Engine Driven Fuel Pump - Diagnosis

fjpoolefjpoole
in General Discussion
Need some help - Have a Turbo Lance II - TIO-540-S1AD -

Flying the other day and suddenly started losing power in flight - turning on the electric fuel pump seemed to solve the problem. After landing engine ran rough without electric fuel pump on - switched fuel tanks - no difference.

I thought I would have to replace the mechanical fuel pump...

Took it to the mechanic today - and wouldn't you know - runs great - ran it up several times - took off and flew around for an hour, with and without electric pump.

SO my question is - can a mechanical fuel pump have an intermittent problem? Should I replace the mechanical pump anyway (my mechanic said he wouldn't).

Not trusting the plane completely at the moment - any advice as to what might have caused the issue and how to proceed?

Thanks for the help in advance....

Comments

  • bigandybigandy
    I seem to recall an AD for a repetitive inspection (every 50 hours) on the torque of the Lear Romec engine drive fuel pumps to verify that the seal of the gasket was good. This was a result of a couple of planes having fuel leaks inflight. Kelly Aerospace produced a different gasket which mitigated some of these issues. This is described in this article by Kelly:
    http://www.kellyaerospace.com/articles/Romec_AMT.pdf

    When I was faced with the AD - I chose to swap out my engine driven fuel pump to a new design Kelly Aerospace one - you can find the appropriate one listed here:
    http://www.kellyaerospace.com/fuel_charts/Fuel_Pumps/Fuel_Pump_App_Chart.pdf

    However - I am referring to compliance with a fuel pump gasket AD and not directly related to what you were experiencing. If you read the first link which describes how the fuel pumps are designed, then it might relate to you, perhaps, experiencing some fuel contamination, which in turn caused some clogging of the pump. When you turned on the electric pump, the bypass fuel circuit allowed a good flow to the engine.

    Since the fuel system is not that complicated on the PA-32's - perhaps a complete look at the components wouldn't harm. The fuel tanks could be checked for debris. The fuel selector valve (a topic of previous postings) might be worth checking - there is a screen that can be inspected for debris too. The fuel servo should also be considered - since I experienced some issues with rough engine starting - and this was from a servo that was overhauled by the engine builder. My troubleshooting allowed me to swap to a known 'good' fuel servo which mitigated the problems. When the 'bad' fuel servo was finally inspected by the overhaul company they found a diaphragm/bellows failure (which they claim is very rare) - however this accounted some rough engine starts and over rich settings.

    In summary - I would start at the fuel tanks and work your way in. My experience was with the fuel servo, the fuel selector valve and the engine drive fuel pump.

    Good luck.
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