engine hesitation on take off

engine hesitation on take off

In a Cessna 150 the run-up went fine, completely normal, idling and taxiing at 1000 rpm. At the runway, upon smooth application of power, the engine hesitated going through 1400 rpm, and eventually stopped completely!

I then did a leaning run-up at 2100 rpm in case it was plug fouling, and then applied carb heat for a while just in case it had iced up.  Second time on the runway, same thing again (hesitation to the point of wanting to stop).

All other regimes on the ground were fine (mag check, idle rpm, carb heat function, etc.)  It's just the fairly direct application of full power that causes this hesitation.

Never happened to me before...does anyone have experience with this or ideas?

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Re: engine hesitation on take off

Hi Oscar;

Have your mechanic check the carburetor.  I had this happen and it turned out to be a worn accelerator pump.  When you rapidly open the throttle, there is a piston that pumps a shot of fuel into the carburetor to keep the air/fuel mixture correct.  If it isn't working properly, opening the throttle just lets more air into the intake, and the engine will hesitate or stall.  You usually don't see this on run-up as you open the throttle slowly and only go to 1700 or 1800 RPM, and the fuel flow change keeps up with the airflow change.

A second cause could be a dirty or blocked fuel filter or channel that is causing fuel not to flow at the higher RPM.  There is enough flow at the lower RPM but the higher RPM is causing the fuel/air mixture to go too lean.

One way to troubleshoot it would be to do your run-up to full RPM, slowly advancing the throttle.  If it will run at full RPM without hesitation, it is probably the pump.

Hope this helps.


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