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Asked by: 3566 views Aircraft Systems, General Aviation

situation) because i failed starting engine, i thought it may caused by lack of injection.

so i did over-priming to inject fuel.

what over-priming lead to ?


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4 Answers

  1. Carl Tyler on Mar 12, 2013

    Overpriming leads to a flooded engine, which can lead to a backfire if you’re not careful.

    Follow your flooded start procedure.

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  2. Bill Trussell on Mar 12, 2013

    Priming is used to put raw fuel vapor into the clinders in order to initiate the start of combustion in each clinder. Over priming is another term for putting too much raw fuel in the clinders. The idea is to put vaporized fuel in, not liquid. Over priming also washes oil off the walls, negatively impacting lubrication.

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  3. Namugoni on Mar 13, 2013

    thank you sir.

    what about airplane without primer?

    such as TB-9, she doesn’t have a primer.

    we do inject fuel by only using throttle.

    over injection using throttle, same problem occurs?

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  4. David Brown on Mar 13, 2013

    If you have over primed, using a WOT and cranking clears this.

    In a carburetted Lycoming the simplest method of starting is not using the primer at all. While cranking use full sweeps of the throttle with the mixture full rich. They generally fire in the first two sweeps.

    In a fuel injected engine, and lets assume a Lycoming such as the IO360 the proceedure is this.

    WOT, Mixture full rich, boost pump on count to three (1 and 2 and three and) > pump off
    Mixture back to idle cut-off. Throttle closed, then crack open enough to be equivelent of 1100 RPM.
    Crank the engine and as soon as the engine coughs roll the mixture in progressively.

    This next bit applies to carburettor and injected engines;
    Once started and settled, set the throttle at about 950 RPM, then lean the mixture to just past max rpm, which may be around 1050, but it really is not that critical, just avoid idling at more than 1100 for noise, stone damage etc.

    TCM/CMI’s thats another story!

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