Shutting down engine Question

John Galban wrote:

Don Tuite wrote in message
. ..

On hot days, the O-300 in the 'Hawk tends to diesel on after you pull
the mixture. Opening the throttle a little makes it stop.

Don,

Sounds like you have a fuel leak into the manifold. Pulling the
mixture to cutoff should, well, cut off the fuel flow. This could be
something in your carb, or might be a leak in your primer system.
Either way, it shouldn't continue to run after you've cut off the fuel
supply. That's an indication of a problem in the fuel system.

John Galban=====N4BQ (PA28-180)

Concur. Our O-300 has never dieseled.

We do have a problem with fouled bottom plugs though. I never thought it was
related to shutdown procedure until this thread, but now I will consider
it. Always thought it was too much priming.


--
Frank....H

"Dennis O'Connor" wrote in message ...
Lotsa "depends"... One of the benefits of owning a plane, or flying the
same one most of the time, is that you get to know the idiosyncrasies... On
mine, from experience I know the proper rpm for mixture cutoff that gives
the smoothest shutdown, and 99 times out of a 100 results in both props
stopping at the same angle... Just a game I play for my own satisfaction...
There is also the method of going to 1800-2000 rpm, pulling the mixture as
lean as it will go without shutting down, wait 10-15 seconds, then gently
close the throttle to idle, wait until the engine slows, then fully cut the
mixture... This helps to clear lead fouling off the plugs...
denny

We run an O-360 with an Ellison TBI... the plugs tend to foul very
quickly, even if the engine is leaned during taxi. Therefore, our
shutdown procedure is to run up to about 1300 rpm and pull the mixture
out to right about peak. We let it run like that for 20-30 seconds,
then throttle back to about 800. Mixture is chopped to cutoff, then
we push the throttle up. As soon as it starts to speed up, we cut the
ignition off.

This process results in a clean start for next time, and the least
amount of shaking we've managed to accomplish without the engine
deciding to spin backwards for a few revs.

Lisa wrote in message ...
Perhaps this doesn't matter much for a non-turbocharged engine,
but an instructor says that it is best to idle the engine at
1,000 RPM for a few moments before Mixtu Idle Cut-Off at that
RPM to shut down.

The POH says throttle full aft, then mixture cut-off to shut
down.

Which is best?

The idle at 1,000 RPM sure helps in my IO-360 engine. My engine hot
starts great, and cold starts great, but is very hard to warm start.
Idling at 1,000 RPM (or 1,200 RPM) for a couple minutes seems to make
a huge difference.

-Robert

"Dan Luke" wrote in message ...
"Roger Long" wrote:
1800 is better (with the leaning mentioned above) but you won't
make any friends in the tiedowns using those RPMs.

Yes. The procedure must be used with consideration for others.

Since I started following Lycoming's procedure, I no longer have any
fouling problems.

What made a HUGE difference for me was just leaning in taxi. If you
increase throttle and the RPM increases during taxi you have the
mixture set too rich. Before I realized this I had to have my IO-360's
plugs cleans twice in 6 months. Now I don't think about it until
annual.

-Robert

Nathan Young wrote in message . ..

Does the Lycoming service letter explain what running at 1800RPM
accomplishes?

I'd be willing to guess that the purpose is to increase combustion
temperatures and burn off any lead deposits. At 1000 rpm my EGT will
barely move off the peg with max leaning. At 1800, it's good and hot.

John Galban=====N4BQ (PA28-180)

"Robert M. Gary" wrote:
What made a HUGE difference for me was just leaning in taxi.

Ditto.

If you increase throttle and the RPM increases during taxi you
have the mixture set too rich.

Amen. (Two mechanics have told me I will "burn the valves" by doing
this!)

Before I realized this I had to have my IO-360's plugs cleans
twice in 6 months. Now I don't think about it until annual.

Yep.
--
Dan
C172RG at BFM
(remove pants to reply by email)

When we used to run Cessna 150s, we often found them hard to start.
Then we noticed that just after a flight, or lengthy runup before
inspection, that oil would dribble out of the bottom plug holes when
we pulled the plugs. These engines tend to foul the bottom plugs at
idle for some reason, and we instituted a 1700 RPM runup prior to
shutdown to clear them. No more hard starts or fouled plugs.
We have few fouling problems with the Lycs, other than with too
much circuit work.

Dan