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Old 06-02-2010, 07:58 PM
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jasonlax jasonlax is offline
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Default N36sd

Several months ago, I wrote in inquiring about engine trouble at altitude. I have an O200, Ellison throttle body, LSE ignition & Mags. The trouble was engine roughness above 10000' or so.

The airplane has an electric fuel pump, which I asked about and several people indicated that it wasn't neccessary to fly with. So I left it off. Never used it. I flipped it on at 11000' a month or two ago - and the engine runs like a champ. What would cause fuel starvation at altitude? Pressure reduction? Now I flip it on above 10000' and have had no problems.

I would appreciate any comments or dialog about this.

-Jason
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Old 06-03-2010, 12:42 AM
Lynn Erickson Lynn Erickson is offline
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Default Re: N36sd

Quote:
Originally Posted by jasonlax View Post
Several months ago, I wrote in inquiring about engine trouble at altitude. I have an O200, Ellison throttle body, LSE ignition & Mags. The trouble was engine roughness above 10000' or so.

The airplane has an electric fuel pump, which I asked about and several people indicated that it wasn't neccessary to fly with. So I left it off. Never used it. I flipped it on at 11000' a month or two ago - and the engine runs like a champ. What would cause fuel starvation at altitude? Pressure reduction? Now I flip it on above 10000' and have had no problems.

I would appreciate any comments or dialog about this.

-Jason
The Ellison requires fuel pressure of 4 to 6 psi. They can run on gravity feed if they are configured properly for that operation. the gravity flow is aided by pressure in the tank from the ram air vents on the tank during flight. as you ascend the ram pressure is less. have you tried to throttle back at altitude when it is running rough to see if it smooths out at the lower fuel flow rate.
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Old 06-03-2010, 08:54 AM
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kjashton kjashton is offline
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Default Re: N36sd

Quote:
Originally Posted by jasonlax View Post
What would cause fuel starvation at altitude? Pressure reduction? Now I flip it on above 10000' and have had no problems.
I don't know what you checked before but I'd suspect a restricted vent or fuel restriction:
Blow into the vents and see if you have free flow into the tank. Remove/check the screen in the gascolator. Make sure you have good fuel flow into the gascolator (might need to install a fitting and hose to check that). Check the filter in the Ellison and any other filter in the fuel lines. I would also try to examine the tiny holes in the Ellison mixture rod.

There is less dynamic pressure into forward-facing vents at altitude. Could be that the lower dynamic pressure + a fuel restriction is just enough to trigger roughness.

BTW: It's good to turn on the Facet pump for takeoff and landing. It (1) backs up the mechanical pump and (2) insures the Facet pump is working
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Old 06-27-2010, 07:33 PM
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jasonlax jasonlax is offline
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Default Re: N36sd

During the conditional inspection, it was discovered that I have an automotive type fuel pump with a pressure regulator. They believe this is causing a minor fuel restriction only evident at higher altitudes. I have plans to replace the pump/regulator.
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