REFLECTOR: IO-550N Hot Start Procedure

[Bob Jackson]

When you go on an extended cross country 'barnstorming' tour like I'm
currently on, you are forced to face little issues that you don't normally
encounter, or can primarily avoid during normal operations at home - or
maybe 'manage' by minimizing the opportunities (like in my case right now,
hot start, situations).

 

So now, while making an extended cross country through the West -- I'm
making lots of quick turn fuel stops, and it's very hot on the ramp in many
places.  

 

There are many Velocity's flying with the wonderful IO-550N engine - does
anyone have a reliable Hot Start procedure for the IO-550N -- particularly
for when it's been sitting on a hot ramp and shut down for less than, say,
an hour?  I know the main issue with the IO-550N is fuel vaporizing in the
fuel injector lines that run across the top of (a hot, non-operating during
the fuel turn) engine.  

 

We have avoided the "flood it, then start it in Idle Cutoff and wait for it
to catch before coming out of Idle Cutoff method", because washing the oil
off the cylinder walls with all that fuel doesn't seem like it could be very
good for the metal or the life of the engine (plus I don't have enough hands
to hold down the starter button, and jockey the Mixture, Throttle (and fuel
boost switch) controls all at the same time with the other hand!  

 

The best Hot Start method we have so far is:

1.	Mixture to Idle Cutoff - run Fuel Boost HIGH for about 30 seconds
(until you see fuel coming out of the overboard cylinder drain under the
engine) to re-circulate and cool the fuel in the engine driven fuel pump
2.	Mixture - Full Rich
3.	Throttle - WOT
4.	Fuel Boost - LOW (just for a second or so, presumably to 'blow' some
of the vapor out of the fuel injector lines
5.	Crank Engine
6.	Slowly (WOT to Idle in ~10 seconds) pull the Throttle back from WOT,
looking for the position with the right fuel-to-air balance until the engine
catches

 

This method generally works, but it's not 100% reliable and we still get
into conditions where we seem to either get it flooded or starved, and we
can't tell which one.  We start from WOT throttle and slowly reduce while
cranking rather than the other way around (starting from Idle and slowly
increasing toward WOT) because beginning from WOT and reducing, you are
already moving in the right direction to minimize overspeed conditions when
it does catch.

 

Can someone share a reliable IO-550N Hot Start procedure that works for
them?

 

Thanks,

Bob Jackson

N2XF

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