From: "Finn Lassen finn.lassen@verizon.net" <flyrotary@lancaironline.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Fuel pressure trending lower.
Message-ID: <095eb14d-35a6-9080-79e9-e1c9c11553c2@verizon.net>
Date: Sat, 21 May 2022 10:30:30 -0400
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Recently I noticed my fuel pressure being low. Noticed because engine 
did not come up in power when advancing to full throttle. Noticed 
mixture real lean. Checking fuel pressure as low as 28 psi (normally 35 
and up to 40 at full throttle).

Going over my engine logs since first flight I now see that fuel 
pressure has been trending lower through each flight -- more pronounced 
on longer flights (40+ minutes). More and more pronounced over the 
months and became really noticeable over last month. Could explain why 
mixture tuning /appeared/ to have changed. Nice to have engine logs from 
practically each flight.

But why? Pump getting weaker?

My primary fuel pump is a GSL414. I figured it was wasted energy to push 
way more fuel than needed through the pressure regulator back to the tank.

My secondary (backup) pump is a GSL393. When turning that on, fuel 
pressure comes back up to where it needs to be.

Anyone have experience with failing or weak EFI pumps, particularly the 
GSL414?

Finn


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    <p>Recently I noticed my fuel pressure being low. Noticed because
      engine did not come up in power when advancing to full throttle.
      Noticed mixture real lean. Checking fuel pressure as low as 28 psi
      (normally 35 and up to 40 at full throttle).</p>
    <p>Going over my engine logs since first flight I now see that fuel
      pressure has been trending lower through each flight -- more
      pronounced on longer flights (40+ minutes). More and more
      pronounced over the months and became really noticeable over last
      month. Could explain why mixture tuning <i>appeared</i> to have
      changed. Nice to have engine logs from practically each flight.<br>
      <br>
      But why? Pump getting weaker?</p>
    <p>My primary fuel pump is a GSL414. I figured it was wasted energy
      to push way more fuel than needed through the pressure regulator
      back to the tank.</p>
    <p>My secondary (backup) pump is a GSL393. When turning that on,
      fuel pressure comes back up to where it needs to be.</p>
    <p>Anyone have experience with failing or weak EFI pumps,
      particularly the GSL414?</p>
    <p>Finn<br>
    </p>
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