Finn,
Once again the blind leading the blind, but it appears that wear and old age has gotten to your pump. I suspect that as with the second pump all is normal, then that excludes filter and water etc, just needs a replacement pump IMHO.
Easy when it is your money!
Neil.
From: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sunday, May 22, 2022 2:14 AM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Fuel pressure trending lower.
Do EFI pumps have an internal check valve? Dirty fuel filter?
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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