G3X touch new fuel flow variation

[JimmyV]

At cruise, leaned in my SS fuel flow 6.8 gph with little variation, perhaps a tenth or two. Past couple of flights, fuel flow varying by 1 gph or even a little more - from 6.8 up to 7.8 or even 8, which i don't think is real, but an error in sensor or connection. EGTs CHT Rpms are all stable. So, fuel flow varying by 1 gph, with all else being equal. Any ideas?

Thanks

[Andy]

At cruise, leaned in my SS fuel flow 6.8 gph with little variation, perhaps a tenth or two. Past couple of flights, fuel flow varying by 1 gph or even a little more - from 6.8 up to 7.8 or even 8, which i don't think is real, but an error in sensor or connection. EGTs CHT Rpms are all stable. So, fuel flow varying by 1 gph, with all else being equal. Any ideas?

The reports I have seen on "red cube" flow sensor failure seem to be total failure or intermittent low reading. I don't know if it has a failure mode that would give a higher than correct reading. I would suspect a wiring problem.

One thing I would check is that connector P243 is securely locked to the GEA 24. It may be possible that intermittent connection of one of the 3 flow sensor pins is causing the GEA 24 to see more pulses than it should.

GEA 24 is mounted on the left side of the avionics shelf between the instrument panel and the firewall. P243 is on the top row of GEA 24 connectors and on the right side as you look at it from the pilot's seat. You should be able to check its security by removing the GDU 46x display unit. If you have never done that before just say and I, or someone else, can give some tips.

[JimmyV]

I pulled all quick connects apart forward of the firewall, cleaned and re-crimped as I have had other sensor issues due to the quick connects, and at the recommendation of Pete Dougherty at CC. This didn't seen to improve the matter. I've been thru the GDU hole in the panel before, but getting to the backside of the gea24 from the hole has been somewhat problematic for me in the past. I will give it a check upon return to the hangar, thanks!

[Andy]

I've been thru the GDU hole in the panel before, but getting to the backside of the gea24 from the hole has been somewhat problematic for me in the past.

You are not the only one who has cursed this installation. What is easy on the production line before the boot cowl is fitted becomes far harder on a completed aircraft.

If all you need to do is check connector security you may find a short hex key easier to use than a flat blade screwdriver.

[JimmyV]

went behind the panel, pulled the P243 and the plate, all connections at least appear to be secure. Re installed the connector, snugged it up with a hex - at idle still the fuel flow is moving around quite a bit. No apparent luck so far.

[Andy]

at idle still the fuel flow is moving around quite a bit. No apparent luck so far.

"Moving around quite a bit" could easily be a red cube sensor problem. You may need to review some recorded data to get a good baseline for normal fuel flow.

There are quite few reports that seem to indicate these sensors being far less reliable than claimed by the manufacturer.

[JimmyV]

a new red cube fixed the problem, thanks!

[jlezin]

I had similar problems with the red cube sensor and had to replace it. I'm told that gun bore oil can free up the spinner inside the cube. It gets stuck, possibly with lead deposits.