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912is Low Fuel Pressure

in 912iS Technical Questions 10 years ago
I have been getting a low fuel pressure message after coming back from short rides.Pressure drops to 35psi when I pull the power back to idle on final,but goes back up if I add power,then back to low pressure when I go back to idle.I have replaced both the 10 Micron canister filter and the 62 Micron filter in the Gascolator. Both fuel pumps are on.
Whats going on???
Any ideas?
Steve

  • Re: 912is Low Fuel Pressure

    by » 10 years ago

    Hi Steve,
    I get the same thing happening. That is when going to idle, get a low warning.

    A couple of ideas...

    1) Check the volts/amps they are electric pumps and perhaps the secondary alternator that turns on at 2500 rpm + is switching off starving the pumps of power. I do not know for the rotax but standard EFI automotive fuel pumps can draw 6-8 amps each.

    2) I have tested standard fuel injectors a number of times and their flow does not drop off with pressure too badly, so long as the EGT's are not going high i cannot see it being a big problem.

    3) Is the "low pressure warning" setting a little too low, check it with the Rotax manual.

    4) Modern racing ECU's have inbuilt pressure flow maps and compensate by opening a little longer with low pressure. i do not know if the Rockwell collins unit does this, maybe someone knows ?

    Just a few thoughts

    Glenn
      
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  • Re: 912is Low Fuel Pressure

    by » 10 years ago

    check the fuel pressure regulator for contamination:
    Shut off fuel, bleed pressure by slowly loosening return fuel fitting on regulator, remove hose to airbox, remove snap ring, gently wiggle/lift regulator out of housing.
    Check for contamination in screen and seat area. see Heavy maint manual chapter 73-10-00

    fuelPressRegulator.jpg (You do not have access to download this file.)
      
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