A strange richness...

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.

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

I've got an IO-360 and I have always used the crank at lean procedure. In
fact, I crank at full lean until it fires. I don't open the mixture until I
get some sort of bark from the engine.

When hot, no priming. Works every time. I fly an amphib so being able to
reliably start - even when hot - is very important to me since I could be
drifting toward obstacles after pushing off from a dock.

I tend to underprime. I would rather prime a little, try to start, prime a
little more, start. I find this more reliable than overpriming and then
trying to clear the engine.

The only time I have not been able to start is when I primed a hot engine.

--
-------------------------------
Travis
Lake N3094P
PWK


"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"

I also have an AEIO-540 in my Extra, and the starting procedure is:

Mixture full rich
Throttle full forward
Run electric boost pump for a few seconds
Idle cut off
Throttle cracked
Crank
Mixture forward

Starts every time, hot or cold, and this is with a lightweight starter and
pretty small battery.

Sounds pretty similar.

O-320 in a 172M

When cold using closed throttle - Minimum prime (maybe 1), check
compression of all 4 cyls, roll the airplane out, then 1/2 shot on
initiation of cranking.

When warm - cracked throttle, no prime. It will be appear slightly
flooded.

Burning autofuel, I also shut off the fuel & run the carb bowl dry if
it won't be flown for a week or more. Fresh fuel in the bowl & primer
really helps.

Burning autofuel, I also shut off the fuel & run the carb bowl dry if
it won't be flown for a week or more. Fresh fuel in the bowl & primer
really helps.

I've run over 6500 gallons of mogas through Atlas, and he (the plane,
that is) was run on exclusively mogas by previous owner(s) for almost
10 years.

I've never heard of what you're talking about before. Are you saying
that mogas starts to go bad after a WEEK?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

I've never heard of what you're talking about before. Are you saying
that mogas starts to go bad after a WEEK?

Summer gas v winter gas? (different vapor pressures)

http://www.epa.gov/otaq/volatility.htm

Remember that autogas does not have the stabilizers that avgas has.

http://www.chevron.com/products/prod...ationfuel/8_ag
_perf.shtm

http://www.chevron.com/products/prod...ationfuel/11_a
g_refining.shtm

www.eaa.org/education/fuel/autogas_vs_avgas.pdf

http://www.avweb.com/news/maint/187232-1.html

http://www.generalaviationnews.com/e...lasso?-token.k
ey=8901&-token.src=column&-nothing

Jay Honeck wrote:

I've never heard of what you're talking about before. Are you saying
that mogas starts to go bad after a WEEK?

If I don't purge the float bowl, starting cold w mogas is less
predictable, and a bigger slug of fuel will puddle and remain in the
intake manifold after startup. This slug goes thru the engine with a
lot of burping & coughing etc as the throttle is first advanced after
starting. I consider this tacky. I don't like flying behind engines
or with pilots that don't start well - just on general principle.

This doesn't happen if the engine is warm as the oil heats the manifold
which minimizes fuel condensation.

Mogas has a wider distillation temp range than a/c fuel. The light
components of mogas will more easily evaporate from the bowl leaving
you with a more-like-kerosene mixture for starting, depending on how
long it has been sitting. Yes you can usually get things going, but it
does mean grinding the starter more.

In the fifties farmers would burn something we called "Powerfuel" in
their carburated tractors. I worked in a garage & we could never get
them going without priming with fresh gasoline.

My lawn mowers like this too. Especially my snow blower. Can aircraft
be far behind?

On 26 Apr 2006 20:48:16 -0700, "nrp" wrote:

Jay Honeck wrote:

I've never heard of what you're talking about before. Are you saying
that mogas starts to go bad after a WEEK?

If I don't purge the float bowl, starting cold w mogas is less
predictable, and a bigger slug of fuel will puddle and remain in the
intake manifold after startup. This slug goes thru the engine with a
lot of burping & coughing etc as the throttle is first advanced after
starting. I consider this tacky. I don't like flying behind engines
or with pilots that don't start well - just on general principle.

This doesn't happen if the engine is warm as the oil heats the manifold
which minimizes fuel condensation.

Mogas has a wider distillation temp range than a/c fuel. The light
components of mogas will more easily evaporate from the bowl leaving
you with a more-like-kerosene mixture for starting, depending on how
long it has been sitting. Yes you can usually get things going, but it
does mean grinding the starter more.

In the fifties farmers would burn something we called "Powerfuel" in
their carburated tractors. I worked in a garage & we could never get
them going without priming with fresh gasoline.

My lawn mowers like this too. Especially my snow blower. Can aircraft
be far behind?

Thanks that makes a lot of sense. I've aways found my engine 0-290D to
be harder to start with autoffuel than 100LL even though it runs much
better on it. I amost always have my engine stall after about 20
seconds during a cold start regardless of priming or throttle pumping.

: In the fifties farmers would burn something we called "Powerfuel" in
: their carburated tractors. I worked in a garage & we could never get
: them going without priming with fresh gasoline.

My dad's 1939-ish Oliver-60 Row Crop (that he still uses to plow snow and run
the PTO pump for the logsplitter) was one such creature. It would run on either gasoline
or kerosene ("farm-fuel" is what I'd heard it called). That tractor's a hoot to drive
around.

-Cory

--

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