Art of Choke/Choking

[mshmodela]

still learning how to start my Model A and looking at this:

http://www.modelabasics.com/carb%20basics%202.htm

I can envision the idea of the choke plate is much like one holding their thumb on the end of a garden hose, only backwards (increasing vacuum, as apposed to output water pressure (speed) with the garden hose. Now if fully choked the intake of air supply is what totally cut --and why one can only hold the choke out (enabled) for a few cycle of the engine turning... Now if an engine fails to start after say fully choked for 3 engine turns, should one then stop and try without choking?? (assumed a cold engine)...

Also, if you feel you flooded the engine, aside from waiting, would one use the carburetor drain plug to speed up that process or? Maybe turn off the fuel and cycle the engine a few times to expel the fuel laden mixture ?

-Mike
Cleveland

[jthomas6]

Originally Posted by mshmodela

Also, if you feel you flooded the engine, aside from waiting, would one use the carburetor drain plug to speed up that process or? May turn off the fuel and cycle the engine a few times to expel the fuel laden mixture ?

-Mike
Cleveland

If I have flooded the engine (like tried to choke to start BUT forgot to turn the key on ), I put spark advance full up and throttle full down. Crank, and be prepared to quickly put throttle mostly up. A flooded engine will 'usually' fire with full throttle.

Joe

[Patrick L.]

As you get used to this starting this monster, you'll know how to use the choke regarding air and engine temps. Colder air requires more/longer choke.
When starting the spark lever should be retarded/up.
Draining the carburetor will not help starting a flooded engine. Adding just tad of spark advance may help, but, opening the throttle and adding air is a must. If an engine is really flooded the sparklers may need to be removed/dried and the engine turned over a bit to dry the cylinders.
There are some folks that will try to tell you that an updraft engine can't be flooded, just nod and back away slowly.

[johnbuckley]

I agree with #2. and don't mess with the drain plug- easy to cause subsequent leaks or misthread it .
A's that are reasonably well set up are generally easy starters and if not started within a few goes it is likely to be something other than just choke manipulation that causing the problem

[stainless steve]

I always crank mine first to see if it will lite ....then and only then do I pull the choke out

[Mitch//pa]

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a finely tuned engine only needs to be choked for a split second cold. as fast as i pull it thats as fast i release it.

[Terry,NJ]

Over choking an engine, any engine, will cause a carbon build up. As has been said, the less the better, but it's there for when it's needed. And as has been said, if it's flooded, Hold the throttle wide open to get enough air to offset the extra gas. If you should get a flame out of the carburetor (unlikely) keep cranking till it starts! The vacuum will put the flames out.
Terry

[CarlG]

The title to this thread sounds like a chapter in "Murder 101"

[1crosscut]

If you do end up pulling the spark plugs and cranking it over to dry it out be sure to do so with the ignition OFF. If you happen to have one of the spark plug wires hanging over the open hole and it sparks across to the engine you can have a fountain of flame erupt out of one of your spark plug holes.

[marc hildebrant]

The Model A engine is real easy to flood.

I use the choke for only two revs and then release it. Fires up 99 % of the times.

If flooded, throttle wide open and crank...should fire up.

Do not choke more than two revs as it will flood.

Marc

[steve s]

I always thought that choking for four "grunts" (BUT NO MORE!) was the way to go: one intake stroke to load up each cylinder.

[Fred K-OR]

I also agree with #2 above. Just another tip is that if you pull the choke, push the starter and nothing happened within a couple of revs of the engine, stop choking. Let it set for a few seconds, then try same again. If no results, then do what # 2 said above.

[newshirt]

Originally Posted by Mitch//pa

a finely tuned engine only needs to be choked for a split second cold. as fast as i pull it thats as fast i release it.

That's exactly what I do. Snap it out, and right back in again. And never when warm. But every engine is different.

[H. L. Chauvin]

Hi MSH,

Some different carburetors, like with different Sears Model A Marvels, some different Model A Tillotstons, and/or different Model A Zeniths, each individual carburetor may react differently during startups in varying temperatures.

On my present Model B carburetor, (w/Model B distributor & 3X plugs), for a cold start, I open gas line, turn on switch, pull out choke, allow engine to turn one revolution, release choke, off it goes every time in ambient temperatures from about 22 degrees F to about 100 degrees F.

With engine still warm after not running for about (1) minute to (20) minutes in warm weather, with no choke, hit starter rod & it starts on first revolution.

Added benefit for providing accurate tune ups with rebuilt carburetors & rebuilt distributors & having clean spark plugs, is that a Model A starter can last well over 25 years -- however, with starter grinding for a long time & building up heat, starters wear very rapidly.

[ericr]

Originally Posted by H. L. Chauvin

Hi MSH,

Some different carburetors, like with different Sears Model A Marvels, some different Model A Tillotstons, and/or different Model A Zeniths, each individual carburetor may react differently during startups in varying temperatures.

On my present Model B carburetor, (w/Model B distributor & 3X plugs), for a cold start, I open gas line, turn on switch, pull out choke, allow engine to turn one revolution, release choke, off it goes every time in ambient temperatures from about 22 degrees F to about 100 degrees F.

With engine still warm after not running for about (1) minute to (20) minutes in warm weather, with no choke, hit starter rod & it starts on first revolution.

Added benefit for providing accurate tune ups with rebuilt carburetors & rebuilt distributors & having clean spark plugs, is that a Model A starter can last well over 25 years -- however, with starter grinding for a long time & building up heat, starters wear very rapidly.

H.L., have you ever heard of stopping a Model A by pulling out the choke till the engine stops? It makes starting next time very easy.

[Tom Wesenberg]

Originally Posted by ericr

H.L., have you ever heard of stopping a Model A by pulling out the choke till the engine stops? It makes starting next time very easy.

It will also wash the oil off the cylinder walls.

[H. L. Chauvin]

Hi ericr,

Never heard of someone "recommending" choking to stop a Model A engine with its constant gravity flow of fuel .

Sounds like a possible fire hazard with gasoline possibly dripping out of the carburetor adjacent to a hot manifold & muffler especially with an attached extended paper carburetor air filter.

Did hear of one guy who did "try" same -- he choked his engine to stop it, had gasoline run into his muffler & heat from the red hot muffler cause a loud back fire.

Also heard of one guy cranking & cranking a cold engine with switch "OFF" & choke pulled -- while not thinking, he next turned switch "ON", hit starter rod & his engine started & his gasoline filled muffler exploded.

Old time Model A stories are numerous.

Anyway, always kept my A's well tuned.

Even years ago as a teenager when I could not afford new batteries for my $25.00 Model A, I cranked when I had weak batteries.

A. With engine cold, 1/4 engine turn with crank & choke pulled, then next 1/4 turn un-choked meant start.

B. With engine warm, 1/4 turn with crank & no choke meant start.

If contents of paragraph A. and/or B. did not work as indicated above, this meant it was time to clean corrosion off of all distributor component electrical connections & clean coil electrical connections, plus run point file through points, all caused by high humidity while parking on bare ground with water table only one (1) foot below.

Because of daily constant Model A use back then, gas tank & carburetor stayed clean enough with just the fine screen filter in the glass sediment bowl.

[tbirdtbird]

all has been answered. just to confirm that the way to start ANY flooded engine is to put the gas pedal all the way to the floor and crank (in this case throttle rod all the way down). This may seem counter-intuitive. But carb jets will deliver little fuel at cranking speed. With the butterfly wide open, way more air is being admitted than fuel and thus the cylinders will clear out. When it catches and runs be ready to back the gas off quickly

[Marco Tahtaras]

Originally Posted by H. L. Chauvin

Hi MSH,

Some different carburetors, like with different Sears Model A Marvels, some different Model A Tillotstons, and/or different Model A Zeniths, each individual carburetor may react differently during startups in varying temperatures.

On my present Model B carburetor, (w/Model B distributor & 3X plugs), for a cold start, I open gas line, turn on switch, pull out choke, allow engine to turn one revolution, release choke, off it goes every time in ambient temperatures from about 22 degrees F to about 100 degrees F.

With engine still warm after not running for about (1) minute to (20) minutes in warm weather, with no choke, hit starter rod & it starts on first revolution.

Added benefit for providing accurate tune ups with rebuilt carburetors & rebuilt distributors & having clean spark plugs, is that a Model A starter can last well over 25 years -- however, with starter grinding for a long time & building up heat, starters wear very rapidly.

Hi Henry,
Are you actually turning it through four compression strokes? The max I've ever done is two and if it's a strange car (somebody else's) I do a quick check of a couple things before repeating as it shouldn't fail if all is normal.

I haven't run a "B" carb but wouldn't expect it to produce less gas.

[H. L. Chauvin]

Hi Marco,

A. I think one full 360 degree revolution is usually the two (2) compression strokes you are mentioning.

B. For an experiment, if one has a slightly weak battery, one can open the hood, press the starter rod, & actually "clearly" see each individual revolution of the engine fan .... as well as "hear" each of the engine's individual revolutions.

C. With a cold engine, i.e., parked for a time, normal gas/air mixture in all four combustion chambers have already evaporated; hence, a cold engine will usually not start on the first engine 360 degree revolution.

D. However, with a cold engine with the choke pulled before the first revolution, on this first revolution, at "least" one (1) of the four cylinders will experience the intake stroke & this combustion chamber will get fuel.

E. At the end of this first revolution, the choke is immediately release ..... (with a fully charged battery, & engine turning rapidly, one has to be quick to release the choke after one revolution).

F. Next with the starter continuing to rotate the engine without stopping, the fueled combustion chamber will enter into the compressions stroke where right BTDC, the plug will fire & ignite the fuel in the combustion chamber & can start the engine with at least this one cylinder.

G. On a warm engine, one can experience that the engine easily can start in the first revolution.