Ok, so how *do* you hotstart your IO-540?

Paul Tomblin wrote:
In a previous article, said:
On 2007-07-16, Paul Tomblin wrote:
I know that hot starting IO-540s is a subject for considerable debate. I
was taught a method that I was told worked 100% of the time[1], and up
until yesterday it had. But yesterday, after flying for an hour and then
sitting in the hot sun for half an hour waiting for customs, I couldn't
restart the Lance and had to have it towed back to the tie down area.
I think it's the same as computers with lots of SCSI hardware - you have
to make sure you've sacrificed enough chickens recently. Or AN hardware.
I forget which.

Don't be silly. For SCSI hardware, it's black goats. At midnight. With
a silver dagger. And there are perfectly valid technical reasons why.

Is it because the must be properly terminated?

On 2007-07-17, Paul Tomblin wrote:
Don't be silly. For SCSI hardware, it's black goats. At midnight. With
a silver dagger. And there are perfectly valid technical reasons why.

Ah! Now I know why I had so much trouble with that bloody server
yesterday. I've been sacrificing the wrong things all along.

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

On Jul 16, 2:04 pm, (Paul Tomblin) wrote:
I know that hot starting IO-540s is a subject for considerable debate. I
was taught a method that I was told worked 100% of the time[1], and up
until yesterday it had. But yesterday, after flying for an hour and then
sitting in the hot sun for half an hour waiting for customs, I couldn't
restart the Lance and had to have it towed back to the tie down area.

So what would you do in that situation?

I would use the last-resort starting procedure for injected engines.
It was taught to me years ago by an ATP/A&P/CFI owner of multiple
aircraft, and it has NEVER failed to work in my experience, on any
horizontally opposed injected engine that I have ever dealt with,
large or small, four cylinders or six, high compression or low,
Lycoming or Continental. Now I pass it on to you.

Mixture full rich
Full throttle
Run fuel pump a few seconds (if you have a fuel pressure/flow gauge,
run fuel pump until it stops coming up)
Fuel pump off
Mixture idle cutoff
Crank
When it catches (and it will), simultaneously enrich the mixture and
pull back the throttle.

Here's why it works:
With throttle and mixture full forward, the fuel pump forces cold fuel
through all the lines, cools the lines, eliminates the vapor lock -
and floods the engine.
With fuel pump off and mixture at idle cutoff, no fuel gets to the
cylinders.
With the throttle full open, lots of air gets to the cylinders.
With a few revolutions, the flooding is eliminated - the air-fuel mix
going into the cylinders starts out way too rich (flooded) but quickly
leans out enough for combustion.
Now the engine is running - all you need to do is keep it from dying,
by enriching the mixture.

It's not terribly important to pull back the throttle quickly, either
- just stand on the brakes. So if you can't do both (enrich mixture
and close throttle) at once, push the mixture rich and then pull back
the throttle.

It's not wonderful for the engine, but it's not terrible either. It's
not like you would ever cold-start it that way. It just ran recently,
there is plenty of oil everywhere and the engine is hot. And once you
get good at it, you will be able to complete the start procedure
without the engine ever going over 2000 RPM.

If you have a procedure that consistently works, stick with it - but
when it won't work - and most every injected engine I've ever seen
eventually refuses to start - this is the method of last resort.
Never seen it fail.

Michael

On Jul 16, 10:06 pm, "Dan Luke" wrote:
"Paul Tomblin" wrote:

How long do you leave the pump on?



Until it's started. Because the mixture is still at cut-off, no fuel is
flowing.

??

Then why leave it on?

--
Dan
T-182T at BFM

Hi, I'm a student A&P (Commercial, instrument pilot) and recently
learned that the fuel vapor in the line needs to be purged to assist
starting fuel-injected engines, meaning the line between the tank and
the "spider" fuel distributor. This is why the mixture is left closed,
to clean out the line of the hot fuel vapor that will make starting
difficult.
The Lycoming manual for the fuel injectors we were working with have a
humorous, yet informative and accurate description and remedy for the
problem of hot starting fuel-injected engines.
Now I know why the old Arrow I did my commercial training in was so
hard to start after shutting down in the hot Texas Summer.

Ricky (WOW, I'm already teaching something I learned last semester!)

On Jul 16, 10:06 pm, "Dan Luke" wrote:
"Paul Tomblin" wrote:

How long do you leave the pump on?



Until it's started. Because the mixture is still at cut-off, no fuel is
flowing.

??

Then why leave it on?

--
Dan
T-182T at BFM

Oops, I think I meant fuel flows from the tank to the pump & back via
the return line which purges the line of the hot vapor.
Well, I made an A in the class, anyway.

Ricky

This works every time for me also.


Mixture full rich
Full throttle
Run fuel pump a few seconds (if you have a fuel pressure/flow gauge,
run fuel pump until it stops coming up)
Fuel pump off
Mixture idle cutoff
Crank
When it catches (and it will), simultaneously enrich the mixture and
pull back the throttle.

Here's why it works:
With throttle and mixture full forward, the fuel pump forces cold fuel
through all the lines, cools the lines, eliminates the vapor lock -
and floods the engine.
With fuel pump off and mixture at idle cutoff, no fuel gets to the
cylinders.
With the throttle full open, lots of air gets to the cylinders.
With a few revolutions, the flooding is eliminated - the air-fuel mix
going into the cylinders starts out way too rich (flooded) but quickly
leans out enough for combustion.
Now the engine is running - all you need to do is keep it from dying,
by enriching the mixture.

It's not terribly important to pull back the throttle quickly, either
- just stand on the brakes. So if you can't do both (enrich mixture
and close throttle) at once, push the mixture rich and then pull back
the throttle.

It's not wonderful for the engine, but it's not terrible either. It's
not like you would ever cold-start it that way. It just ran recently,
there is plenty of oil everywhere and the engine is hot. And once you
get good at it, you will be able to complete the start procedure
without the engine ever going over 2000 RPM.

If you have a procedure that consistently works, stick with it - but
when it won't work - and most every injected engine I've ever seen
eventually refuses to start - this is the method of last resort.
Never seen it fail.

Michael

On Jul 16, 3:04 pm, (Paul Tomblin) wrote:

I know that hot starting IO-540s is a subject for considerable debate. I
was taught a method that I was told worked 100% of the time[1], and up
until yesterday it had. But yesterday, after flying for an hour and then
sitting in the hot sun for half an hour waiting for customs, I couldn't
restart the Lance and had to have it towed back to the tie down area.

So what would you do in that situation?

On Jul 16, 3:04 pm, (Paul Tomblin) wrote:

I know that hot starting IO-540s is a subject for considerable debate. I
was taught a method that I was told worked 100% of the time[1], and up
until yesterday it had. But yesterday, after flying for an hour and then
sitting in the hot sun for half an hour waiting for customs, I couldn't
restart the Lance and had to have it towed back to the tie down area.

So what would you do in that situation?

This is straight out of the Continental Continuous Flow Fuel Injection
Manual;

"It's a hot Summer day and the pilot has just shut down the engines
after a routine flight. As you can inagine, things are pretty warm
under that engine cowling.
Well, there's something you should know about that heat. All of the
raw, liquid fuel in practically every line forward of the firewall has
turned to vapor - which would be just fine because that's the way we
want it when it enters the cylinders.
Only there's one little hitch. The injection pump cannot supply fuel
in it's vapor state fast enough at engine cranking speed to provide
adequate fuel for starting.
During the course of events that follows, the situation usually goes
from one extreme to the other and the engine becomes flooded. Well -
there's the problem - now for the solution.
Remember that electric fuel pump we mentioned earlier? Good! Because
we are going to show you how to use it to prevent this situation from
ever happening again, and in three simple steps that can be applied to
any airplane equipped with fuel injection engines.

First, place the mixture in idle cut-off or full lean position. This
prevents any quantity of fuel from reaching the cylinder and causes
all of the fuel delivered by the electric pump to return back to the
tank by way of the return line system.

Second, place the throttle in the full open position. It really
wouldn't matter about the throttle except that some aircraft makers
put safety switches on their throttles to prevent the electric pump
from operating in the high range when the throttle is retarded, so to
avoid confusion or having two sets of steps, we will use the full open
position for all airplanes.

Third, switch the electric fuel pump to it's high position. Now sit
back and relax for about 15 to 20 seconds.

While you are relaxing, here is what is happening. The electric pump
is delivering liquid fuel from the supply tank to the injection pump,
through the pump bypass valve, into the metering unit where the closed
mixture control switches fuel and vapors into the return system and on
it's way back to the tank where it came from originally.
Now the lines are free of vapor and full of liquid fuel again. In the
process of purging we have also cooled down the interior of the fuel
lines and fuel pump, therefore, vapor will not form the minute we
switch off the electric fuel pump.

Now we are ready to start the engine so first, switch off the electric
fuel pump. Now retard the throttle to the normal start position.
Advance the ixture control to full rich, mags on, and engage the
starter. The engine will start immediately because all lines and
components are full of liquid fuel and able to function as they
should. This very simple procedure will work every time and on any
engine equipped with fuel injection. Once the engine has started, the
injection pump will continue the purging operation since it does this
anyway whenever it is running. In addition, ram air from the propeller
passing into the nacelle will begin cooling the fuel lines and system
down from the outside. (A good aid to this is to open cowl flaps and/
or point into the wind)." - From Continental Continuous Flow Fuel
Injection System maintenance, overhaul, and troubleshooting manual.

Another source of hard starting difficulties with a hot engine is low
unmetered fuel pressure. With this condition you will also have rough
idling and engine stoppage during rollout after landing, followed by
difficulty in re-starting.
The solution is simple and involves checking for proper setting of
idle speed on the fuel control unit, adjusting the low unmetered fuel
pressure to specified limits, and also adjusting the idle mixture
after setting the low unmetered fuel pressure. This is an A&P job and
I won't go into details unless someone asks, my fingers are tired
after this long response!

I will add to the hot start procedure that it may be helpful to
advance mixture for a second or less until flow is just noticed. This
will clear out some or all fuel vapor between the fuel control unit
and the cylinders but you can easily flood the cylinders doing this.
Besides that, the distance between the fuel control unit and the
cylinders is small and the remaining fuel vapor will quickly be pushed
out by the advancing liquid fuel.

Ricky (student A&P)

In a previous article, Ricky said:
Another source of hard starting difficulties with a hot engine is low
unmetered fuel pressure. With this condition you will also have rough
idling and engine stoppage during rollout after landing, followed by
difficulty in re-starting.

Come to think of it, a few months ago during my BFR in this same plane,
the engine died while rolling out after the landing, and we couldn't
restart it until it cooled down. I think I might have to bring this up
with our A&P.


--
Paul Tomblin http://blog.xcski.com/
If you're not part of the solution, you're part of the precipitate.

On Jul 20, 8:50 am, (Paul Tomblin) wrote:
In a previous article, Ricky said:

Another source of hard starting difficulties with a hot engine is low
unmetered fuel pressure. With this condition you will also have rough
idling and engine stoppage during rollout after landing, followed by
difficulty in re-starting.

Come to think of it, a few months ago during my BFR in this same plane,
the engine died while rolling out after the landing, and we couldn't
restart it until it cooled down. I think I might have to bring this up
with our A&P.

--
Paul Tomblin http://blog.xcski.com/
If you're not part of the solution, you're part of the precipitate.

And since you mentioned that the method you have used for hot starts,
which previously was successful, has stopped working, then your low
unmetered fuel pressure very likely may be the culprit.

Ricky

Paul Tomblin wrote:
But yesterday, after flying for an hour and then sitting in the hot
sun for half an hour waiting for customs, I couldn't restart the
Lance and had to have it towed back to the tie down area.

For any fuel injection system that has been competently designed in the
last 40 years, the proper hot starting procedure is:

1) Leave throttle at idle
2) Crank until it catches
3) Advance throttle to desired setting

The proper cold starting procedure is:

1) Leave throttle at idle
2) Crank until it catches
3) Advance throttle to desired setting

The proper warm starting procedure is:

1) Leave throttle at idle
2) Crank until it catches
3) Advance throttle to desired setting

(There is no manual mixture control nor manual control of the fuel
pump.)

Of course, we're talking about airplanes, so none of the above applies.

Matt Roberds