Fuel Flow Transducer going bad?

[dmat]

Hi all,

I have been having some weird reading on my EI fuel flow FP-5. At times, it shows zero while engine is running or it will sometimes read 14+. Could it be time for a red cube?

And the low fuel light is always on even if I am topped off. I think that could be because it wasn't calibrate? This was already installed with the airplane so I am second user.

Thanks,
D

[Jesse]

It have seen the. Go bad, but reading Low then reading High doesn?t make sense for a failing sensor. If 14 would be normal fuel flow, then dropping out periodically could be a bad wire connection or a failing sensor.

[Steve Barnes]

Mine would stop all together then work perfectly, then fluctuate, then work perfectly again (not in that order) Replaced with a good serviceable used unit. It seems to work OK, just needs recalibration.

Steve

[dmat]

Thanks Gents, I am going to look for any issues with the wires. If I don't see anything, I will replace with a cube.

I am planning on upgrading my panel to G3X so I might hold off as I will probably need a garmin sensor.

Thanks,
D

[airguy]

I had a similar issue once with mine - turned out to be a broken wire connection. The red cube sends out pulses to the EFIS box, and sometimes I would see no flow, or crazy high flow - the broken wire would either not be touching internally at all, or would be vibrating and making on-and-off contact at a high rate, which the EFIS would apparently interpret as a high pulse rate and display a high fuel flow rate. Once I fixed the broken wire all was back to normal.

[darata]

Connections, connections, connections. We always start there first. Out of curiosity, where is the transducer installed? Between the electric pump and the engine driven pump? If so, it should be moved to where it is installed after all fuel pumps. When installed between the pumps, we typically hear of erratically high readings. Loose connections can cause no pulses randomly, or can cause too many as the white wire may be intermittently grounding.

[dmat]

Thanks Dave. I have an idea where the connection is grounding.

[darata]

Let us know what you find. I'll be happy to offer any advice if necessary.

[lr172]

Originally Posted by dmat

Thanks Gents, I am going to look for any issues with the wires. If I don't see anything, I will replace with a cube.

I am planning on upgrading my panel to G3X so I might hold off as I will probably need a garmin sensor.

Thanks,
D

According to EI, the most common cause of red cube failure is wire connections and this matches your symptoms (intermittency). I would verify the wiring and re-crimp each connection FF.

Larry

[rv8ch]

Dave, quick question - do you see any issue physically mounting the transducer to the engine, or does it need to be "rubber mounted? The location is like Van's shows on the RV-14 - between the engine driven fuel pump and the throttle body, just under and to the left of the starter.