Choke Plate not functioning correctly

[JJHstang]

On my 71 Mach1 with 351 W it seems my Summit Racing 4bbl electric carb choke plate is not working correctly and my warm idle is to fast.
Just idling the car will get to approx. 12 mph and when stopped in park will not idle down.
The carb is not quite 3 years old. I am going by ear have no tach or vacuum gauge.
Attached some pictures of the choke plate at different stages.
Looking for suggestions.

 

[Threepointtwo]

I am far from a choke expert but I had a similar problem on my 302. It appears that the choke is not opening up all the way when warm and that may be the entire issue. There is a separate idle speed (higher) when the choke is closed and it should slow down once the car is warm and the choke opens up. I would start by clocking the choke to full open when warm. That is usually three small screws around the round spring housing. Just loosen them up and rotate the housing left or right until the choke plate is completely vertical. That might do it.

On my electric choke, as soon as the ignition is turned on, the spring starts heating up and opens the choke over a short period of time. This happens whether or not the car is running. Likewise, it takes a while for the spring to cool down after the key is shut off so the plate remains open for a while.

 

[JJHstang]

Thank you I hope that is it.
Should I warm it up , adjust while running or shutoff.

 

[Threepointtwo]

Thank you I hope that is it.
Should I warm it up , adjust while running or shutoff.

With the electric choke, you can do it without running. Just make sure to give the choke time to warm up fully.

 

[JJHstang]

Ok, saw one you tube that showed moving the choke open when cold while holding the throttle open. Then tightening the screws.

 

[JJHstang]

I loosened the 3 screws on the cap but can’t get the cap to move. What am I not understanding.

 

[Threepointtwo]

I'm not sure. This video has a pretty good explanation.
electric choke

 

[7991LXnSHO]

The screws hold a spring against the choke pull off, so they sometimes need to be loosened more than you think. Also, the choke pull off wedges into the carb body and needs wiggled or bumped loose. Pay attention to where the notch is before you knock it loose.

 

[JJHstang]

I'm not sure. This video has a pretty good explanation.
electric choke

Thank you for the video. I will need to loosen the screws more. I was never able to see the arrow on the choke cap.
I went and purchased a ohm meter to check voltage.
I need to get the choke working then adjust the idle. As mentioned before is to slow at startup, speeds up when warm and won’t idle down.

 

[JJHstang]

The screws hold a spring against the choke pull off, so they sometimes need to be loosened more than you think. Also, the choke pull off wedges into the carb body and needs wiggled or bumped loose. Pay attention to where the notch is before you knock it loose.

Thank you, mine never came loose enough to turn a and never see the arrow on the choke housing. I will loosen screws more.
Bought a ohm meter to check the voltage as well.

 

[7991LXnSHO]

Thank you, mine never came loose enough to turn a and never see the arrow on the choke housing. I will loosen screws more.
Bought a ohm meter to check the voltage as well.

I usually turn around the screwdriver and give it some light taps with the handle if I cannot pull or wiggle the choke coil loose. A rubber coated handle on a Stanley hammer would be safer, if not too heavy.

 

[JJHstang]

I usually turn around the screwdriver and give it some light taps with the handle if I cannot pull or wiggle the choke coil loose. A rubber coated handle on a Stanley hammer would be safer, if not too heavy.

Thanks

 

[JJHstang]

As I mentioned I bought the multimeter and hope I am doing something wrong. Sorry if this gets to long.
I have picture showing the multimeter with how I have it set. I tested on the battery and got a 12.7 reading which I understand is good. With the car switched on (radio worked) I disconnected the choke red wire grounded the black wire of the meter then touched the choke red wire clip with meter red wire no readings. I then connected the red choke wire back up and tried the meter the same way no reading.
Decided to start the car. The picture of the carb shows the plate open. That is how it is after car just stars and when warm plus idle stays high. If I manually push the red choke adjustment down a couple of notches the plate opens and idle lowers.
The other pics are just if the wiring.
I am hoping not using the meter correctly because not sure rewiring.

 

[Threepointtwo]

You should have 12 volts when you turn the ignition on. Can you trace your red wire back to the source?

 

[JJHstang]

I did and found where it is connected. I found if I moved the red wire I get a reading of around 10.7.
I opened the clip, took my pliers and squeezed to recrimp it. Tested and now get a reading of 11.88 which I figure should be good.
I tapped my gas pedal and plate shut. I now need to start it up and see how the plate opens.
I also loosened the 3 screws enough now to turn the choke cap then tightened back. If plate does not open enough I will adjust.

thank you.

 

[7991LXnSHO]

I would not be comfortable with the positive terminal uncovered so close to the negative terminal and fuel fumes on the side of the carb. An insulated female terminal end might not be required, but could be some help avoiding a spark. See pic. Color will vary by brand and wire gauge.
Detailed meter use basics and testing instructions are below.

That meter looks very familiar. It is very good for what you need to do and is not fragile. It should be helpful and easy to use. I have a second set of leads I extended for testing circuits and grounds, and you may want to do that for a future project.

Even if we do not know how many ohms of resistance the pull off should have, this meter can check for continuity. The ohm symbol is for the numbers in the left lower quadrant of the settings dial, and will measure resistance to electrical flow. The symbol to the right of 200 is a diode, and that can be used to check for continuity, aka if the component or circuit has a continuous path for electricity. Turn the knob there and touch the leads. The readout should go from no reading to (about) zero.

With the car off, remove the two terminals from the choke, and make sure the red (positive) one does not touch anything metal. (A piece of Duck tape or two layers of painters’ tape will temporarily protect it at only 12 volts.) Touch the leads to the two terminals and see if the reading changes. If it does not, the choke pull off is bad. It should be a number more than zero. (Without checking my Holley that’s in winter storage, I cannot give an exact number.)

Next check the ground side of the circuit. Plug only the black ground wire back in. Put one lead of the meter on the - terminal, and touch the other lead to the carb body. It should show zero. Then test between the - terminal and to a bare metal spot on the engine, then to the negative battery terminal. It should give you readings close to what touching the meter leads together does, so close to zero.

The continuity feature is useful for testing bulbs and other grounds. You appear to know how to test if something is getting full power.
I am surprised to not see a mark in the plastic on the choke pull off. If there is none on the Summit part, once you get it adjusted close, I’d use a sharp object to scribe a mark next to the middle of the scale. That way you can see how far you move it for fine tuning or to return it to the right spot after cleaning some time in the future.