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  #1  
Old 09-29-2022, 04:48 PM
nicoghilardi nicoghilardi is offline
 
Join Date: Dec 2021
Location: South San Francisco
Posts: 3
Default EFII system fuel pressure reading high

Setup is RV-14A with first generation EFII. This system has a fuel return line, and fuel pressure is regulated by an aeromotive fuel pressure regulator and monitored by a Kavlico 150 PSI sensor that sits on said regulator.

I have had issues with high indicated fuel pressures before and exchanged the sensor, which dealt with the issue. That was about 50 hours ago. Now, on my last flight, I observed again steadily rising fuel pressure, reaching as high as >70 by the time I landed. Engine ran perfectly fine, fuel flow normal. After I shut down, fuel pressure stayed >50 (?), so I pulled both fuel pump breakers and cranked the engine again so as to make sure there is no residual pressure in the system. It still read >50. My guess is that I have another bad fuel pressure sensor.

What I don't like about this is that the sensor is only about 50 hours old. Anyone else got similar experience? Ideas?
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  #2  
Old 09-29-2022, 07:03 PM
BoydBirchler BoydBirchler is offline
 
Join Date: Jul 2020
Location: Indianapolis
Posts: 196
Default

Measure the resistance and see if it is the sensor or lose wire connections. Klavico will list the resistance from high to low and what it should be at zero pressure.
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  #3  
Old 09-29-2022, 07:09 PM
BoydBirchler BoydBirchler is offline
 
Join Date: Jul 2020
Location: Indianapolis
Posts: 196
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Measure the resistance and see if it is the sensor or lose wire connections. Klavico will list the resistance from high to low and what it should be at zero pressure. The sensor is simply a resistor going to ground that varies its ohm value proportional to pressure .
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  #4  
Old 09-30-2022, 12:23 AM
nicoghilardi nicoghilardi is offline
 
Join Date: Dec 2021
Location: South San Francisco
Posts: 3
Default more info

Couldn't reproduce the problem today, so I went flying. At first, everything was normal. Then, after about 30 minutes, fuel pressure slowly starts creeping up gradually. At shutdown, with zero actual fuel pressure and the pumps off, it shows 11 PSI. So clearly, the sensor degrades over time. I will just replace it (again).
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  #5  
Old 09-30-2022, 08:03 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,732
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Quote:
Originally Posted by BoydBirchler View Post
Measure the resistance and see if it is the sensor or lose wire connections. Klavico will list the resistance from high to low and what it should be at zero pressure. The sensor is simply a resistor going to ground that varies its ohm value proportional to pressure .
The kavlico is a a tansducer NOT a resistive sensor, as most three wire sensors are. It has a microchip and gets 12V + GRD to power it and the chip sends varying voltages on an output lead to indicate pressure, usually from .5 at 0 to 4.5 volts at max pressure.

Larry
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 09-30-2022 at 08:11 AM.
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