Any Electric Choke Guru's?

I'm gonna come right out of the box saying I know nothing about them. Well maybe a vague idea but not much. What does it take to make one work properly? I may be missing something ? I am not able to get it to set right, I have checked the linkage and sitting there cold I can get it to the high idle lobe on the cam/carb. Is there supposed to be a temp sensor or something in-line with the choke circuit ? I have it wired direct to key , I have the idea that isn't right, not sure. I need an Electric Choke 101. All of my Motors and Chiltons seem to bypass any good info on this.
Thanks, Joe

This is an Edelbrock/carter type 4bbl carb

There is a flat coil spring under the black plastic cap on the choke mechanism. One end of the spring is anchored to the plastic cap and the other end of the spring is attached to the choke shaft. The cap can thus be rotated to open or close the choke. The spring is a special material called 'bi-metal'. It is made of two metal alloys that are bonded to each other and have widely different thermal expansion values. All metals expand when they are heated and these two metals expand at different rates so as the spring gets hot, it tends to unwind as one surface gets longer than the other. When the spring cools, it winds back. If controlled, this winding and unwinding could be used to rotate a shaft as in a carburetor choke. This is exactly how your automatic choke is working. The 12V wire you connected to the choke heats a resistance heater that is enclosed in the choke housing next to the bi-metal spring. When you turn your key to 'RUN', the resistance heater begins to warm the spring and the choke slowly opens. You can adjust the opening time by turning the cap and loading or unloading the spring closing force on the choke.


kgdb

Most choke systems will also have a "pull off" of some sort, usually operated by vacuum...ie you set the choke to close while the engine is cold and then immediately upon starting the vacuum pull off circuit will crack the choke open appx 1/8- 1/4" so it can get enough air to run, otherwise it will sit there and "load up" or run rich and you have to keep giving it more throttle to create enough vacuum for the engine to keep running and not flood out...

Some pull offs are external mounted vacuum "motors" or "dashpots" that you can see..others, I recently found on my carter rbd is an internal vacuum circuit, (mine was plugged full of carbon gunk).

Its kinda of a tricky set up, but its beautiful when it works,...well, not as beautiful as fuel injection, but it is what it is..

If you have an older non electric choke they usually pull heat off the exhaust manifold in order to help the spring to heat up..

One way or another the spring has to be heated, electrically or radiantly/vacuum assisted.

What kind of symptoms are you having with yours?

Everything has to be working together , kind of like musicians in a band, for it all to work properly...if one component..spring, electric element, vacuum line, wire, heater tube, etc...gets broken, worn or whatever it will either flood or hesitate and sputter and die when its cold..

Thanks guys ! What I have is the simple electric bi-metal set up, So right now I am thinking I am not loading the coil enough and its kicking off to quickly. Magic , I am just having hard starting issues with this colder weather, it hasnt worked well since I fired up the engine but I have lived with it because I hadnt been trying to run in these cooler temps . I can assume it's a trial and error thing on getting the tension set right then ? As it is, It is just putting enough pressure on the choke to close it when cold, probably not enough to hold it and keep it on fast idle. The fast idle screw was backed way out so it was never used I guess, I bought this carb used, but other than that it works great.

not an expert, but i set them buy rotating cap until it just barely closes (set when cold) gets it close. fine tune every morning with very slight amount until happy. all the ones i had have 3 screws and a metal ring holding the cap in place, just loosen screws a turn or 2. dont forget to retighten. by the way, mines not hooked up.

I have adjusted thousands of these in climates 0 to -40 .
There is beasicaly about 5 adjustments all of which will effect each other when any one is changed.
I will speak in general terms.

#1 Your power wire should be to the alternator output or another source that is powered when the engine is running (not key on engine not running). some electric choke wires are conected through a resistance wire or resistor so they don't come off too fast or burn up from being on all the time.

#2 there should be an index range marked on the plastic cover mating a notch on the alluminum housing. set it about two notches ritch to begine with. realise that as you tighten this choke spring you make it need more "pull off", more fast idle screw and it will stay on longer.

Note: The choke system can only be tested after the engine has been off for 8 hours minnimum "cold" . when you start the engine cold you have onlyt\ seconds to observe it. five to ten seconds of running and its too late to get a real picture of its opperation. After that obsevation you have to make a calculated adjustment and then try again the next day. it usually takes me three trys (three days) before I get a very screwed up choke back to where it should be.

#4 when cold and you step on the accelerator to relieve the linkage on a cold engine the choke plate should spring closed and the fast idle adjustment screw should be just on the edge of the highest step of the fast idle cam. If not there is a specific place on the linkage rod to bend it for adjustment.

#5 when the engine is first started there should be a "choke pull of " as Magic Bus said. it is a vac opperated motor that will pull the choke plate open about 3/32" to 1/4" or so assisted by the influence of air movment at fast idle speed. IF not enough the engine will run slow and probobly chug and give black smoke and then slowly speed up within a minute. If too much the engine will speed up fast and maybe stall or stall if put in gear or trying to drive away.
At the same time during the first few seconds of running if the pull off is right the fast Idle cam should also drop to the second highest step on the cam and the fast idle scrw should alow a speed of about 1000 to 1200 rpm. If you have an external vacuum pull off you can hook a hand vac pump up when it is cold and see how much it opens the choke and where the fast idle cam gets to without turning on the engine or key. This is of great bennefit for doing the initial adjustments. Your carb may have an internal pull off motor, can you tell by looking at it?

#6 within 3.5 to 4 minutes the choke should be completly off and open and down to crb idle speed of around 650 rpm. during that 3 minutes the choke plate and fst idle cam should progresivly move open and to lower cam levels until off completly. you have to keep just touchiong the trotle to observe this.


does youe intake manifold have a heat riser exhaust passage under the carb? If so did you install the intake?

Discribe the problem exactly as it happens for the first 3.5 minutues of running from a "cold" start. and I can probobly tell you what to adjust.
I am presuming the choke linkage has not been all tampered with since the last carb overhaul? since the history of this carb is unkown and you are saying the fst idle screw is backed right off it probobly has been all messed up.

Lets start with a desription of exactly what it does.


M1D

This is what I am running, carter AFB on a Torker2 intake.

For some reason I have almost no decent pics of the carb installed on engine.
I have run the fast idle screw in to engage and idle at a what seems to be okay RPM . I will play with the choke coil some more in regards to the indexing on the cover. Is there a pull off missing on this then? I got to thinking about it and to be honest I haven't messed with one of these Carter 4bbl carbs in nearly 30 years ! And that ran a manual choke. All my vehichles since then have been quadrajets and TBI or newer.

It will be good to see a picture of the choke side.
And get a picture of the carb exploded view . Search the carb # and find a picture. The electric choke stat may be an add on if the carb originally had the pull off built in.
Normally the built in pul off is used with a choke stat that needed the hot air tube from the exhaust passage directly under the carb.
Or maybe the pull off was externat and is missing?

either way you can make it work but we need to know more about the carb model.

Do you remember when you installed the intake if the gasket was open, closed or restricted.?

M1D

I can't recall on the intake gasket, it was just a basic overhaul kit from the parts store, But Im pretty sure there wasnt a passage in the intake for that, amazing what you can forget in 2 years. I'll have to have a chance to flip the DH to do a number search.



Still looking for an exploded view. Right now I think I have the choke tension cutback to zilch.

I just found this , seems like an AFB Bible
http://www.raylinrestoration.com/TechnicalPages/Carburetors/AFB%20Tuning.pdf

those carbs are now known under the edelbrock banner. used since the 60's on everything from gm to dodge. originally sold as A.F.B carbs. we knew them as " all for backfiring". the best power supply for the choke is to use a switch from the engines oil pressure to send the 12v supply. that way you can leave the key on and no power goes to the heating element in the choke.
as for my best guess at the adjustment wind the spring till the choke plate just closes and add two more lines on the housing.

That is agood article and describes much.
Like JKR said, a three wire oil presure switch is one good system for the 123 volt connection but there are also other choices that do not provide 12v until the engine is running.

The carb does have the internal vacuum pull off. I can see in the article that the casting has the provision for the little piston I discribed at the bottom of the choke housing. You may need to remove the choke stat to verify that is working.

I can see in the picture that the choke stat index mark is way lean outside the marks on the alluminum casting. Maybe thats all you need do is bring it up to the marks. I would do that first of all and try it the next day.

One other choke function I forgat to mention is the "clear flood" mod or "unloader" . When you push the pedal right to the floor a lever should open the choke plate right up.

M1D

I reset the marks to 2 notches rich ,, it unloads ok after about 2-3 minutes, I have to play with it some more to see if I can get the choke/idle to set right with the throttle, I cant seem to get it to set the high idle cam right, might have some issues there, and of course its warm enough now I dont really need it,,lol , but the 3 wire switch sounds like a good way for my system, and I will see what I can come up with on that.
Thanks guys