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Thread: Fuel Pressure sender failure

  1. #1

    Fuel Pressure sender failure

    Pre-flight, start-up, and run-up were all normal...as were take-off and climbout to 2500' during the southbound turn...including turning off the boost-pump.

    After levelling off, throttling back, setting the prop and mixture, I got a 'check fuel pressure' warning from my AF3400EM engine monitor. Quick scan showed I was still flowing 12 GPH throught the flow meter and the engine purred along just fine - with the pressure at zero PSI! That didn't make sense, so I fired up the boost-pump - now the pressure is fluctuating between 6 and 7 PSI - everything else is fine. During the remainder of the trip back I checked various throttle, prop, mixture, fuel-tank selection and boost-pump settings to see what changes things. The only change inducing event is the boost-pump which presents as fluctuating 6-7 PSI while on.

    Landing and rollout are uneventful as was taxi back and shutdown.

    Post-flight examination and testing showed proper fuel pressure (approx 32 PSI) with boost pump running and purge valve selected on the ground with engine not running. There was no fuel leakage at any of the fuel system components. Wire wiggling showed the single fuel pressure sender wire was intact and tightly captive on the stud - however the stud assembly wiggled a bit within the sender body. Comparing this to the oil pressure sender mounted right next to it told me something wasn't right. The pressure sender is mounted on Vans manifold on the upper part of the firewall. The manifold is mounted with a spacer to allow the combination oil-pressure light / Hobbs meter activator to clear the firewall. There is a little curve in the wire to allow for movement. The flow restrictor is installed in the 45 degree fitting attaching the pressure sender hose.

    Has anyone else experienced this failure mode? If it is common, then I would look at the sender quality. My concern is the installation may induce vibrational stress to the internal sender components. I can change my spacer which should change the harmonic frequency of the assembly.

    Here's a picture of my installation taken as I was building.Name:  P9160003a..JPG
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    Thanks,
    Ralph

  2. #2

    Update!

    The folks at Advanced Flight Systems are sending me a different brand (VDO) sender instead of the original Stewart-Warner style. It is supposed to be a little cheaper too. All I need is the software instructions for the different style....

    I'll post another update after installation and some flight time.

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