A strange richness...

My guess, and it's just a guess, is that you flooded the primed cylinders
while the remaining cylinders fired and operated normally, thus the
roughness.

As you advanced the mixture, the primed cylinders continued to be flooded
but the non-primed cylinders operated normally, albeit at a possibly rich
mixture.

As you retarded the mixture, the primed cylinders were then able to
completely burn the leaner mixture and clean themselves up.

Jim

"Jay Honeck" wrote in message
oups.com...
You "primed a few pumps", I take it this means throttle pumping
(accelerator
pumps?) on an already hot engine? I'd guess you did over prime and then
flood the engine.. I am not sure of your engine but I presume it is also
an
IO-540?

Nope. Pumped the primer a couple of times. (The little
Coleman-lantern-style-thingie)

The engine is a normally-aspirated O-540.

I obviously flooded it, but I don't quite understand how this can be
so, simply by starting with the mixture at idle/cut-off, rather than at
full rich.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

My guess, and it's just a guess, is that you flooded the primed cylinders
while the remaining cylinders fired and operated normally, thus the
roughness.
As you advanced the mixture, the primed cylinders continued to be flooded
but the non-primed cylinders operated normally, albeit at a possibly rich
mixture.
As you retarded the mixture, the primed cylinders were then able to
completely burn the leaner mixture and clean themselves up.

This makes as much sense as anything -- thanks.

I probably shouldn't have used the primer at all, but it was in that
goofy, "in-between" length of time, where the engine wasn't really
still "hot" -- but it wasn't really "cold" either.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On 2006-04-26, Jay Honeck wrote:
I probably shouldn't have used the primer at all, but it was in that
goofy, "in-between" length of time, where the engine wasn't really
still "hot" -- but it wasn't really "cold" either.

I've found on all the carburetted engines I've flown behind - priming is
only needed if the engine is absolutely stone cold. Even if the plane
has been just sitting in the sun and not flown in 3 days, the warmth of
the sun is enough that priming isn't usually needed.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

Jay Honeck wrote:
Nope. Pumped the primer a couple of times. (The little
Coleman-lantern-style-thingie)

I never use the primer when the engine is even just warm.
In fact, the O-540 on my Comanche cranks right up with no
priming even after several days of sitting. I usually only
need to prime on cold days, which isn't many in southern Georgia.

If it hasn't flown for a couple of weeks and won't fire up
after a few cranks then I might pump it once or twice.

we only use the manual primer on cold days.. less than 40F and never on a
warm engine

I may have mistyped earlier when I referenced IO- vs O-, yes there is no
throttle pump on the IO-
BT


"ktbr" wrote in message
...
Jay Honeck wrote:
Nope. Pumped the primer a couple of times. (The little
Coleman-lantern-style-thingie)

I never use the primer when the engine is even just warm.
In fact, the O-540 on my Comanche cranks right up with no
priming even after several days of sitting. I usually only
need to prime on cold days, which isn't many in southern Georgia.

If it hasn't flown for a couple of weeks and won't fire up
after a few cranks then I might pump it once or twice.

Are Aztec engines Continentals or Lycomings?
Continentals sometimes have a fuel return line.
I do not know if Lycomings do, also, but I have not seen one that does
on any of the aircraft I have flown.

Lycoming IO-540C4B5 on the non-turbo models.

"john smith" wrote in message
...
Are Aztec engines Continentals or Lycomings?
Continentals sometimes have a fuel return line.
I do not know if Lycomings do, also, but I have not seen one that does
on any of the aircraft I have flown.

I agree with Ronnie and Denny, hot starts in the Aztec do not require any
priming.

I showed this method to one of our partners the other day and he was happily
surprised at how easy it started. It's simply a matter of obtaining the
correct mixture for combustion, hot/thin air requires very little fuel, add
fuel and the mixture is too rich. The "fuel pump on, then off, full open
throttle, full lean mixture, crank until your battery, starter, patience are
all worn out" POH method simply sucks. It also recommends starting the left
engine first (carry over from when only the left had a generator) but we
usually start the right first, it's closer to the battery, then we've got an
alternator to help the battery send adequate amps through the 20 some feet
of aluminum cable over to the left engine. The POH is usually the "bible"
but when the airplane changes and the POH doesn't, it can really muck you
up.

I typically can tell when the engines are about to fire, then I begin
advancing the mixture, but not too fast or it will kill the engine. It's a
matter of feeding the engine just enough fuel so the engine driven fuel pump
can keep it running.

The flight school that I used to work with had an Archer that students
routinely had trouble starting, they flooded it continually. They'd come
back into the office saying that "they did the hot start method, then
flooded method, now it barely cranks." I'd show them that when hot, it
started best with the mixture pulled back about 1/2 way, not as the POH
advised.

One thing that aggressive ground leaning can teach is just how lean a hot
engine will run. After a flight, while you're taxiing in, lean the engine
so it will barely run, then enrichen slightly. Make a note of where the
mixture lever is. The engine should start when hot at this same mixture
setting without flooding.

YMMV but once you learn the engine it won't vary very much.

Jim

Jay Honeck wrote:
On our flight to Nevada, I was impressed with the smoothness and
car-like predictability of Jim Burns' start-up technique with his
Lycoming IO-540s. Jim had a way to start them that I'd not seen
demonstrated before, which I will describe he

1. Fuel pump on
2. Electric primer on for (a few?) seconds
3. Crack throttle
4. With mixture at full lean, start cranking
5. Gradually enrichen the mixture until the engine fires

(I may have some of this wrong, as the Aztec has nearly every switch
and gauge in bizarre, usually invisible locations...)

By using this method, his engines both started without cranking or
coughing, just like my Subaru.

So, of course, I've been experimenting with this method, which is quite
different than the one described in my POH. (Which basically says
"crank at full-rich"...) It has worked perfectly several times,
especially on hot starts, until yesterday.

.... but your engine is carbureted, is it not?
.... and Jims' are fuel-injected?
.... and Jim's POH specifies this starting procedure?
.... and your POH specifies a different procedure?

I question the wisdom of copying someone else's starting procedure just because
it works well on their engine.

If you have the same engine, well, nevermind.

Dave

"Jay Honeck" wrote in message
oups.com...
On our flight to Nevada, I was impressed with the smoothness and
car-like predictability of Jim Burns' start-up technique with his
Lycoming IO-540s. Jim had a way to start them that I'd not seen
demonstrated before, which I will describe he

1. Fuel pump on
2. Electric primer on for (a few?) seconds
3. Crack throttle
4. With mixture at full lean, start cranking
5. Gradually enrichen the mixture until the engine fires

Works on the TCM IO-550 including the TN version.

BTW, If the mixture is already full rich, how do you enrich it further?

--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO