The 3003rd lycoming hot start thread

[ArtVandelay]

You will not flood the engine if the mixture is at ICO.  In fact, some Times you should have the pump running during start, because th engine starts then will die immediately after due to vapor locked fuel lines. A running fuel pump prevents this..
 

That's what I heard for Continentals, their fuel is recirculated, not Lycomings.
Some fuel gets in, that is why we can start with mixture ICO.

[Cyril Gibb]

In reading between the lines of various methods for fuel injected engines in both this thread and the cold start thread, I think I'm hearing differences in the status of the fuel system when a start is attempted.

My electric pump was taking 10-12 seconds with ICO to get to the green.  There also was a slight seepage so off to the rebuilder it went.  The temporary spare took about 5 seconds or so and now the newly rebuilt one also about 5 seconds to green.  I thought that was normal, but I'm hearing that some of you can get fuel pressure into the green after just a second of boost.  What should it be?  Have all my pumps been flawed, or are some pumps producing excess pressure/volume?

Next observation.  When I shut down with ICO, my fuel pressure stays up for at least several hours.  Again, it sounds like some use boost before starting to get the gauge into the green. How long should the fuel pressure be maintained at ICO?  Where does the pressurized fuel go? Back through the pumps?

What is "normal"?

[jetdriven]

18 hours ago, Mooney_Mike said:

That hasn't been my experience. I don't use the fuel pump on hot engine starts.

Some airplanes do. Soon after starting, the fuel pressure goes below 13 PSI and the engine dies again. It vapor lock on the pump inlet side. Running the electric pump keeps the mechanical pump supplied with fuel.  

[jetdriven]

18 hours ago, teejayevans said:

That's what I heard for Continentals, their fuel is recirculated, not Lycomings.
Some fuel gets in, that is why we can start with mixture ICO.

The reason you can start the engine with the mixture at ICO is becuase the fuel in the fuel divider and injection lines boils and forces  some liquid through the injectors and into the cylinders.  Like a built in primer, but there is vapor between the fuel servo and the injectors. But the airplane wouldn't hold fuel pressure for an hour or more if it was leaking.  Moving the mixture off ICO dumps the fuel pressure to zero immediately.  

Edited February 23, 2017 by jetdriven