Fuel injection explanation

wrote in message
...
On Mon, 21 Jun 2004 13:04:33 GMT, EDR wrote:
Throttle is supposed to be advanced 1/4", but since the mixture
control is closed and the engine had stopped for lack of fuel, where
is the gas coming from to start the engine?

http://groups.google.co.uk/groups?q=...sson.se&rnum=1

or

http://makeashorterlink.com/?H50622F98

I asked this question last time...

Paul

On a hot start, I cool the pump body by running the battery operated
pump with the mixture closed in the Idle Cut Off position. This (on the
lycoming IO-360's Ive used it on) runs fresh "cool" fuel from the tanks,
through the pump body and back to the tank. I do this for a full minute,
then prime and start as a normal start.

Other options are to intentionally flood the engine (mildly so) and then
do a flooded start procedure (throttle wide open, mixture off and you
seem like you need 3 hands..)

Dave
wrote:

On Mon, 21 Jun 2004 13:04:33 GMT, EDR wrote:


Throttle controls air (air box, throttle plate), mixture controls fuel
(needle valve, spider injector controller).
Because excess fuel has been injected into the engine; enough to start
and run fro a few seconds, until the mixture lever is advanced,
allowing fuel to flow, propelled by the engine driven pump.


Thanks for the explanation EDR. My question then is: If the engine is
shut down by pulling the mixture control to idle/cutoff, where does
the engine get the fuel it needs to start again when you attempt a hot
start 15 minutes later? You aren't supposed to use the auxiliary fuel
pump and the mixture is supposed to remain at idle/cutoff during the
start in this situation.

Throttle is supposed to be advanced 1/4", but since the mixture
control is closed and the engine had stopped for lack of fuel, where
is the gas coming from to start the engine?

Thanks, Corky Scott

Steve Robertson wrote:

As to your question about where the engine gets its fuel to hot start ... Even
though you killed the engine with the mixture control, a bit of fuel will still
leak out of the injector lines and into the intake after the engine is shut
down.

Interesting. Since the reason usually advanced for using the mixture to shut down is
that the engine will be starved for fuel and consequently will not fire if the prop
is moved on the ground, it seems that fuel injection is less safe than carburetion.
At least in this regard.

George Patterson
None of us is as dumb as all of us.

In article .net,
Dave S wrote:

On a hot start, I cool the pump body by running the battery operated
pump with the mixture closed in the Idle Cut Off position. This (on the
lycoming IO-360's Ive used it on) runs fresh "cool" fuel from the tanks,
through the pump body and back to the tank. I do this for a full minute,
then prime and start as a normal start.

Which aircraft do you have the engine in?
Not all fuel systems with Lycoming IO-360's have a fuel return line (at
least it is not shown on the fuel system diagram).

All the Continentals I have seen have the fuel return to either the
left main or the selected tank.

This is why the Continental procedure calls for
- Mixture idle/cutoff
- Throttle open
- Fuel pump on for 30 seconds then off

With the fuel flowing through the spider and back to the tank, the fuel
lines are purged and cooled.
Without a fuel return line, there is no means of purging the line and
cooling it. It would only pressureize the line to the pumps ablility.

"G.R. Patterson III" wrote in message
...

Steve Robertson wrote:

As to your question about where the engine gets its fuel to hot start
.... Even
though you killed the engine with the mixture control, a bit of fuel
will still
leak out of the injector lines and into the intake after the engine is
shut
down.

Interesting. Since the reason usually advanced for using the mixture to
shut down is
that the engine will be starved for fuel and consequently will not fire if
the prop
is moved on the ground, it seems that fuel injection is less safe than
carburetion.
At least in this regard.

I asked an examiner this question...he said it was correct, but that
it only takes a few hours for all the fuel to evaporate so it's likely
to be fine after that!

Paul

Negatory, good buddy. At least not with the Bendix RSA FI controller. Fuel
isn't returned to the tanks. Some of the Continental FI schemes do that,
however.

Best regards,

Steve Robertson
N4732J 1967 Beech Musketeer Super III

Dave S wrote:

On a hot start, I cool the pump body by running the battery operated
pump with the mixture closed in the Idle Cut Off position. This (on the
lycoming IO-360's Ive used it on) runs fresh "cool" fuel from the tanks,
through the pump body and back to the tank. I do this for a full minute,
then prime and start as a normal start.

Other options are to intentionally flood the engine (mildly so) and then
do a flooded start procedure (throttle wide open, mixture off and you
seem like you need 3 hands..)

Dave
wrote:

On Mon, 21 Jun 2004 13:04:33 GMT, EDR wrote:


Throttle controls air (air box, throttle plate), mixture controls fuel
(needle valve, spider injector controller).
Because excess fuel has been injected into the engine; enough to start
and run fro a few seconds, until the mixture lever is advanced,
allowing fuel to flow, propelled by the engine driven pump.


Thanks for the explanation EDR. My question then is: If the engine is
shut down by pulling the mixture control to idle/cutoff, where does
the engine get the fuel it needs to start again when you attempt a hot
start 15 minutes later? You aren't supposed to use the auxiliary fuel
pump and the mixture is supposed to remain at idle/cutoff during the
start in this situation.

Throttle is supposed to be advanced 1/4", but since the mixture
control is closed and the engine had stopped for lack of fuel, where
is the gas coming from to start the engine?

Thanks, Corky Scott

Steve Robertson wrote in message ...
Also FWIW, I really don't like fuel injection on airplane engines. Sure it's
great not to have to worry about carb heat. But instead I worry about hot
starts and plugged injectors.

That's why God invented engine monitors. I can't imagine owning an
injected engine without an engine monitor.

-Robert, IO-360-A3B6 Mooney driver

Here is how I start up a Cessna 172-S (IO-360 180HP):

Cold start (oil temp below green arc): Master on, Trottle foward,
mixture foward, fuel pump for 3 sec (look for rise in fuel flow
indicator), throttle to 1/4 inch (about 1000 RPM), Ignition

Warm start (Oil temp in the green arc): Master on, Throttle foward,
mixture foward, fuel pump for 1 sec., mixture back to cut-off,
Ignition. When engine fires, smoothly but quickly retard the throttle
to about the 1000 RPM range, and quickly follow with mixture to full
rich.

Hot start (Oil temp in green arc and engine shut down within last 30
minutes): Master on, Throttle foward, mixture foward, mixture back to
cut-off,

Why mixture forward followed by mixture back to cutoff?




When the plane was shut down last, it was accomplished by pulling the
mixture to cutoff and starving the engine of gas. By pushing the mixture
full foward for the hot start, The fuel in the lines primes the engine
without the need for additional priming with the aux. fuel pump. The engine
catches almost as soon as you engage the starter with a hot start.

Steve Robertson wrote:
As to your question about where the engine gets its fuel to hot start ...
Even
though you killed the engine with the mixture control, a bit of fuel will
still
leak out of the injector lines and into the intake after the engine is shut
down.

In article , G.R. Patterson III
wrote:
Interesting. Since the reason usually advanced for using the mixture to shut
down is
that the engine will be starved for fuel and consequently will not fire if
the prop
is moved on the ground, it seems that fuel injection is less safe than
carburetion.
At least in this regard.

A better answer might be that retarding the mixture creates too lean a
mixture for ignition.
For example, if the engine does not quit with the mixture retarded
(chugs, diesels), you can then advance the throttle and create a leaner
mixture.