912is Low Fuel Pressure

by Steve Haulman in 912iS Technical Questions 9 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 Glenn Martin » 9 years ago

Glenn Martin

3 281 801

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 Rob Seaton » 9 years ago

Rob Seaton

3 1.32k 240

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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912is Low Fuel Pressure

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