A strange richness...

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.

Yesterday, after a short stop for a piece of pie ala mode at a nearby
airport, I primed a few pumps, cracked the throttle, and started
cranking with the mixture at full lean. I slowly enrichened the
mixture until the engine caught...at which point it ran VERY rough, and
did not want to stay running.

This condition continued until I LEANED the mixture back, at which
point everything returned to normal. I was able to slowly enrichen
back to full rich, with no further difficulty. Mag checks were normal,
and the flight home -- after a very careful and prolonged run up -- was
normal.

What happened here? Why did this technique induce an over-rich
condition? Theories, anyone?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay,

I also fly a C Model Aztec and use the same technique
to start the engines. In my experience, the engine needs
no priming via boost pump when hot, and you need to let
the engine fire and run for a couple of seconds before
begining to open the mixture, or you end up flooding the engine.

I used to wonder if the engines needed priming or were flooded
when hot. I've learned through experience that in my case, they
are always on the verge of being flooded when hot.

Ronnie

"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

(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.

Yesterday, after a short stop for a piece of pie ala mode at a nearby
airport, I primed a few pumps, cracked the throttle, and started
cranking with the mixture at full lean. I slowly enrichened the
mixture until the engine caught...at which point it ran VERY rough, and
did not want to stay running.

This condition continued until I LEANED the mixture back, at which
point everything returned to normal. I was able to slowly enrichen
back to full rich, with no further difficulty. Mag checks were normal,
and the flight home -- after a very careful and prolonged run up -- was
normal.

What happened here? Why did this technique induce an over-rich
condition? Theories, anyone?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay,

I also fly a C Model Aztec and use the same technique
to start the engines. In my experience, the engine needs
no priming via boost pump when hot, and you need to let
the engine fire and run for a couple of seconds before
begining to open the mixture, or you end up flooding the engine.

I used to wonder if the engines needed priming or were flooded
when hot. I've learned through experience that in my case, they
are always on the verge of being flooded when hot.

Ronnie

"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

(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.

Yesterday, after a short stop for a piece of pie ala mode at a nearby
airport, I primed a few pumps, cracked the throttle, and started
cranking with the mixture at full lean. I slowly enrichened the
mixture until the engine caught...at which point it ran VERY rough, and
did not want to stay running.

This condition continued until I LEANED the mixture back, at which
point everything returned to normal. I was able to slowly enrichen
back to full rich, with no further difficulty. Mag checks were normal,
and the flight home -- after a very careful and prolonged run up -- was
normal.

What happened here? Why did this technique induce an over-rich
condition? Theories, anyone?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay,

I also fly a C Model Aztec and use the same technique
to start the engines. In my experience, the engine will
be flooded if you run the boost pumps when hot; When
not, it needs no priming. In addition, you need to let
the engine fire and run for a couple of seconds before
begining to open the mixture, or you end up with the
engine flooded even with no prime.

I used to wonder if the engines needed priming or were flooded
when hot. I've learned through experience that in my case, they
are always on the verge of being flooded when hot.

Is your Pathfinder fuel injected?

Ronnie

"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

(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.

Yesterday, after a short stop for a piece of pie ala mode at a nearby
airport, I primed a few pumps, cracked the throttle, and started
cranking with the mixture at full lean. I slowly enrichened the
mixture until the engine caught...at which point it ran VERY rough, and
did not want to stay running.

This condition continued until I LEANED the mixture back, at which
point everything returned to normal. I was able to slowly enrichen
back to full rich, with no further difficulty. Mag checks were normal,
and the flight home -- after a very careful and prolonged run up -- was
normal.

What happened here? Why did this technique induce an over-rich
condition? Theories, anyone?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

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? Always follow the POH or manufactures recommendations for your
aircraft or configuration, the Aztruck may not have the same throttle body
or injectors that you have.

On our Pawnee O-540, 250HP, no "injection", on a warm engine, one throttle
pump with the mixture full rich and back up to 1/2 throttle, left mag on and
hit the starter, starts in two blades reduce power and bring the right mag
online. I always shut down with mixture to idle cut off. Others tend to
prefer to run at idle and kill the mags for engine shut down, then they
touch nothing on restart but mags and starter, and it starts right up. I've
also seen raw fuel drain from the carb on their shut down technique.

On the Seneca II, the "book procedure" (cold engine) is mixture full rich,
throttle to 1/2. Electric primers to stabilize fuel pressure (about 4
seconds), release the primer and hit the starter, very smooth start. I've
found at higher airport altitudes and within an hour of landing, engine
still hot, this can tend to over prime or flood the engine very easily. But
then it's to the "flooded engine check list".

I had one airplane that was always hard to start... so when in doubt, flood
it and then do the flooded engine start.. worked every time.. because at
least then you knew what you were dealing with.

BT

"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

(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.

Yesterday, after a short stop for a piece of pie ala mode at a nearby
airport, I primed a few pumps, cracked the throttle, and started
cranking with the mixture at full lean. I slowly enrichened the
mixture until the engine caught...at which point it ran VERY rough, and
did not want to stay running.

This condition continued until I LEANED the mixture back, at which
point everything returned to normal. I was able to slowly enrichen
back to full rich, with no further difficulty. Mag checks were normal,
and the flight home -- after a very careful and prolonged run up -- was
normal.

What happened here? Why did this technique induce an over-rich
condition? Theories, anyone?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

With my Super Viking, Continental IO520-D, I used a similar method to
Jim's... Was able to hot start within 3 blades 99% of the time... And
likewise, you couldn't slam the mixture to full rich or it would flood,
you advanced it gently feeling the engine getting smoother or rougher
as you went and reacting appropriately... Also flew a D model Aztec
heavily during those years.. Same method, same results... Once you
know your engines you can almost 'feel' how much or how little to
prime... Flooding the engine and then pumping down is the most likely
way to run down the battery, melt the solder in the starter, and leave
the pilot in a swearing heap, so of course it is the recommended method
in the POH...

denny

: On our Pawnee O-540, 250HP, no "injection", on a warm engine, one throttle
: pump with the mixture full rich and back up to 1/2 throttle, left mag on and
: hit the starter, starts in two blades reduce power and bring the right mag
: online. I always shut down with mixture to idle cut off. Others tend to
: prefer to run at idle and kill the mags for engine shut down, then they
: touch nothing on restart but mags and starter, and it starts right up. I've
: also seen raw fuel drain from the carb on their shut down technique.

In general, it's a bad idea to use the throttle pump to "prime" an engine.
The accelerator pump squirts a surprisingly robust stream of raw fuel straight up
(assuming carb-on-bottom-of-oil-pan arrangement). Unless the engine is being cranked,
that fuel will *immediately* drip straight back down to the carb, do no good for
priming, and create a fire hazzard under the cowling. On a quick-turn with a hot
engine (O-360 in my case), I'll do the throttle-pump (once or twice), but ONLY while
cranking the engine. The squirt of the accel pump presumably will hit the bottom of
the oil pan, partially atomize, and get sucked into the cylinders. Even that is not
as fast/reliable as the primer, which injects directly at the intake valve on all
cylinders.

...just food for thought. Whatever floats your 'scope.

-Cory


************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

"BTIZ" wrote in message
news:1ti3g.8790$Qz.8436@fed1read11...
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? Always follow the POH or manufactures
recommendations for your aircraft or configuration, the Aztruck may not
have the same throttle body or injectors that you have.

Quite! Pumping the throttle on a FI engine serves absolutely NO PURPOSE.


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

Matt,
There's a little confusion in this thread.
Jay's engine is a carbureted O-540, mine are IO-540's. You are correct, no
need to "pump" the throttle of a FI engine, no accelerator pump. I also
agree with the comment made about only pumping the throttle of a carbureted
engine while cranking.
Jim

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"