High GPH Glitch

Plane had been sitting for 3 weeks, hangered, but in the bitter cold spell we were having. Subsequently, took a flight with the temp at 3 degrees F on the ground. G3X Touch system.

Did not pay attention to gph during takeoff (my bad) but noticed that it was reading at 25 plus when I switched to cruise. I am usually expecting 15 plus on takeoff and somewhat less than that in cruise (how much depends on how I am flying: ROP or LOP, usually the latter at around 7 gph). Tried turning the electric fuel pump on and off, which only made a difference in the fuel pressure. Switched tanks to no avail. Played with various throttle settings and the high gph was consistently high throughout the range of throttle. Same with the mixture, going from ROP to LOP. Actual fuel usage seemed to be as I was expecting (which I verified when the flight was over: 9.5 gallons used in 1.5 hours of flight).

I immediately landed and taxied back to my hanger. Before shutting down, decided to run WOT one more time. Now, it seemed to be reporting correctly. So, back into the pattern I went and everything looked good. Flew another 45 minutes with no issues.

Anybody have ANY clue regarding possible causes or even additional testing I might do to isolate the issue, assuming I can reproduce the issue at some point?

What type of fuel flow indicator are you using? Electronic red cube?

airguy said:

What type of fuel flow indicator are you using? Electronic red cube?

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Affirmative, Greg!

P.S. Tge engine was preheated prior to initial start (Reiff sump heater pads). Warmth verified personally.

Magic fairies installed 2 extra cylinders giving you 540 fuel burn for the first flight. The same magic fairies removed the bonus cylinders when you didn't thank them for their work.

Like all things computerized, sometimes "turn it off and back on again" fixes everything.

macrafic said:

Affirmative, Greg!

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The red cube operates by sending pulses down the signal wire to the receiving device. If you have a wire break or bad connection that is not completely broken, but continues to make/break intermittently, each contact is counted as a pulse by the receiving device. When the engine is running you may have a situation where vibration is causing the wire to make and break much more frequently than the normal pulses would come in, causing a much higher indicated fuel flow. In my case I found the wire break right at the entrance to the fuel flow transducer itself, but in practice it could be anywhere.

airguy said:

The red cube operates by sending pulses down the signal wire to the receiving device. If you have a wire break or bad connection that is not completely broken, but continues to make/break intermittently, each contact is counted as a pulse by the receiving device. When the engine is running you may have a situation where vibration is causing the wire to make and break much more frequently than the normal pulses would come in, causing a much higher indicated fuel flow. In my case I found the wire break right at the entrance to the fuel flow transducer itself, but in practice it could be anywhere.

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Thanks Greg. Sounds logical. When the weather warms up here in the frozen north, I will check the wiring between the red block and the fuel transducer. Until then, the fuel gauges are reading fine, fuel consumption is as expected, and I don't see any downside to waiting for the fix. Who knows, the fairies mentioned in a previous post may have made a permanent fix!!!