Wisdom of Stopping Engine by Choking It Out

[ericr]

is this practice harmful to the engine in any way? Sure makes re-starting easier, though.....

[GRutter]

I can't see where filling the combustion chambers and exhaust with a fuel-rich mixture would be in the best interests of your engine.

[Chuck Sea/Tac]

Sounds like an old wives tale. Wether it would actually wash the cylinders a little, I don’t know, it it makes me cringe just thinking about it.!

[Ruth]

I wouldn't. As mentioned it will wash the oil off of the cylinders. Any excess gas is going to end up in the oil pan, eventually diluting the oil. No not a good idea.

[McMimmcs]

My mechanic father often said only a novice would do such a foolish trick.

[1930-Pickup]

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With aircraft reciprocating engines, the FAA instructs that the proper way to shut the engine down is to close off the fuel and let the engine run until it stops. There is a good reason for doing it this way.

When you 'choke the engine to death' your introducing too much fuel into the combustion chamber. It washes the oil off the cylinder walls, which increases ring/cylinder wear at the next start up. The extra fuel can also run past the rings and dilute the oil in the crankcase.

[1930-Pickup]

Originally Posted by McMimmcs

My mechanic father often said only a novice would do such a foolish trick.

Totally agree.
But why did he have to say this often??
Were his kids never listening to him?

[Russ/40]

A healthy "A" engine is the easiest engine to start I have ever experienced. Someone, can't remember whow, on this forum once said, "an "A" engine wants to run". That has been my experience. The only time I choke mine is on the first start of the day.

[Bill G]

Choking would not be good to stop the engine. If you're going to choke, then why not when starting?

[Chris in WNC]

growing up on the farm in the 1950s-60s, we had a 1938 Allis-Chalmers styled WC tractor.
sometime before my memories began, the magneto ground which stopped the engine broke or otherwise went south.
my Grandpa, a pragmatic non-mechanic, simply choked the engine to stop it every time he used it.
that tractor worked hard up into the 1970s and saw limited service into the 80's.
the engine was never taken apart and did not smoke or knock.
last time I saw it, a buyer was driving it home across the fields from Grandpa's estate auction in 1984.
I suppose it's comparing apples to oranges, but evidently choking it didn't do too much damage.

[McMimmcs]

Originally Posted by 1930-Pickup

Totally agree.
But why did he have to say this often??
Were his kids never listening to him?

He said it often to his customers, not his kids!

[ericr]

Originally Posted by McMimmcs

My mechanic father often said only a novice would do such a foolish trick.

hhmmm....what did he think about turning the ignition off and on while driving to make it backfire?

[McMimmcs]

Originally Posted by ericr

hhmmm....what did he think about turning the ignition off and on while driving to make it backfire?

He said only idiots do that!

[Chuck Sea/Tac]

Yes, but those idiots were having fun. Assuming they didn’t have to buy the new muffler!

[Aarongriffey]

I remember back in the day seeing folks rev up their engine real fast and shuting the ignition off. Especially in the winter time.
I remember a guy shutting is tractor off at full throttle when it was belted to a silo filler.
It kept turning over a long time with the silo filler acting as a flywheel.

[McMimmcs]

[QUOTE=Chuck Sea/Tac;1931750]Yes, but those idiots were having fun. Assuming they didn’t have to buy the new muffler![/QUOTE

They should have had to work for it.

[McMimmcs]

Originally Posted by Chuck Sea/Tac

Yes, but those idiots were having fun. Assuming they didn’t have to buy the new muffler!

The expense of a new muffler often showed how stupid they really were! Driving the family car was fun, damaging it showed a lack of common sense !

[Big hammer]

Originally Posted by ericr

is this practice harmful to the engine in any way? Sure makes re-starting easier, though.....

I pull the choke and release it after 2 turn overs and it's running! IMO you might have issues that need you attention if your having problems starting. When my grandsons 1/4 midgets wouldn't start with 1 or2 cranks I would pull the plug and replace it, the old one I then would clean, file the ground flat, gap and it was ready. These engines where Honda 4 hp engined stock, race illegal they put out over 8 hp on a dyno ! Fun times!!

[Kurt in NJ]

when starting was with a hand crank loading the cylinders with fuel was prep for starting, hoping it would start on spark----old time lore along with "kicking the tires" which is leftover from clincher rims, kicking them to see that the bead is seated

[BRENT in 10-uh-C]

Originally Posted by Ruth

I wouldn't. As mentioned it will wash the oil off of the cylinders. Any excess gas is going to end up in the oil pan, eventually diluting the oil. No not a good idea.

Originally Posted by Chuck Sea/Tac

Sounds like an old wives tale. Whether it would actually wash the cylinders a little, I don’t know, it it makes me cringe just thinking about it.!

Just to muddy up the waters here a bit. Ponder these thoughts for a bit;

.. ~ If gasoline typically evaporates when exposed to heat, what happens when a teaspoon, --or maybe two drips into a gallon of hot oil? Does it evaporate or does it dilute the oil?

.. ~ If it does dilute the oil, how much does it dilute it, -how long does the dilution last, -and what are the effects of this amount of dilution??

.. ~ If it does not evaporate before the engine cools, does it evaporate the next time the engine is at operating temperature? Did it evaporate in one or more cylinders due to a hot piston, or cylinder wall, -or a combustion chamber roof giving off heat just as the engine stopped running?

.. ~ If the gasoline finds its way past the first ring gap, and goes to the second ring gap, -is there enough liquid gasoline left to actually dilute any residual oil on the cylinder walls? If it does dilute the oil as the fuel drips, does it dilute the entire 360° circumference of the cylinder bore, or maybe one small little area?

.. ~ When an engine stops operating due to the ignition source stopping, what happens to the gasoline/air mixture left unburned in each cylinder?

.. ~ When a running engine is stopped, how long does it take before rust starts forming on the cylinder walls and piston rings. What happens to that rust when the engine is restarted?



I guess I view much of this question as we have always been told not to do this because it sounds believable that it would harm something, ...but in the grande scheme of things, I truly believe there is little, -if any, noticeable damage done using the choke to stop an engine from running.



.
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[ericr]

Originally Posted by BRENT in 10-uh-C

Just to muddy up the waters here a bit. Ponder these thoughts for a bit;

.. ~ If gasoline typically evaporates when exposed to heat, what happens when a teaspoon, --or maybe two drips into a gallon of hot oil? Does it evaporate or does it dilute the oil?

.. ~ If it does dilute the oil, how much does it dilute it, -how long does the dilution last, -and what are the effects of this amount of dilution??

.. ~ If it does not evaporate before the engine cools, does it evaporate the next time the engine is at operating temperature? Did it evaporate in one or more cylinders due to a hot piston, or cylinder wall, -or a combustion chamber roof giving off heat just as the engine stopped running?

.. ~ If the gasoline finds its way past the first ring gap, and goes to the second ring gap, -is there enough liquid gasoline left to actually dilute any residual oil on the cylinder walls? If it does dilute the oil as the fuel drips, does it dilute the entire 360° circumference of the cylinder bore, or maybe one small little area?

.. ~ When an engine stops operating due to the ignition source stopping, what happens to the gasoline/air mixture left unburned in each cylinder?

.. ~ When a running engine is stopped, how long does it take before rust starts forming on the cylinder walls and piston rings. What happens to that rust when the engine is restarted?



I guess I view much of this question as we have always been told not to do this because it sounds believable that it would harm something, ...but in the grande scheme of things, I truly believe there is little, -if any, noticeable damage done using the choke to stop an engine from running.



.
.

well there would still be some cylinder and valve rotation as the engine conked out, wouldn't some gas get expelled through the exhaust valves?

[Hitman]

Lots of armchair opinions within, and yet these cars have managed to survive 90 years with all sorts of abuse and neglect.

Choking the engine to kill it will do absolutely no harm to the engine, maybe the plugs overtime. We're talking about such a minimal amount of fuel that is transmitted in a near vapor form. And from maybe 800 rpm to 0 in a matter of seconds.

If you were so concerned, you wouldn't choke the engine to start it, and you'd kill the fuel, to stop the engine. Turning off the ignition just takes away the spark, it still allows fuel into the cylinders without burning.

[Ruth]

Originally Posted by BRENT in 10-uh-C

Just to muddy up the waters here a bit. Ponder these thoughts for a bit;

.. ~ If gasoline typically evaporates when exposed to heat, what happens when a teaspoon, --or maybe two drips into a gallon of hot oil? Does it evaporate or does it dilute the oil?

.. ~ If it does dilute the oil, how much does it dilute it, -how long does the dilution last, -and what are the effects of this amount of dilution??

.. ~ If it does not evaporate before the engine cools, does it evaporate the next time the engine is at operating temperature? Did it evaporate in one or more cylinders due to a hot piston, or cylinder wall, -or a combustion chamber roof giving off heat just as the engine stopped running?

.. ~ If the gasoline finds its way past the first ring gap, and goes to the second ring gap, -is there enough liquid gasoline left to actually dilute any residual oil on the cylinder walls? If it does dilute the oil as the fuel drips, does it dilute the entire 360° circumference of the cylinder bore, or maybe one small little area?

.. ~ When an engine stops operating due to the ignition source stopping, what happens to the gasoline/air mixture left unburned in each cylinder?

.. ~ When a running engine is stopped, how long does it take before rust starts forming on the cylinder walls and piston rings. What happens to that rust when the engine is restarted?



I guess I view much of this question as we have always been told not to do this because it sounds believable that it would harm something, ...but in the grande scheme of things, I truly believe there is little, -if any, noticeable damage done using the choke to stop an engine from running.

OK look at the other side. If that gas were to evaporate, how is the going to help the engine on re-start?

I never mentioned rust, my concern was dry cylinders. And where is the gas going to evaporate to in a cylinder with the valves closed?

i think I will continue to let the carburetor run dry.

[redmodelt]

If you choke it, you are cutting off its air supply.

[BRENT in 10-uh-C]

Originally Posted by Ruth

OK look at the other side. If that gas were to evaporate, how is the going to help the engine on re-start?

I never mentioned rust, my concern was dry cylinders. And where is the gas going to evaporate to in a cylinder with the valves closed?

i think I will continue to let the carburetor run dry.

I am not necessarily disputing or disagreeing with you on the 'restart' assistance.

I agree you never mentioned rust however I have looked at many cylinders doing inspections and they tend to rust, -even when the valve appear to be seated. This would tend to indicate there is a lack of oil there anyway. The skirts when cold have not expanded enough to create friction like they would when the engine is running. By the time an A engine has started, the rods have splashed enough oil where it is no longer an issue for the lower cylinder walls.

As far as where the evaporated fuel goes, my theory is it goes to the same place as where the compression goes when an engine is stopped. It slowly escapes past the ring gaps.

[Ruth]

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Originally Posted by BRENT in 10-uh-C

As far as where the evaporated fuel goes, my theory is it goes to the same place as where the compression goes when an engine is stopped. It slowly escapes past the ring gaps.

Exactly.

[Benson]

delete

[40 Deluxe]

Another point to ponder: In the days of carburetors it was common to find excessive cylinder wall wear at the top, to the extent that a ridge reamer was standard equipment in every mechanic's toolbox. This ridge was often in evidence before 100,000 miles. Now you will see the factory hone crosshatch clear to the top of the cylinders after 300,000 miles-no ridge! I think fuel injection has a lot to do with this. With a carburetor, a choke was needed for cold starts, resulting in a lot of raw gas (liquid fuel does not burn) washing down the cylinders, causing excess wear. With electronic injection, fuel is atomized at approx. 50 psi. The computer richens the mixture, but the air is not choked off so the cylinders are not washed down.

[katy]

Methinks that a lot of the longevity of modern engines is in the use of superior metals in the construction.

[BRENT in 10-uh-C]

Originally Posted by katy

Methinks that a lot of the longevity of modern engines is in the use of superior metals in the construction.

Yes very true about superior metals and machining, -and add synthetic oils to the reason for better longevity too, ...not so much on the fuel injection.

[Apperloo]

Right or wrong I turn off the gas cock and let it burn up the fuel.
Keeps the fumes down a bit in the garage.

[Will N]

Originally Posted by Aarongriffey

I remember back in the day seeing folks rev up their engine real fast and shuting the ignition off. Especially in the winter time.
I remember a guy shutting is tractor off at full throttle when it was belted to a silo filler.
It kept turning over a long time with the silo filler acting as a flywheel.

Yup, my father used to do the same thing. He felt it made it easier to restart with a charge of gas in the cylinders. But he stopped doing that when they started putting smog crap on the engines in the early '70s. They were prone to dieseling after switching off the ignition, and goosing it before shutting it off just made it worse.

[Patrick L.]

I don't have much of an issue with shutting down by choking, but, I have to ask why.

That doesn't make sense to me. On a cold start the choke is pulled anyway, so why pull it twice. To shut the engine down I give a twist to the key, its easier.