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  #1  
Old 06-09-2018, 10:07 AM
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JackinMichigan JackinMichigan is offline
 
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Default Fuel Flow Quit Working

On last flight (20 hrs total) noticed the fuel flow reading quit. I have the "red cube" flow sensor, whatever it's official name. I assume everybody has the same.

Asking for your opinion. Is it most likely an electrical problem or could it be in the mechanical function of the sensor (or how reliable are they?).

My first test will be to disconnect a fuel line in the engine compartment and with the electric pump flow (rapidly) about 5 gallons thru the sensor to see if I can unstick it. Maybe use air to blow reverse air thru it.. worrying what harm that could do.

Any opinions guys??
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  #2  
Old 06-09-2018, 10:11 AM
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Auburntsts Auburntsts is offline
 
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Before you dive into disconnecting fuel lines, Iíd take a look at the wiring from the cube all the way to your avionics, particularly any splices along the way, to see if a connection has come loose.
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  #3  
Old 06-09-2018, 10:12 AM
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mburch mburch is offline
 
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Quote:
Originally Posted by JackinMichigan View Post
Maybe use air to blow reverse air thru it.. worrying what harm that could do.
Be careful... these things have tiny little bearings, and compressed air will spin them much, much faster than they're designed to turn in normal service. Probably better to blow manually, and gently. I'm talking less than birthday-candle strength.
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  #4  
Old 06-09-2018, 10:13 AM
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Yeah, what Matt said! Whatever you do don’t blow air into it. You be almost guaranteed to damage the cube if you do.
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  #5  
Old 06-09-2018, 10:22 AM
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JackinMichigan JackinMichigan is offline
 
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Default I agree

First, thanks for the warning about blowing air thru it. I won't.

I guess Todd's opinion is that it is most likely an electrical problem. That is my first inclination too. However, lots of work to get to the wiring connectors down in the tunnel. The fuel flow test is a lot easier to try first.
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  #6  
Old 06-09-2018, 10:36 AM
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JonJay JonJay is offline
 
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I have a Floscan, not Red Cube, but they make a simple tester for the FS. Perhaps they have a tester or have a way to check electrically?
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  #7  
Old 06-09-2018, 10:44 AM
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Auburntsts Auburntsts is offline
 
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Quote:
Originally Posted by JackinMichigan View Post
First, thanks for the warning about blowing air thru it. I won't.

I guess Todd's opinion is that it is most likely an electrical problem. That is my first inclination too. However, lots of work to get to the wiring connectors down in the tunnel. The fuel flow test is a lot easier to try first.
Itís not that I think itís more likely, just that in my mind itís the easiest first troubleshooting step. But I guess that depends on your specific installationó mineís slung under the engine between the mechanical fuel pump and the throttle body and is wrapped in fire sleeve so itís not easily accessible. Thereís no right or wrong, just be methodical and only test one variable at a time.
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  #8  
Old 06-09-2018, 11:37 AM
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JackinMichigan JackinMichigan is offline
 
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Default Got it Working

Did the fuel flow test and it's working again.

Don't know if I unstuck the sensor or the electrical gremlins blessed me just to keep me confused.

for your info, with an open fuel line the electric pump puts out 54 gph..
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  #9  
Old 06-09-2018, 11:45 AM
MConner MConner is offline
 
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Default Fuel flow changes with pump on.

My fuel flow increases by 2 gph when I turn on the fuel pump. This is a carbureted O-540. Any ideas?

Mark
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  #10  
Old 06-09-2018, 01:38 PM
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1001001 1001001 is offline
 
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Originally Posted by MConner View Post
My fuel flow increases by 2 gph when I turn on the fuel pump. This is a carbureted O-540. Any ideas?

Mark

Pulsation in the flow causing the Hall effect sensor to register double when the impeller reverses briefly?
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