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Fuel flow during priming for engine start.

Asked by: 2114 views Aircraft Systems, Commercial Pilot, Flight Instructor, General Aviation, Private Pilot, Student Pilot

Good evening everyone,

 

This might be a sily question for you all but I became curious with engine priming and its fuel flow.

 

So when we prime the engine for start up(referring to C172S), we turn on the master and aux fuel pump and introduce mixture for few seconds and back to idle. Now the fuel after flowing throught the aux fuel pump, it flows down the linings of fuel system tomthe engine driven pump which is not working because engine is not running.

So my question is, does fuel still go through engine driven fuel pump, if not how does fuel enter cylinders for successful start up ?

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2 Answers



  1. EAD on May 05, 2016

    I would suggest reading Section 7 of the POH or Information Manual for the aircraft. They have a complete explanation and diagram of fuel flow.

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  2. crossaint on Sep 12, 2016

    The main fuel pump is of the diaphragm type, with an input and output check valve that prevent fuel flowing backwards to the tanks. These can easily pushed open by the auxiliary fuel pump.

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