choke / fast idle not engaging when cold

'87 pickup, 22R engine; carb has worked flawlessly throughout the years (except for one fix, described below). Last smog check I was told that it wouldn't make it next time, so I took it off to clean / rebuild it, thinking (like others) that it MUST be time to do so. After I took it off the manifold, it turned out that the dang thing was so clean that I didn't want to take it apart any further(if it ain't broke...), so I put it back on (sorry I took it off to begin with!) and adjusted the idle mixture (extreme adjustment, backed out four extra turns to fix the rich mixture problem, probably eroded fuel jets inside; the shop manual detailed the adjustment and I know I've got it right even though the needle is so far retracted) and the thing runs like a champ; the exhaust smells like breathable air again! after previously being so unbreathable. (I've also been running supreme in it since it was new, and I attribute a lot of the cleanliness to that. I know, people won't believe that, please don't harass me on the expensive fuel; I just like to take good care of my cars and feel it's worth it in the long run, and I don't know how else to explain a perfectly running carburator after 20 years with absolutely no varnish.) Anyway...

Now the cold idle / choke does not engage when the engine is cold. I actually had a similar problem several years ago when the choke butterfly valve was getting stuck in the throat, so I took off the butterfly and filed down the edge of the plate so that it would have clearance and it's worked well since then. The current problem seems to be coincident with me removing and reinstalling the carb (DANG!):banghead: so I'm sure I did something wrong on the reinstall. Fortunately, because I'm in California, I can usually start it every time, but when it's cold I have to manually keep the idle high for the first few minutes or it will be on the verge of stalling.

So I'm trying to figure out how the choke works. There is a wire coming from the choke bell housing and I don't know if the choke is electric or if that wire is an output to the computer. I'm guessing that there is either a bi-metallic coil in there, or it's an electric solenoid. (I had a '78 that had coolant running through it, and that was bad news when it rusted out.) In any case, when it's cold, there is not any force to close the butterfly or set the cold idle, and I've tried it with the ignition on too just in case the choke requires power.

That's all I can think of now. I know yung'ens aren't going to even know what a carburator is, but I'm hoping there are some out there who know about this. I read a previous post about replacing the carb with a Weber, and I would do that if I had a running problem, but this is relatively minor and I can't see changing it out at the moment; if I did, I would probably look into FI, but not going to do that presently, so let me see what you've got, motorheads! Thanks in advance for your help and responses.

~Dan

I recommend spraying the inside of the carb., both butterfly valves and throats and any thing else in there with Berrymans carb cleaning while the truck is running. I do this once or twice a year, ive got a 1988 with a carb and never had a carb problem. You will have to pull on the excellerator cable while spraying to raise RPM or it might stall. I first started spraying my carb about 12 years ago after my engine started pinging , so I sprayed a half can of Berrymans carb cleaner through it and it got rid of the ping and hasn't pinged since. I believe it got rid of the pinging by removing a lot of the carbon buildup on top of my pistons.

Thanks, Mike. I've sprayed my carb and linkages every year since the truck was new, and I agree, that helps and I didn't mention that in my original post. However, that is definitely not the solution to this problem. There is a lack of (spring?) force to even try to close the choke and set the fast idle when the engine is cold. There is either something missing (like a spring that fell off, unlikely in my opinion) or the choke mechanism has failed at some point. Thanks for the thoughts though.:popcorn:

Autoforum,

Sorry to bother you about your post, because it is so long ago. But what was the solution? I have an old '84 that has the same choke problem. was it a missing spring? or something like that?

thanks,
Steve

In case he/she doesn't respond, check the following:

The choke butterfly shaft may be binding or gummed up. Spray the choke and surrounding area with carburetor cleaner

Check the resistance of the choke heater from the terminal to the housing. Should be 20-22 ohms when cold.

Check the voltage to the choke heater when the ignition key is on. Should be 12 v to the heating element.

Check to make sure the idle-up diaphragm and choke opener are free to move.

Thanks Brian!
I continued to poke around on the internet and came across a pretty good write-up about the 22R carburator, could be handy to others. I will check mine as you suggest.
Steve

http://www.bluebassdesign.com/boonin/carb_faq/

I have an '85 FSM if you want it. Contact me by PM with your e-mail address.