Just some guy
Join Date: Jun 2001
Location: SC foothills, USA
With your engine dead cold (like from sitting overnight) your choke should be mostly open. When you stomp the throttle to the floor one time the choke should snap 90% shut. For testing you'll want to pull the air cleaner and then pull the throttle by hand so you can watch this happen. Then after the engine is started the choke tends to stay shut at first (and the engine should be idled up higher than usual) until the engine is revved a bit and then the choke plate will slowly begin to open and the high idle will pull off. Then the choke will continue to open very slowly as the engine fully warms up until it's fully open at almost straight up and down.
That's how it is supposed to work. A choke usually does one of three things. Sticks in whatever position because of heavy accumulated carburetor nastiness. Sticks shut because of a mechanical failure, bad adjustment, or electrical failure. Or sticks open because of bad adjustment or mechanical failure.
Plain sticking generally can be fixed with a good dose of carb cleaner spray and wiggling the linkage.
Stuck shut the car will start OK but will start idling choppily and likely just cut off as the engine warms up and can't get enough air. The car will behave as if it is "flooded" and may not start again until the engine cools back down quite a bit.
Stuck open means the car can be started but you have to pump the gas pedal a lot to keep it running until it warms up then it will behave normally. Unlike when the choke is stuck shut you can drive the car this way, it's just annoying to start cold. I have an old motorcycle I about never bother with using the choke and just start it like this regularly.
I stick with hooking the positive wire to the Stator post on the alternator just like Ford did on millions of vehicles they produced and have yet to see a good reason to make it more complicated by doing it differently as long you are using an original style alternator. I have seen people connect the choke to the same wire that provides power to the ignition coil. In warm weather they get by with it but when it gets cold the weaker spark makes the car hard to start. The choke "robs" power from the coil. Sort of. You can use relays and/or hook up the choke to different places, just NOT the coil wire.
The rear butterflies, or secondaries, should stay shut unless you are actually driving the car and getting on the throttle pretty hard. You generally won't get them to open when revving by hand in the garage. They should have zero effect on starting troubles unless they are stuck open somehow.
Last edited by GypsyR; 10-07-2012 at 10:24 PM.