Electric choke keeps re-engaging

[cwest]

86 K20.  Not sure if this goes here but my choke has now started to re-engage whenever I give the truck a little gas to accelerate.  It still warms up from a cold start normally, and shuts off when I goose the gas like it always has.  However now when I accelerate from a stand still it re-engages and begins to rev the engine.  It works as a pseudo cruise control at 35MPH , but it makes stopping a bit more precarious, which is always key.  Does this sound like my choke just went bad, or something more in depth?   

[roundhouse]

You checked to see if you have power to the wire on the choke ?

And that the electric element heats up ?


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[Kren420]

Throttle return spring? Mine got to the point where I goosed the gas, the throttle would close and work fine.  But when I gave it a little gas it would just not quite close all the way, giving me a kinda cruise control lol.  New spring fixed it right up.

[mcintyrederek]

The fast idle cam needs to be cleaned and lubricated.  You also have a vacuum pull-off on that side of the carb.  The electric choke thermal spring should have 12 volts on it when the ignition is on.  Some people use B+ from the distributor as long as there isn't a resistor in line to drop the voltage..  But you probably have all that working.  When the ignition is off, the spring in the electric choke coil cools off and fully closes the choke plate.  It also resets the fast idle cam, which will remain on fast idle until the next time you press the gas pedal, even a little bit - then the cam drops out and the main idle screw (right side of carb) will determine your idle speed.

The choke will be fully closed when the vehicle is COLD, ie, sitting for a few hours at most.. Naturally the engine won't run at all with the choke fully closed, so just as soon as you hit the starter and the engine fires, vacuum is pulled on a pull-off vacuum diaphragm and it allows the choke to open just a little bit, just enough for the motor to run.  As the electric choke warms up with the 12 volts on it, it gradually opens the choke and keeps it open fully after a few minutes.

Your problem doesn't sound like it's in the electric choke.  It sounds like the fast idle cam isn't releasing or it's sticking.  Clean all moving cams, springs, etc, with choke cleaner then spray some mild lubricant on it and see if that helps.

Just to be hypocritical, I took my auto choke and fast idle cam off because I got irritated at it, and put a manual choke on it.  Works great, but I wish I hadn't done that now that I think back on it, with a little patience, I could have repaired it like it was supposed to be.

Good luck.

[Stewart G Griffin]

Do you visually see the choke start to close up when you accelerate?

[cwest]

Thanks for the good responses, Gents.  The return spring idea sounds like it might be the quickest fix, I already got the spring so just need to put it in.  I'll throw some lube around the levers and whatnot and see if that works first.  If that doesn't do it.. Looks like I'll be researching how to work on the fast idle cam.  I'll report back my progress.

[Stewart G Griffin]

If everythings adjusted properly it should switch down to mid-step as soon as you tap the throttle even if you just started the engine.

[cwest]

Throttle return spring is the winner!  I bought a pack that had four different springs (one of which being the exact match).  After replacement it worked a little better but still didn't bring the throttle all the way back to idle, so I used another spring out of the pack that had a little more tension, this ended up being the ticket.  That whole mechanism is a little gunked up so I think it needs a little extra umph to pull it all the way back, I'll shoot it with some brake cleaner one of these days.  Thanks for the good replies, gents!