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Engine Driven Pump


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Under Chp 28 IPC for my 77 M20J it redirects me to Chp 71-00-00 for the Engine Driven Pump but I can't seem to find it. IO-360-A3B6... Looking for a part #. My last flight it fluctuated from 25 then dropped to 14 psi at one point with no change in engine parameters or sound. After few seconds it shot back up to 24 but needle kept shaking. When I turned the electric pump on it shot to 26 psi and stayed there solid. Turned electric pump off it eventually settled to 24. Anything else I should be looking at? 

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Fuel pressure oscillation is the most unsettling of all things... (PP opinion...)

This is something to put in front of @M20Doc for input...

Looks like the mechanical pump is being challenged to make pressure...  it either is not producing enough pressure, or it could be leaking pressure that it built...

It is good to see the electrical pump being able to do its job properly...

Best regards,

-a-

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That fuel gauge looks like a direct mechanical gauge.  Over time the air in the line (which acts to dampen pump pulses)from the fuel servo to the gauge is replaced by fuel.  You can open the line at both ends and blow the fuel out then reconnect and see if it helps.  

As Rich points out air entry before the pump also happens, you can dribble a little 100 Wright oil down the fuel selector shaft to see if it temporarily seals the O ring.  If it does help the O ring requires replacement.

Clarence

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Try a leakdown test.    on the ground.   elec pump on.  open mixture.  Count to 6 alligators.  Mixture closed.  elec pump off.    If the pressures does not stay up for about a minute or so.  Mechanical pump is bad.   If you have fuel coming out of one of the three hoses in front of Pilot footwell. Your mechanical fuel pump is bad.

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Try a leakdown test.    on the ground.   elec pump on.  open mixture.  Count to 6 alligators.  Mixture closed.  elec pump off.    If the pressures does not stay up for about a minute or so.  Mechanical pump is bad.   If you have fuel coming out of one of the three hoses in front of Pilot footwell. Your mechanical fuel pump is bad.
Will do and report

Sent from my SM-G955U using Tapatalk

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On 3/4/2019 at 9:36 AM, lifendet said:

Will do and report

Sent from my SM-G955U using Tapatalk
 

No fuel out of hose front of Pilot footwell and pressure stayed for more than a min after electric pump was turned off. 

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