electric choke

Starting My Big block with an electric choke..sat overnight or days , whatever, engine is cold. Choke is set and car starts nicely but the choke flapper (my definition) opens up completely after about 25 seconds and the engine wants to stall. Is this a normal time for it to open or can that be adjusted. New pro-form 850 double pumper. Thanks in advance. Thanks Moparts

Choke pull-off is usually a matter of minutes, not seconds.

A simple adjustment of the choke affects how long the choke stays on. Best way to see it is to check a YouTube video.

https://www.youtube.com/watch?v=0H5IBSFgYJE

Adjust the choke housing.

And be aware that if you turn on the ignition switch for a time before starting the motor, the internal heater will be on and will make the choke pull off sooner.

Saw that before..did it and no matter where I set the butterfly it opens within seconds. IF I adjust the butterfly so it is closed,( just closed barely as the instructions say) the engine smokes and stutters until the choke opens up a bit. If I leave the butterfly an 1/8 inch or so open..the motor starts and the choke works for about 15 seconds and then the car stalls. ( butterfly now almost completely open)Restart and it's like a cold motor with no choke and unless RPM's are kept up, it will stall.

You might want to replace the choke pulloff.

The choke pull off is inside the electric choke.

Excuse me for not refering to the electrical part of the choke correctly. Is choke thermostat the right term?

choke pull off is for the initial kick open, the housing/spring adjusts how long it takes to go from initial kick to full open.

I'm no expert but I've just been through this myself, so it means I haven't forgotten it yet.

I assume that when the engine is warm and the choke is full open, it starts and idles OK- idle speed is set, idle mixture screws are set.

The video below includes a few more details like setting the initial choke position and working with the fast idle screw. I'd say check it out before you replace anything because it's possible you just have the choke set way too lean because you're trying to hold the choke butterfly open a little when it's cold using the choke spring itself.

Rich/lean tuning adjustments to the choke housing then affect how long it takes the butterfly to open, but it always starts closed when cold.

https://www.holley.com/blog/post/how_to_adjust_the_choke_and_fast_idle_on_holley_carburetors/

Exactly how are you setting the initial position of the choke butterfly? By rotating the choke housing?

Exactly as shown in video and the same as I have done for 57 years

The non running closed position is tight against the tower. As soon as it fires the vacuum kick pulls it to the initial running setting. If you have the housing rotated so that the butterfly isn't snapped tight against the choke tower your set to lean on the housing.

I am not a holley expert, but the carter choke has you adjust the fast idle cam rod to choke to get the choke valve position set to spec. You also adjust the pull off via the choke rod.

So the questions I have is the piston stuck? So that vacuum does not pull it into the housing and open choke blade more once engine starts. Do you have a fast idle setting?

When you say car stalls is that at fast idle in park/neutral and it just stalls after 25 sec. Or when you put it into drive and open throttle.

If this carb use to work fine, I would suspect stuck piston. if this is a new to you, maybe the thermostatic coil needs to be replaced. Carter had a different choke thermostat for almost every carb depending on engine/manufacturer.

The choke is opening to quick after start up (based on read the post) that's the housing adjust. A stuck piston will will run very rough from beginning the slowly clean up as the choke opens.

"A stuck piston will will run very rough from beginning the slowly clean up as the choke opens. [/quote]" That's exactly what happens if I set the choke butterfly just up to the housing, like instructions/video. If I leave a 1/16 gap with the butterfly and housing it starts..runs at a high idle and stalls when butterfly opens completely in less than 30 seconds. As the engine starts to clean up at cold start, the butterfly opens at the same time and a few seconds after the engine is "cleaned" up the car will stall (in park) because of loss of rpm. If I juice it when running, it will run but if letting off the throttle, it will stall until reasonably warmed up. This is a new carb..bought last Sept and had this issue since day 1.

Thanks again to all for the input

Yes but I don't think that is the issue fully Based on his statements. If he close the blade by richening the choke thermostat (more spring pressure on choke blade) his car doesn't like to start and sputters when it does. Either too rich, or pulloff not operating to slightly open choke blade.

I would check the piston, check fast idle speed and effect on choke.

It sounds to me like the choke setting is not done when the throttle is set on the fast idle cam. There may also not be a functioning choke pull off, or it is not opening the choke blade as much as it is suppose to. It also sounds like the fast idle speed screw may not be adjusted correctly.

It sounds to me like nearly all the adjustments are incorrect.

With the motor off and still cold, open the throttle about 1/2 way, and manually close the choke blade. This should lift the fast idle cam up so that when the throttle is released, the fast idle screw should be on the 2nd highest step (some are the highest step) of the fast idle cam. If it is not doing that, the rod to the fast idle cam needs to be adjusted so it is correct. There is a designed fast idle speed the fast idle screw is suppose to be set at (read the carb's directions).

With the throttle on the fast idle step, and the choke blade manually closed, the choke housing is rotated so there is enough tension on the choke blade to hold it closed. On a very cold motor, that tension could be pretty strong. There should be markings on the choke housing that rotates that identifies the "normal" choke tension setting, plus marks for a more lean choke or a more rich choke setting. Start with the setting at the normal position. Generally chokes function best below 60 outside degrees. All the choke adjustments have to be made on a cold motor. You can not properly adjust the choke if it is not cold, it will nearly always be set too lean and will open too fast

The Choke pull off should open the choke against the housing spring pressure about 3/16" to 1/4" (there is a drill bit index number for this setting between the choke blade and the top of the air horn. That adjustment is a starting point and the clearance is achieved by bending the linkage to the choke pull off). if it opens too much, the choke is too lean. If it doesn't open enough, the choke is too rich. Properly set, the motor should not run rich nor lean. The choke pull off has to be made while the motor is cold (if the choke pull off is vacuum operated, the pull off clearance can be done with a vacuum pump before the motor is even started). Once the motor warms up, the choke pull off adjustment has to wait for at least 8-10 hours.

'If I adjust the butterfly so it is closed,( just closed barely as the instructions say) the engine smokes and stutters until the choke opens up a bit."

This suggests the vacuum pull-off is either not attached to vacuum or the actuating piston is stuck. The car runs poorly until heat expands the choke spring enough to start opening the butterfly.

"If I leave the butterfly an 1/8 inch or so open..the motor starts and the choke works for about 15 seconds and then the car stalls. ( butterfly now almost completely open) Restart and it's like a cold motor with no choke and unless RPM's are kept up, it will stall."

Rotating the choke housing to open the butterfly 1/8 inch positions the butterfly for easy start, but it also reduces the amount of choke spring expansion required to open the butterfly the rest of the way. Once the engine is started, expansion of the spring opens the butterfly sooner.

Welcome to the world of automatic chokes:
Poorboy has pretty much covered the bases but I will add my

Make sure you have 12V to the choke. Many will try pulling power it off the coil which may only be seeing 8 or so volts.


What Many don't understand is there are several things interacting to get the choke functioning properly.
1. Preload on the butteryfly when cold,
2. Choke pull off adjustment
3. Butterfly position once started
4. Fast idle cam position
5. Fast idle adjustment
6. How long the choke stays on

If there are no markings on the housing use a sharpie or scribe to add one to the main choke body (botled to the carb) and a few evenly spaced both directions on the housing that rotates

A critical part of the process is in RED. if a motor has not run for more than a minute an 8 hour cold down may suffice. More than that, I'll make the adjustment I think it needs and leave them overnight.

Other items that come into play are a bumpy cam, loose mechanical advance that may make it hard to get a stable "fast idle" setting

The higher the fast idle is set the more the butterfly needs to be opened by the pull off. This is due to the engine needing more air or it will run rich.

if it is open too far the engine will stumble due to being to lean.

With the throttle open a 1/4 way or so The butterfly should close all the way with a light forefinger tension required to open it. When the finger is removed the Butterfly should close all the way with a light tension I want to say snap shut but lightly so.

With the butterfly closed, close the throttle. It should stop about .100 or a bit more from the hot idle screw

Open the butterfly so a 1/4' drill bit fits between it and the carb throat. (simulates the choke pull off opening the choke on a cold motor)

Open the throttle slightly to release the tension on the fast idle cam and release the throttle.

The throttle should now stop about .060 or more from the hot idle screw (if the fast idle is adjusted correctly.)

Are we having fun yet?

One thing to keep in mind: the choke preload only determines how long the choke takes too fully open. it is the other adjustments that determine the engines behavior when cold.

it can be frustrating if you do not understand how all of the above interact. Loose mechanical advance or a lumpy cam will aggravate the process but can be worked around with adjustments and tweaking

This is a trial and error process that may require several attempts to get it right. Every motor is a bit different unless stone stock. Even then they may require a bit of tweaking from the factory spec'd adjustments Once done they are wonderful. I love to fire my car up at a show have it run on a slight fast idle, blip the throttle and have it drop down a bit, put it in gear and drive out with no stumbling popping spitting etc.
hope this helps and keep us posted

Poorboy and TJP have it down pat. I spent a lot of years building/rebuilding/tweaking carbs. Living in WI we got real good at tweaking stat housing and choke pull-offs. One of the biggest reasons there is no choke on my toy...hop in, pump it a couple times and start it up. Feather the throttle for a few and good to go. I've fired mine up in Feb when the temps were WELL below freezing...took a bit more to keep it running but it fired right up! 470" with a Holley 800 DP.

Two shots from that double pumper helps with richening that mixture up LOL,
I see it as a challenge and love them When set up. My 38 ( 340 6 pak with mechanicals) can sit for a year. Key on, elect pump on, 2 or 3 pumps it'll start and die. two more pumps it starts and idles at about 1300, after30 seconds or so , blip the throttle, now at 1100 or so, drop it into gear and drive way
Had a 64 Dart years ago with a pretty radical 340 in it, no choke. Loved it when cold as it had a different even more radical sound to it especially when blipping the throttle to keep it running
I've always hated the cheesy aftermarket manual choke kits that cause more trouble than setting the automatic choke up IF one knows how they work. Most do not take the time to do so and blame the choke.
But this is true of most everything. When I taught classes on equipment I always told the students the first 2/3 of the class was the most important as we would break the machine down into subsections, Learn how each section functioned, then start reassembling to UNDERSTAND how they interacted with each other.
If one knows the above, the machine will just about diagnose itself by its symptoms.
Or one throws parts at it sometimes getting lucky and others creating more problems. In the second case they normally call it a POS and blame the item. Quadrajets, Carters, Edelbrocks, Holleys, Strombergs, and most others are all good carbs. They all do the same thing, but differently. One needs to know how they work before they can repair them. NOTE: I left Demon and Predator out purposely. the early Demons had some issues IMO, not sure about now.

I live in northern IL and I drive my stuff year around. Since I know how to properly set up automatic chokes, every carbed car I've ever owned, and drove on the streets, had a properly adjusted automatic choke. When they are properly set up, the motors run correctly from stone cold (-30 F) to dully hot (+90F). I can not understand how people can stand a poorly running car at any temp. Maintaining proper automatic chokes is just like maintaining anything else on a car. There are things you have do to keep functioning, but once set up, maintaining an automatic choke isn't any more difficult then maintaining any other part of a car.

Even my street drive high performance cars had operating automatic chokes. Our dirt track cars did not have a choke, but once those started up, it was past the need of a choke.