REFLECTOR: FUEL PRESSURE PUZZLE

[Ron Brown]

That is indeed a head scratcher.  It sounds like the sensor is correct, but I agree, if the pressure is zero, then the engine won't be running - no pressure to the injector nozzles.  

Have you made any changes back there lately?  

Try this - disconnect the line going to the sensor and connect an air supply to it with a regulator.  Slowly ramp the pressure up to 30 psi, watch the EFIS  and see if perhaps there is a dead spot in the sensor.  I think these contain a variable resistor - like a slide wire - and perhaps there is a bad spot?????

Ronnie

 
  ----- Original Message ----- 
  From: Tom Martino 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Saturday, August 26, 2006 10:05 AM
  Subject: Re: REFLECTOR: FUEL PRESSURE PUZZLE


   
  The sensor is on the firewall and has worked great for 60 hours.

   

  -----Original Message-----
  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Ron Brown
  Sent: Saturday, August 26, 2006 7:04 AM
  To: Velocity Aircraft Owners and Builders list
  Subject: Re: REFLECTOR: FUEL PRESSURE PUZZLE

   

  Tom,

   

  You're right - that doesn't make sense.  

   

  Make sure the fuel pressure sensor is not mounted on the engine or otherwise picking up engine vibration.

   

  This sensor should be mounted on the firewall and be fed from a fitting off the discharge of engine's mechanical fuel pump.  There should be a restriction (small orifice - 1/16" or smaller) which should dampen any pulses to the fuel pressure sensor as well as limit fuel flow if the sensor or its line ruptures.

   

  Has it been acting this way ever since you started flying it or did this just start happening?

   

  Ronnie  

   

   

    ----- Original Message ----- 

    From: Tom Martino 

    To: reflector at tvbf.org 

    Sent: Saturday, August 26, 2006 2:17 AM

    Subject: REFLECTOR: FUEL PRESSURE PUZZLE

     

    Something is happening that I can't figure out.   My engine (IO-540) runs great . but the fuel pressure reading (EFIS One w/ resistive sender) goes down as I increase power.  In fact, at 2700 RPM . fuel pressure reads "0".  Obviously, I was getting pressure because the engine was running perfectly, but the reading was zero.

     As I decrease power, the fuel pressure goes back up to normal (28 - 30).

    I thought it was simply an instrument error . BUT . when I turn on the "boost" pump . during the low readings . the pressure reading goes back up to normal.  Turn the boost pump off and it goes down to zero.  So, the gauge is reading the Boost Pump but NOT the mechanical pump.

    What would cause my pressure reading to go down at higher power settings in an almost linear fashion?

    By the way . I checked the fuel venting and cleaned the fuel filter.  Everything is good on that end.

    Where do I begin?

    Tom


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