Fuel flow (red cube sensor) reads 0 during flight. Any ideas?

[ao.frog]

Hi folks.

During a flight yesterday, I noticed that FF indication on the AFS 4500 intermittenly where reading 0. Since it was not dashes but 0, I assume that it was the red cube who where sending a false signal to the 4500.
The engine was running normal the whole time, with normal EGT and CHT indications.

Reason for the assumption is that I think I remember from the install, that when the 4500 does not receive any signal, the corresponding line reads dashes.

During the rest of the flight (15 mins in a straight line back to my home field), the FF intermittenly showed normal indications, but mostly 0. Never any dashes.

This weekend I'll check all connections and lines to see if I can find anything wrong. If not, I guess a new red cube is the only way to go.

The engine, a stock Lyc IO-360, the the 4500 and the red cube was installed in 2012, first flight 2014, and TT is now 240 hrs.

Has anyone experienced a red cube indication failure after 240 hrs? Or is it something else going on here?

[noelf]

I have had similar indications on my 0-360. I have a carb setup. If I do not lean the engine, the readings are what I would expect. When I run at 2400 rpm, and lean the engine out...that is when I can see 0 gph and then it goes up to 4 or 5 gph and then back to zero. Repeat / repeat/...

I tried to noodle this out and the best I could come up with is: the carburetor floats are moving up and down in the float bowl. When the bowl is full there is zero fuel flow. As the bowl empties and the floats lower, then fuel flows and the red cube indicates fuel flow. That is my best guess.

[Larco]

Sounds like you both need to check the connectors but most likely replacement of the red cube is the fix. BTW, when mine did this it took a new unit to fix and I found AFS or Dynon the least expensive vendor. Another BTW, a few friends have had the same similar issue and a replacement of the red cube was required.

[pilotkms]

My first lasted 150 hours. Its located beneath the baffles hanging down from the spider after the servo. I put a cooling blast tube on the new one, thinking heat may be its downfall. I Just replaced my second one after 250 hours. It was 13 months old so past the 12 month warranty. Not sure if they?d cover it anyway. I consider it a recurring maintenance item for now. Less than a dollar per hour. Flying too much to think about changing its mounting location.

[kaweeka]

I've been wrestling with strange ff readings with my IO 320 utilizing the Red Cube. I've replaced wiring, sent it to EI who swears it checked out with both water and fuel, had my injection system checked out by AFP and replaced the hoses. Still gives wonky readings at times. Had Savvy double check my data, too! I may look for a different totalizer since I didn't have this trouble with the FloScan. Hmmmm.........

[FasGlas]

I've been fighting with Red Cube intermittent readings for many years. I've checked and / or replaced everything I could think of, including 3 Red Cubes. I've now moved my factory tested Red Cube from the servo to spider location to the gascolator to boost pump location. The techs at EI claim the readings will be accurate at this location. So.. I'll see on my next flight.

[darata]

Originally Posted by pilotkms

My first lasted 150 hours. Its located beneath the baffles hanging down from the spider after the servo. I put a cooling blast tube on the new one, thinking heat may be its downfall. I Just replaced my second one after 250 hours. It was 13 months old so past the 12 month warranty. Not sure if they?d cover it anyway. I consider it a recurring maintenance item for now. Less than a dollar per hour. Flying too much to think about changing its mounting location.

It would've been covered under warranty. Never a bad thing to ask. Matter of fact, if you provide me with the serial number, I will be happy to look it up. If it does fall under our warranty, send it in to us. If we verify that it has failed, I will send you a replacement at no cost.

[RV-4]

Well I guess that I'm now part of the erratic Red Cube Readings club...

I had the same symtoms over the last couples of months but was too busy flying to have a look at it..

Well 2 days ago, I finally got to work on it and replaced my 5-6 years old Red Cube with a new one...

Initial run up reading appears to be spot on but I will fly the aircraft tomorrow and will check the readings...Fingers crossed..

I also wrapped mine in Fire Sleeve just to shield it a little better eventough I don't think heat was the issue here..

Bruno
rv4@videotron.ca

[ao.frog]

Thanks for the replies folks. Ok, so it seems like it'll be a replacement then. NOT impressing regarding the service-life of the red cube though... oh well, I'll contact Rob and his exellent crew tomorrow and buy a new red cube from them.

Too bad that it'll take at least two weeks to get it over here, and of those two, at least one week will be in the Norwegian customs and domestic postage.

I'll report back after the replacement and testflight.

BTW: it's mounted on the FF, just after the fuelpump, so it's not exposed to vibrations and heat. From there. the fuelhose goes to the injector.


Before the failure, it has shown VERY stable and accurate FF indications.
Thus, the total fuel in the tanks shown on the AFS-4500 has been within 2-5 litres of the actual remaining fuel amount every time I have fully filled up the tanks.

So up until now, I've been VERY impressed both by the 4500 and the red cube.

[vic syracuse]

We replace quite a few of these that fail in 100-200 hours when they are not heat wrapped in the engine compartment.

Vic