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-   -   C172 fuel injected engine procedure (https://www.pprune.org/private-flying/643902-c172-fuel-injected-engine-procedure.html)

shumway76 24th Nov 2021 14:32

C172 fuel injected engine procedure
 
With the C172R and S series which uses the fuel injected engines, the engine starting procedure is basically:
- prime (aux fuel pump on, mixture rich until fuel pressure stable 3 to 5 secs, mixture cutoff, aux fuel pump off)
- mixture cutoff position
- ignition start
- mixture full rich once engine starts

However, in the emergency procedures per POH, for in flight restart due to engine failure, the steps are basically:
- aux fuel pump on
- mixture full rich

So my question is, how is it for normal start, mixture is in cutoff position but in-flight restart it's in full rich?

Fl1ingfrog 24th Nov 2021 21:32

Hello shumway76 no one seems to have responded to your question. I was leaving it in the hope that someone with greater engineering knowledge than me would answer your question.

With injected systems it is very easy to flood. The primer pump applied for just a few seconds provides sufficient fuel for the engine to fire. When the engine is turned over to start it will also draw in further fuel if the mixture is not in the off position and therefore flood the engine. You will know that once the engine fires and runs it is important to immediately move the mixture to rich to provide fuel for the engine to continue to run.

Big Pistons Forever 25th Nov 2021 02:47

Under almost all conditions the prop will be windmilling so the check is to basically set the engine up to start firing by making sure it is getting fuel. There is a note that if the prop is stopped to lean the mixture to achieve a start if the engine does not start when the starter is activated


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