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  • Re: Fuel Flow sensor Install

    by » 5 years ago


    Should I run it and check the idle flow and WOT or can you tell by this there is install problem. Normally I have to turn the fuel injection computer on to get fuel to the engine and the return line to header.

  • Re: Fuel Flow sensor Install

    by » 5 years ago


    I just tried this procedure with the computer on same result 4.7.

  • Re: Fuel Flow sensor Install

    by » 5 years ago


    If you are displaying 4.7 with the engine OFF, what you are displaying is the Bypass Circulation Flow.
    3-5gph is about what the bypass flow will be.
    An unrestricted pump can move about 30gph.
    The 23 number is just the surge flow as the lines first become pressurized.
    This is to be expected and should settle out in a few seconds.

    You will probably also see 5+gpm with BOTH pumps running.
    The reason you can not get a reasonable display is likely that you are only displaying ONE sender and Not subtracting the other.
    You also might be Adding the two senders instead of Subtracting.

    Is the problem that you see 4.7gph Engine OFF, ≈5.2gph at idle, and ≈8-9gph at Cruise Power?
    If you subtract 4.7 from the display, the numbers would look correct.
    ZERO Engine OFF, 0.5 at idle, and 3-5gph at Cruise.

    What numbers do you see at idle and throttled up?

    The senders have a preferred direction of flow but that will not have any effect on the display.
    If a sender is installed in reverse, the measurement will be slightly inaccurate but it will Not indicate a reverse flow.
    The sender sends ≈68,000 pulses per gallon regardless of the direction.

    Unplug One sender at a time.
    What is displayed engine OFF and Engine ON?

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.


    Thank you said by: Robert Hannigan

  • Re: Fuel Flow sensor Install

    by » 5 years ago


    Ok thanks Bill I will fly tomorrow and record all the setting I get on the sensor and the dip stick readings.
    I will try unplugging the sensors tomorrow and let you know. AND hey thanks for all the help.

  • Re: Fuel Flow sensor Install

    by » 5 years ago


    You're Welcome! Don't be bashful about clicking the Thank You Button!

    I await the results. The 4.7 reading is a Red Flag that something is either misplumbed or misconfigured.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.


    Thank you said by: Robert Hannigan

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