"Corky Scott" > wrote in message
...
> With my last experience, the engine actually went into hydraulic lock
> without me touching the controls or using the auxiliary fuel pump.
> The prop barely turn half a turn before it stopped and the starter
> couldn't crank it anymore.

I'm not sure what exactly is going on here, but I don't think it's
"hydraulic lock". As a previous post hinted at, "hydraulic lock" is
something that is specific to only certain kinds of engines (like radials)
and not those found in C172's. It happens when oil drains into the
cylinder, putting an incompressible substance into a space that wants to
compress when the engine turns.

If you are having trouble with the starter not being able to turn the engine
on a C172, you've either got a dead battery, or something worse is going on.

When you first wrote "hydraulic lock", I actually assumed you meant "vapor
lock", which is what happens when the fuel in the fuel lines is heated to
the point of vaporization, preventing it from being pumped to the engine.
This is the usual problem when starting hot engines, especially fuel
injected ones (carbureted engines usually have enough fuel in the float bowl
to let things get sorted out during engine start, so even a little vapor in
the fuel lines won't cause a problem with starting).

But now it sounds like you did actually mean something other than "vapor
lock". I'm not sure what it was, but I'm pretty certain that, given that
you're talking about a C172, it wasn't "hydraulic lock". Even if hydraulic
lock were possible on a C172, it wouldn't be related to a hot engine start.

> There are actually two fuel pumps, one works with the engine turning,
> the other is the electric auxiliary pump. So fuel will be pumped to
> the injectors the moment the engine starts turning.

I'm not familiar with the new fuel-injected C172's, but it's entirely
possible that with the electric fuel pump running, fuel will be pumped to
the injectors and even into the engine the moment the fuel pump is turned
on, regardless of whether the engine is turning or not. That's how the
fuel-injection system for the Lycoming 540 engine in my plane works.

Pete

On Tue, 14 Oct 2003 11:04:46 -0700, "Peter Duniho"
> wrote:


>I'm not sure what exactly is going on here, but I don't think it's
>"hydraulic lock". As a previous post hinted at, "hydraulic lock" is
>something that is specific to only certain kinds of engines (like radials)
>and not those found in C172's. It happens when oil drains into the
>cylinder, putting an incompressible substance into a space that wants to
>compress when the engine turns.
>
>If you are having trouble with the starter not being able to turn the engine
>on a C172, you've either got a dead battery, or something worse is going on.
>
>When you first wrote "hydraulic lock", I actually assumed you meant "vapor
>lock", which is what happens when the fuel in the fuel lines is heated to
>the point of vaporization, preventing it from being pumped to the engine.
>This is the usual problem when starting hot engines, especially fuel
>injected ones (carbureted engines usually have enough fuel in the float bowl
>to let things get sorted out during engine start, so even a little vapor in
>the fuel lines won't cause a problem with starting).
>
>But now it sounds like you did actually mean something other than "vapor
>lock". I'm not sure what it was, but I'm pretty certain that, given that
>you're talking about a C172, it wasn't "hydraulic lock". Even if hydraulic
>lock were possible on a C172, it wouldn't be related to a hot engine start.
>
>> There are actually two fuel pumps, one works with the engine turning,
>> the other is the electric auxiliary pump. So fuel will be pumped to
>> the injectors the moment the engine starts turning.
>
>I'm not familiar with the new fuel-injected C172's, but it's entirely
>possible that with the electric fuel pump running, fuel will be pumped to
>the injectors and even into the engine the moment the fuel pump is turned
>on, regardless of whether the engine is turning or not. That's how the
>fuel-injection system for the Lycoming 540 engine in my plane works.
>
>Pete

Pete, I'm assuming it's hydraulic lock because the starter cranked the
prop around half a turn and then jerked abruptly to a stop. I
re-engaged the starter and it tried to turn the prop but wouldn't. I
waited a second and tried again and it turned the prop another half to
3/4's of a turn and jerked to a stop again.

I did not get out an look to see if gas was pouring out of the exhaust
stacks. But once I advanced to full throttle, the starter, after a
few more attempts, began to turn the engine over at a normal rate.
After a few seconds of this, one of the plugs fired and I thought we'd
be ok, but it still didn't start.

I waited another several seconds and re-engaged the starter and this
time, as it spun the prop, it actually briefly fired up on all
cylinders. I moved quickly to slap the mixture in, as the engine had
quit again but the prop was still windmilling, and just before the
prop stopped, the engine caught for good.

I was an auto mechanic in a previous life and have seen hydraulic lock
before. I know no other way of describing it.

Corky Scott

"Peter Duniho" > wrote in message
...
> "Corky Scott" > wrote in message
> ...
> > With my last experience, the engine actually went into hydraulic lock
> > without me touching the controls or using the auxiliary fuel pump.
> > The prop barely turn half a turn before it stopped and the starter
> > couldn't crank it anymore.
>
> If you are having trouble with the starter not being able to turn the
engine
> on a C172, you've either got a dead battery, or something worse is going
on.

I had the same problem hot-starting a PA32-300 recently. Let sit for a
minute or two, starter was able to crank again. It was the only hot start
I've had to do (so far) in that plane, and the only one where cranking was a
problem. I don't think there's anything wrong with the battery or the
starter, it was some transient condition of the engine.

Jeremy

"Corky Scott" > wrote in message
...
> Pete, I'm assuming it's hydraulic lock because the starter cranked the
> prop around half a turn and then jerked abruptly to a stop. [...]
>
> I was an auto mechanic in a previous life and have seen hydraulic lock
> before. I know no other way of describing it.

Well, like I said, I haven't flown the new C172's, so don't have any
personal experience with that particular engine installation. IMHO, if that
engine IS experiencing hydraulic lock, that's a problem though.

Oil should not be draining into the cylinders. On the 540 engine in my
airplane, excess fuel that gets into the cylinders will drain out the intake
manifold, and then out a valve that leads to the outside of the airplane.
I've made plenty of hot starts, including many that were really flooded
starts (per the technique described by Robert Gary :) ), and never had any
problem with the starter turning over the engine.

I've never experienced anything that could be considered hydraulic lock in
any of the fuel-injected horizontally opposed engines I've ever flown.
That's not a huge number of different airplane/engine combinations (perhaps
a dozen or two over the years), but it's enough that I'd think I'd have
noticed the problem you're describing if it were common and normal.

I can't think of any mechanism by which you'd experience hydraulic lock on
the fuel-injected horizontally opposed engine that's in the new C172, and I
would think that if you DID experience that, it would be worth discussing
with the mechanic who maintains the airplane.

Pete

"Corky Scott" > wrote in message ...

> Pete, I'm assuming it's hydraulic lock because the starter cranked the
> prop around half a turn and then jerked abruptly to a stop.

When you get hydraulic lock in a radial, it's not that the prop starts turning,
it's that the incompressable fluid tries (and succeeds) to expand the cylinder.
You can break a cylinder even pushing the prop through bu hand when oil is present.

"Capt. Doug" > wrote in message >...

snip

> BTW, the Continental system won't bypass fuel back to the tank if the
> mixture is control is closed.

Huh?

Also, most TCM injection systems overhauled/new since about 1995 will
also allow a small amount of fuel into the engine with the mixture at
ICO (unless they've changed the specs again).

TC

On Tue, 14 Oct 2003 15:30:32 -0400, "Ron Natalie" >
wrote:

>
>"Corky Scott" > wrote in message ...
>
>> Pete, I'm assuming it's hydraulic lock because the starter cranked the
>> prop around half a turn and then jerked abruptly to a stop.
>
>When you get hydraulic lock in a radial, it's not that the prop starts turning,
>it's that the incompressable fluid tries (and succeeds) to expand the cylinder.
>You can break a cylinder even pushing the prop through bu hand when oil is present.
>
>
I just called the mechanic on duty for the FBO that maintains the
airplane and described the situation to him. He too thought that it
was probably not hydraulic lock. The time I experienced hydraulic
lock as an auto mechanic was when I pulled a dead Subaru out of a
snowbank where it had been abandoned for a while and dragged it back
to the shop. I was a mechanic and needed a car and thought I could
get the thing running so I pulled it inside and let it warm up. The
starter spun a tiny bit and stopped like the pistons had hit a rock.
I removed the four spark plugs and tried again. This time, geysers of
water shot out of the spark plug holes. One squirt must have traveled
15 feet before it hit the shop wall ten feet up.

I put the spark plugs back in and tried starting it. It did actually
start, but ran so rough, with water spraying out of the radiator that
I immediately shut it off. Busted head gasket, pretty common with the
73 through 76 Subaru's: They had floating cylinder liners.

Anyway, the guy I was talking with claimed no one else had mentioned
this. I ventured that perhaps they just hadn't written it up, since
they always seem to get it running, as I did.

I've never studied the Lycoming starters, but it's possible the
bendix, if it has one, may be popping out prematurely, stopping the
crank sequence. Engine compression would stop the prop spinning very
quickly, since it's a 180 hp model.

But that doesn't adaquately explain why, when I tried to re-engage the
starter, it appeared to have trouble turning the prop. I had to
repeatedly turn the key to "start", again and again and the prop would
turn just a bit and stop. Sometimes it appeared to get over a hump
and turn for one complete revolution, but would then stop again.

I doubt that it's the battery, because when the starter finally
managed to get going, it spun the prop as fast as I've ever seen it
go.

This happened the very first time I tried starting it, when the
airplane had only around 38 hours on it.

The older (but same model 172) has never done this.

Corky Scott

I think he's considering the fact that the starter can't turn the engine
over makes it a hydralic lock. Similar to a hot car engine with the timing
too far advanced. In that case, the spark happens so early that the crank
stops or backs up before it reaches TDC. I wouldn't call that a hydralic
lock though, but I think that's what he is referring to.

The air in the cylinder gets hot and starts expanding as the piston is
trying to compress it as well, and with enough heat, you can get a
preignition from just the air fuel mixture too. Dieseling kind of. Another
example is too much ether in a diesel, a ether lock. Either way, the starter
is unable to overcome the compression of the engine while it is hot.
Quickest way I know around it is to have an assistant, hand-prop-assist the
starter. Safer overall though to just wait for it to cool.


"Peter Duniho" > wrote in message
...
> "Corky Scott" > wrote in message
> ...
> > Pete, I'm assuming it's hydraulic lock because the starter cranked the
> > prop around half a turn and then jerked abruptly to a stop. [...]
> >
> > I was an auto mechanic in a previous life and have seen hydraulic lock
> > before. I know no other way of describing it.
>
> Well, like I said, I haven't flown the new C172's, so don't have any
> personal experience with that particular engine installation. IMHO, if
that
> engine IS experiencing hydraulic lock, that's a problem though.
>
> Oil should not be draining into the cylinders. On the 540 engine in my
> airplane, excess fuel that gets into the cylinders will drain out the
intake
> manifold, and then out a valve that leads to the outside of the airplane.
> I've made plenty of hot starts, including many that were really flooded
> starts (per the technique described by Robert Gary :) ), and never had any
> problem with the starter turning over the engine.
>
> I've never experienced anything that could be considered hydraulic lock in
> any of the fuel-injected horizontally opposed engines I've ever flown.
> That's not a huge number of different airplane/engine combinations
(perhaps
> a dozen or two over the years), but it's enough that I'd think I'd have
> noticed the problem you're describing if it were common and normal.
>
> I can't think of any mechanism by which you'd experience hydraulic lock on
> the fuel-injected horizontally opposed engine that's in the new C172, and
I
> would think that if you DID experience that, it would be worth discussing
> with the mechanic who maintains the airplane.
>
> Pete
>
>

(Corky Scott) wrote in message >...
> On Tue, 14 Oct 2003 11:04:46 -0700, "Peter Duniho"
> > wrote:
> Pete, I'm assuming it's hydraulic lock because the starter cranked the
> prop around half a turn and then jerked abruptly to a stop. I
> re-engaged the starter and it tried to turn the prop but wouldn't. I
> waited a second and tried again and it turned the prop another half to
> 3/4's of a turn and jerked to a stop again.


A modern starter will fix that. I put on a Skytec about a year ago.
The thing spins MUCH faster and stronger.

Corky,

You did describe what sounds like hydraulic lock. It can happen on
horizontally opposed piston engines if the engine is overprimed. You
may have bent a connecting rod.

All the best,
Rick

(Corky Scott) wrote in message >...
> On Tue, 14 Oct 2003 11:04:46 -0700, "Peter Duniho"
> > wrote:
>
>
> >I'm not sure what exactly is going on here, but I don't think it's
> >"hydraulic lock". As a previous post hinted at, "hydraulic lock" is
> >something that is specific to only certain kinds of engines (like radials)
> >and not those found in C172's. It happens when oil drains into the
> >cylinder, putting an incompressible substance into a space that wants to
> >compress when the engine turns.
> >
> >If you are having trouble with the starter not being able to turn the engine
> >on a C172, you've either got a dead battery, or something worse is going on.
> >
> >When you first wrote "hydraulic lock", I actually assumed you meant "vapor
> >lock", which is what happens when the fuel in the fuel lines is heated to
> >the point of vaporization, preventing it from being pumped to the engine.
> >This is the usual problem when starting hot engines, especially fuel
> >injected ones (carbureted engines usually have enough fuel in the float bowl
> >to let things get sorted out during engine start, so even a little vapor in
> >the fuel lines won't cause a problem with starting).
> >
> >But now it sounds like you did actually mean something other than "vapor
> >lock". I'm not sure what it was, but I'm pretty certain that, given that
> >you're talking about a C172, it wasn't "hydraulic lock". Even if hydraulic
> >lock were possible on a C172, it wouldn't be related to a hot engine start.
> >
> >> There are actually two fuel pumps, one works with the engine turning,
> >> the other is the electric auxiliary pump. So fuel will be pumped to
> >> the injectors the moment the engine starts turning.
> >
> >I'm not familiar with the new fuel-injected C172's, but it's entirely
> >possible that with the electric fuel pump running, fuel will be pumped to
> >the injectors and even into the engine the moment the fuel pump is turned
> >on, regardless of whether the engine is turning or not. That's how the
> >fuel-injection system for the Lycoming 540 engine in my plane works.
> >
> >Pete
>
> Pete, I'm assuming it's hydraulic lock because the starter cranked the
> prop around half a turn and then jerked abruptly to a stop. I
> re-engaged the starter and it tried to turn the prop but wouldn't. I
> waited a second and tried again and it turned the prop another half to
> 3/4's of a turn and jerked to a stop again.
>
> I did not get out an look to see if gas was pouring out of the exhaust
> stacks. But once I advanced to full throttle, the starter, after a
> few more attempts, began to turn the engine over at a normal rate.
> After a few seconds of this, one of the plugs fired and I thought we'd
> be ok, but it still didn't start.
>
> I waited another several seconds and re-engaged the starter and this
> time, as it spun the prop, it actually briefly fired up on all
> cylinders. I moved quickly to slap the mixture in, as the engine had
> quit again but the prop was still windmilling, and just before the
> prop stopped, the engine caught for good.
>
> I was an auto mechanic in a previous life and have seen hydraulic lock
> before. I know no other way of describing it.
>
> Corky Scott

Rick Durden wrote:
>
> You may have bent a connecting rod.

I think that unlikely considering the quality of the flight after he did get it
started.

George Patterson
A woman's perfect breakfast occurs when she's sitting at the table sipping
gourmet coffee while looking at pictures of her son on the cover of Sports
Illustrated, her daughter on the cover of Business Week, her boyfriend on
the cover of Playgirl, and her husband on the back of the milk carton.

On 14 Oct 2003 18:35:19 -0700, (Rick Durden)
wrote:

>Corky,
>
>You did describe what sounds like hydraulic lock. It can happen on
>horizontally opposed piston engines if the engine is overprimed. You
>may have bent a connecting rod.
>
>All the best,
>Rick

I sure hope not. The engine did start and run normally after that,
with no vibration or noises.

I did mention that I did not use the auxiliary fuel pump for the start
didn't I? Repeat, did NOT use the auxiliary fuel pump.

All I did was crack the throttle and attempt the start. I do not know
for how long the airplane was sitting prior to me getting there but
the engine was hot to the touch. There should have been no residual
fuel in the combustion chambers, unless the injectors somehow leaked
down after the shutdown. This engine is virtually brand new so I'd
hope the injectors aren't leaking down.

Corky Scott

George,

Damage from hydraulic lock sometimes shows up immediately (friend of
mine had the engine fail within 45 minutes after the lock) and some
does not show up for many hours, or even until overhaul. I just hope
he did not damage the engine.

All the best,
Rick

"G.R. Patterson III" > wrote in message >...
> Rick Durden wrote:
> >
> > You may have bent a connecting rod.
>
> I think that unlikely considering the quality of the flight after he did get it
> started.
>
> George Patterson
> A woman's perfect breakfast occurs when she's sitting at the table sipping
> gourmet coffee while looking at pictures of her son on the cover of Sports
> Illustrated, her daughter on the cover of Business Week, her boyfriend on
> the cover of Playgirl, and her husband on the back of the milk carton.

Rick Durden wrote:
>
> Damage from hydraulic lock sometimes shows up immediately (friend of
> mine had the engine fail within 45 minutes after the lock) and some
> does not show up for many hours, or even until overhaul.

I'm just thinking that a bent con-rod should show up as vibration. At the least,
you'll be getting less compression and power out of that cylinder.

George Patterson
A woman's perfect breakfast occurs when she's sitting at the table sipping
gourmet coffee while looking at pictures of her son on the cover of Sports
Illustrated, her daughter on the cover of Business Week, her boyfriend on
the cover of Playgirl, and her husband on the back of the milk carton.

Corky,

Thanks for the clarification. Not using the boost pump would tend to
rule out a hydraulic lock event on a horizontally opposed engine.

All the best,
Rick

(Corky Scott) wrote in message >...
> On 14 Oct 2003 18:35:19 -0700, (Rick Durden)
> wrote:
>
> >Corky,
> >
> >You did describe what sounds like hydraulic lock. It can happen on
> >horizontally opposed piston engines if the engine is overprimed. You
> >may have bent a connecting rod.
> >
> >All the best,
> >Rick
>
> I sure hope not. The engine did start and run normally after that,
> with no vibration or noises.
>
> I did mention that I did not use the auxiliary fuel pump for the start
> didn't I? Repeat, did NOT use the auxiliary fuel pump.
>
> All I did was crack the throttle and attempt the start. I do not know
> for how long the airplane was sitting prior to me getting there but
> the engine was hot to the touch. There should have been no residual
> fuel in the combustion chambers, unless the injectors somehow leaked
> down after the shutdown. This engine is virtually brand new so I'd
> hope the injectors aren't leaking down.
>
> Corky Scott

"Paul Sengupta" > wrote in message >...
snip

> How does it happen to be that the standard hot start procedure for
> my plane (fuel injected Lycoming 360) and I believe many others is:
> no priming, throttle to max, mixture to idle cut off and crank...when it
> fires reverse the throttle and mixture (works like a dream on my plane
> by the way). Now this is basically the flooded engine procedure...
> so how come there's fuel in the cylinders/manifold on shutting down a
> FI engine by leaning the mixture?

Fuel "out" of the servo is shut off by the mixture control at ICO. If
the Brand L in question has an external flow divider, the valve in the
flow divider closes also.

The engine quits because of the "finger over the soda straw"
principle, there is still fuel in the injector hard lines, it just
stops flowing out the nozzle end when the inlet end is stopped up.

The heat-soaked engine compartment eventually drives the fuel out of
the hard lines either as liquid fuel, or more likely as fuel vapor.
Catch it just right and you can hear it "bubbling".

Fuel ends up in the intake port of the cylinder, or in the induction
system, where it is waiting patiently for a suck-squeeze-spark.

TC

Here's the way I was taught to hot-start the 180hp Lycomings in the Skyhawk:
Follow the check list procedure for a normal (first time today)
start.....

That is:
Advance throttle 1/4 inch
Mixture to idle cutoff
Master switch on
Fuel pump on
Push in mixture control to see positive fuel flow on the gauge
Mixture to idle cutoff
Fuel pump off
Crank the engine
Shove the mixture control to full rich when the engine starts
Adjust throttle for 1,000rpm

It works for me. Even when the OAT is 3-digits

Hot start procedure for my Trinidad (Lycoming IO 540 C4 DD 250hp) is
fuel pump on, throttle full open, mixture to full rich for 1 second or
positive flow then closed, fuel pump off, and when the engine fires
mixture to full rich. Simple & works every time.

Bex


--
bex
------------------------------------------------------------------------
Posted via OziPilots Online [ http://www.OziPilotsOnline.com.au ]
- A website for Australian Pilots regardless of when, why, or what they fly -

Ah, thanks! The follow on question is then...

We stop the engine by moving the mixture to ICO. Now all
the books, etc, say that this is so that there is no fuel left to
ignite if there's a live mag, so the engine won't start. Now if
an FI engine leaves fuel ready for the next start, then a) it's
more dangerous if there's a live mag, and b) would switching
off the ingition be any different in this case? Would it leave
the engine too flooded?

Paul

> wrote in message
om...
> The heat-soaked engine compartment eventually drives the fuel out of
> the hard lines either as liquid fuel, or more likely as fuel vapor.
> Catch it just right and you can hear it "bubbling".

On Fri, 17 Oct 2003 03:40:48 GMT, "Casey Wilson" >
wrote:

>
>Here's the way I was taught to hot-start the 180hp Lycomings in the Skyhawk:
> Follow the check list procedure for a normal (first time today)
>start.....
>
>That is:
>Advance throttle 1/4 inch
>Mixture to idle cutoff
>Master switch on
>Fuel pump on
>Push in mixture control to see positive fuel flow on the gauge
>Mixture to idle cutoff
>Fuel pump off
>Crank the engine
>Shove the mixture control to full rich when the engine starts
>Adjust throttle for 1,000rpm
>
>It works for me. Even when the OAT is 3-digits
>
>
>
Casey, you just described what the Skyhawk POH says is the "cold
start" procedure.

The POH specifically says to eliminate the use of the fuel pump for a
hot start.

Did you read that out of the POH, or is it something taught to you by
your instructor because he/she found it worked better?

Thanks, Corky Scott

"Corky Scott" > wrote in message
...
> On Fri, 17 Oct 2003 03:40:48 GMT, "Casey Wilson" >
> wrote:
>
> >
> >Here's the way I was taught to hot-start the 180hp Lycomings in the
Skyhawk:
> > Follow the check list procedure for a normal (first time today)
> >start.....
> >
> >That is:
> >Advance throttle 1/4 inch
> >Mixture to idle cutoff
> >Master switch on
> >Fuel pump on
> >Push in mixture control to see positive fuel flow on the gauge
> >Mixture to idle cutoff
> >Fuel pump off
> >Crank the engine
> >Shove the mixture control to full rich when the engine starts
> >Adjust throttle for 1,000rpm
> >
> >It works for me. Even when the OAT is 3-digits
> >
> >
> >
> Casey, you just described what the Skyhawk POH says is the "cold
> start" procedure.
>
> The POH specifically says to eliminate the use of the fuel pump for a
> hot start.
>
> Did you read that out of the POH, or is it something taught to you by
> your instructor because he/she found it worked better?

The latter. After ten frustrating minutes sitting at the fuel pump after
a couple of hours of dual instrument work, I was ready to get the towbar out
and drag the ^%$#(@% airplane back to the tiedown. All the time the
instructor was sitting in the right seat, not saying a word.
Finally, he said, "Had enough?"
"%&&#)&@&&, right," says I.
"Use the checklist for a cold start."
Less than a minute later we were rolling across the ramp. He told me
later that he let me get frustrated to make the lesson more firm.
This, by the way, is the only deviation from the POH I've ever used
intentionally.

"Casey Wilson" > wrote in message ...
>
> > >
> > Did you read that out of the POH, or is it something taught to you by
> > your instructor because he/she found it worked better?
>
> The latter. After ten frustrating minutes sitting at the fuel pump after
> a couple of hours of dual instrument work, I was ready to get the towbar out
> and drag the ^%$#(@% airplane back to the tiedown.

The book starting procedure for my (pressure carb'd lycoming) never worked
either (especially when warm). My former mechanic (who never read a book
or checklist in his life, generally one of his failings), never had a problem starting
hot or cold. So I asked him what he did, and that's what I use for everything:

1. If cold (boost on, prime, boost off).
2. Full Rich, 1/4" thorttle.
3. Crank (two blades before the mag comes on if cold).

Always worked. This is neither the book hot start or cold start procedure
(both of which call for leaving the boost pump on).

"Paul Sengupta" > wrote in message >...

> We stop the engine by moving the mixture to ICO. Now all
> the books, etc, say that this is so that there is no fuel left to
> ignite if there's a live mag, so the engine won't start. Now if
> an FI engine leaves fuel ready for the next start, then a) it's
> more dangerous if there's a live mag, and b) would switching
> off the ingition be any different in this case? Would it leave
> the engine too flooded?

OK, so the engine is running and you switch off the mags, then the
mixture.

The air/fuel that is left in the induction system would be real close
to an ideal mixture for a "hot-start" seeing how it was working so
well when you flipped off ignition. The additional fuel added from
the hard lines would probably initially enrich the mixture, but would
be just as likely to help keep the right amount of fuel in the system
for a longer period of time.

With an ICO shut-down, initially there is no fuel, then gradually goes
to too lean, gets richer, then leans out again as the fuel evaporates.

The trick for an injected Lycoming hot start is to try the first one
without adding any fuel, then add a little. Too lean is easily
remedied, too rich/flooded is more problematic to clear.

TC

Well said. A lean mixture is easier to richen and ignite. Rich is a
pain.

> The trick for an injected Lycoming hot start is to try the first one
> without adding any fuel, then add a little. Too lean is easily
> remedied, too rich/flooded is more problematic to clear.
>
> TC