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Thread: IO-520 Fuel System

  1. #1

    Default IO-520 Fuel System

    Seems every aircraft with an IO-520 is a little different on fuel flow GPH in all power settings. Sometimes it is a guage off, injection system adjusted properly or improperly etc.
    My engine is currently in the process of overhaul, so when I install it of course I want it to be perfect.
    On takeoff I am just over red line on the fuel pressure guage. I usually cruise 24 squared or there abouts and 16.5 GPH gives me an EGT around 100 degrees rich of peak. Seems like I should be able to go more like 16 but the guage might be off.
    The manual gives specs for high end and low end pressures and how to adjust them.
    I would like to hear how others go about setting high end and low end.
    My guages are only a single channel EGT/CHT EI guage and stock guages.
    My dream is to have a full engine monitor with GAMI injectors but there is just to many other expenses this year.

  2. #2
    Member AK-HUNT's Avatar
    Join Date
    Apr 2006


    Pm sent

  3. #3
    Member algonquin's Avatar
    Join Date
    Feb 2007
    Seldovia, alaska


    AK-Hunt just sent the procedure I'm guessing , just my experience setting up the systems -you need good calibrated gauges, the right fittings ,no leaks, and two people. We do then fairly often, not hard when you are shown the right way. This isn't something to experiment with.

  4. #4


    What kind of fuel flow numbers are you guys seeing with what systems?
    I know thats kind of a loaded question as some run rich of peak ad some lean.
    Best I have done was 15.5 to 15.75 with GAMI injectors and engine monitor. That left 75 to 100 degrees rich of peak on the leanest cylinder.
    IO-520 cessna 206

  5. #5


    Here are a couple of photos of the throttle body off of an IO-520D '66 Cessna 185.
    I neglected to take any of the fuel pump where the pressure adjustments are.
    It is already out to the shop for overhaul.
    Attached Images Attached Images


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