8? cooling hose from the right front intake. Maybe that will help this one last longer than 150 hours.
 
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