No % power or Fuel Flow readings

[rockwoodrv9]

I was headed to Mackinac Island this morning and as I was leaning the engine I noticed there was no % power or Fuel Flow indicated on my G3X. Everything was working fine including EGT and engine was running great but I came back to the hangar. I looked at everything on my VPX power system and no faults.

I’m just now taking the cowl off to check wires but I just inspected everything about 3 hours ago when I did oil change. I don’t know enough to know if this is a grounding issue or just having less info than most planes had for many years until such advanced instruments came into play.

Any ideas or known issues with the Red Box I should look at first?

 

[rockwoodrv9]

I checked all the wires - nothing looks loose. Everything at the VPX looks good.

I just now thought maybe something in the g3x setup could have changed? I will check the config pages on the g3x. Any other ideas?

 

[Untainted123]

I doubt something would randomly change in your settings for the G3x, unless you were in there playing with something. It looks like just your fuel flow readings were affected, which makes % power no longer available:

Middle of page 618 of the G3X/G3X Touch Installation Manual

https://support.garmin.com/support/m...o=010-00G3X-00

"Estimated engine power can be calculated for Lycoming and Continental engines, using inputs from RPM, Manifold pressure, and Fuel Flow sensors (All three are required for engine power calculations)."

I would investigate your connection to the red cube, and any grounding issues. Or perhaps your FF sensor has failed.

You could also download the logs from the G3x and look for anything erratic in there, and to confirm when you last saw correct readings for % power and fuel flow.

 

[rockwoodrv9]

I must have stressed the connection when I did my oil change last week. I talked with Midwest Panel Builders and they said it was not likely it just crapped out so I will recheck the connection.

Midwest Panel builders is close to me and they have been really helpful and I didnt get my panel from them. Im going to take my plane over after AV and have them check all the settings and configuration for everything. The build all the Sling panels.

I doubt something would randomly change in your settings for the G3x, unless you were in there playing with something. It looks like just your fuel flow readings were affected, which makes % power no longer available:


I would investigate your connection to the red cube, and any grounding issues. Or perhaps your FF sensor has failed.

You could also download the logs from the G3x and look for anything erratic in there, and to confirm when you last saw correct readings for % power and fuel flow.

 

[RV7A Flyer]

I must have stressed the connection when I did my oil change last week. I talked with Midwest Panel Builders and they said it was not likely it just crapped out so I will recheck the connection.

Why are they so sure? I had one do pretty much exactly that after something like 600 hours. One day fine, next day, a bit jittery for a few minutes, then, stuck at 0 gph.

Did you FF show 0, or did it go offline entirely?

 

[rockwoodrv9]

Why are they so sure? I had one do pretty much exactly that after something like 600 hours. One day fine, next day, a bit jittery for a few minutes, then, stuck at 0 gph.

Did you FF show 0, or did it go offline entirely?

Both showed 0. Percent power was "0%" and FF was "0"

Im grasping for reason it stopped working. Im going to download the last few flights and see if it happened in flight or between flights.

 

[RV7A Flyer]

Both showed 0. Percent power was "0%" and FF was "0"

Im grasping for reason it stopped working. Im going to download the last few flights and see if it happened in flight or between flights.

You don't say what kind you have, but for mine (the red cube, FT60), it seems fairly common for the impeller to eventually quit, um, impelling. It just gets stuck and thus reads 0 flow (but since it only has the vanes sticking partway into the flow, it doesn't block any fuel flow if it fails).

Do a search here for FT60 or red cube failures.

 

[mburch]

Based on my experience with this system I would expect to see 0% for calculated power if the fuel flow gauge shows zero. The advice above to look for loose wires (power, ground, and signal) or a misbehaving sensor is what I would recommend also.

 

[rockwoodrv9]

You don't say what kind you have, but for mine (the red cube, FT60), it seems fairly common for the impeller to eventually quit, um, impelling. It just gets stuck and thus reads 0 flow (but since it only has the vanes sticking partway into the flow, it doesn't block any fuel flow if it fails).

Do a search here for FT60 or red cube failures.

Thanks. I will search it out. Here is a picture. Thanks for the help.

 

[rockwoodrv9]

Lots of Problems found searching

Im not sure how I was under the impression that the Red Cube was indestructible and always worked perfect but there are lots of reviews showing it crapps out about 140 hours. Mine has about 200 hours so maybe it is toast. That is $1.00 per hour. It has been very accurate and I am OK if that is the lifespan - I just wish the info from the manufacture told me so I could have one on hand.

I will make sure the wiring is easier to replace this time and order 2!

 

[RV7A Flyer]

Im not sure how I was under the impression that the Red Cube was indestructible and always worked perfect but there are lots of reviews showing it crapps out about 140 hours. Mine has about 200 hours so maybe it is toast. That is $1.00 per hour. It has been very accurate and I am OK if that is the lifespan - I just wish the info from the manufacture told me so I could have one on hand.

I will make sure the wiring is easier to replace this time and order 2!

I don't know about 140 hours...that doesn't seem accurate at all.

I don't know what the MTBF is on it, but yes, there are reports of *some* failures at several hundred hours (in my case, e.g., 500-600 or so, don't remember exactly). But a handful of anecdotes doesn't make for actual statistics, so I'd be pretty skeptical of "140 hours".

That said, my money is on a failure of your red cube...it's still connected and sending data (so no highly erratic values or out-and-out dropouts), so probably *not* a connector or loose wire, but it's just sending 0 as the data, continuously. Sounds like a stuck impeller to me.

Let us know what you find.

 

[BillL]

Rock, the photo shows the cube sitting over the exhaust pipe - a shield might be a good idea. Also, when you remove it, put a cap (aluminum foil) over the connections and on the bench, carefully see if there is FOD in the inlet. DanH has the flow passage as .141" vs the .340" of the fitting. Still could be a connection, but it appears you used a high reliable DT connector.

 

[MacCool]

Im not sure how I was under the impression that the Red Cube was indestructible and always worked perfect but there are lots of reviews showing it crapps out about 140 hours. Mine has about 200 hours so maybe it is toast. That is $1.00 per hour. It has been very accurate and I am OK if that is the lifespan - I just wish the info from the manufacture told me so I could have one on hand.

I will make sure the wiring is easier to replace this time and order 2!

Mine crapped out at about 400 hours. I had intermittent and variable fuel flows...%power also was off line when the red cube went to zero.

..

 

[RV8JD]

Red Cube

I guess I'm lucky (and/or the builder did a good job on the installation). 1370 Hobbs Hours on my RV-8 and it's still going strong.

 

[mburch]

it's still connected and sending data

I would be hesitant to make this conclusion based on the reported observations. In my experience with this system, a failed fuel flow sensor will produce identical results on the avionics display as either an open circuit, a dead short to ground, or a sensor that is not receiving power. Before replacing the fuel flow sensor, I would verify continuity of the wiring all the way from the sensor to the GEA 24.

 

[RV7A Flyer]

I would be hesitant to make this conclusion based on the reported observations. In my experience with this system, a failed fuel flow sensor will produce identical results on the avionics display as either an open circuit, a dead short to ground, or a sensor that is not receiving power. Before replacing the fuel flow sensor, I would verify continuity of the wiring all the way from the sensor to the GEA 24.

Ah, good point. I was just thinking of *my* installation, a Skyview, where these things would likely lead to either a wildly changing signal/displayed value, or a red X due to no signal. You're absolutely right, though...first thing to check is wire continuity and security, especially at connectors.

 

[lr172]

I would be hesitant to make this conclusion based on the reported observations. In my experience with this system, a failed fuel flow sensor will produce identical results on the avionics display as either an open circuit, a dead short to ground, or a sensor that is not receiving power. Before replacing the fuel flow sensor, I would verify continuity of the wiring all the way from the sensor to the GEA 24.

Possibly. Red and black wires power the cube. The white is open if the unit is not working OR if working and the notched wheel is blocking the light source (it is an optical unit). EMS sends a biased voltage on the white wire. If the transistor is open (default state), it reads no voltage. When the cube closes it to ground (which happens when the photosensor detects light through the notches on the wheel), the EMS sees a voltage. Typically each pulsed voltage (square wave) is around 1/68000's of a gallon (K factors sets that fraction). Therefore it could be several things, including a failed cube. Unsure if or how an EMS would detect an error, as it is really only looking for a closed circuit pulse and counts them.

You can take the EMS wire going to the cubes white wire and rapidly touch it on and off a ground source and the EMS should show positive flow. That would tell you the sense wire up to that point and the EMS are good. Red and black can be tested with a VOM.