Carter automatic choke

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Dion
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Carter automatic choke

Post by Dion »

The (automatic) choke mechanism in my car is not working. It is a Oct 1968 Interceptor 383 with, I think, the original Carter carburettor.
The small pin that goes to the chamber underneath the carb is very loose and does not move automatically. I can move it up and down manually, it then moves the choke flap. It should move I think according to the temp in the chamber? What would be fitted to the end of the pin in the chamber?

When I manually close the choke flap, the engine still will not start. It only starts when spraying starter fluid directly in the carb. After starting, it runs very well but from cold it always needs some starting fluid sprayed in. Am I correct in thinking the choke mechanism should also spray extra fuel when starting? Which obviously does not work now.

Any tips what might be wrong or missing? Or any tips where to find more information about the details and working of this carb? I do have the 1971 Mopar manual but it does not cover this carburettor.
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slotcarone
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Re: Carter automatic choke

Post by slotcarone »

The choke does not spray any extra gas into the engine. You have to usually pump the gas at least two times when cold starting and that will spray extra gas into the engine to get it started. It should then run at high idle on the choke until you touch the gas pedal and allow it to idle down. :)
1972 Interceptor III
133-5612
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Per
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Location: Norway

Re: Carter automatic choke

Post by Per »

After a hot'ish run the fuel will evaporate from the bowl. So cranking first and then a couple of stomps to make the accel pump spray fuel into the carb. Then churn away. BTW I finally gave up on the mechanical pump for this reason and replaced it with an electrical one when the mech pump failed.
Per
Not only English cars these days, an Italian is part of the stable again 8)
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Kevin Birch
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Re: Carter automatic choke

Post by Kevin Birch »

The choke opens and closes the flap at the front of the carb, and is operated by the linkage you have pointed to. When cold the flap should be closed, and by depressing the throttle pedal, before starting, closes the flap and squirts a small amount of fuel into the chambers via the accelerator pump. The choke doesn't spray fuel, it closes the flap to enrich the air fuel mixture. As the engine heats up a bi-metalic coil connected to the other end of the rod( disappearing into the inlet manifold) pulls the rod down, and opens the choke flap until it is fully open.
You need to remove the carb to access the bi-metallic coil, (undo 4 bolts, fuel line and disconnect the choke rod and throttle cable from the carb), and there is a cover held on with 1 nut, under which is the coil. If you take it out and heat it up with a propane torch or heat gun it should move, if it doesn't then it may be seized or catching on the the little frame that surrounds it, so give it a good clean and a coat of copper grease. Check it hasn't been assembled wrong, it is possible to put the coil back in the little frame so that it pushes up when it gets hot, rather than pulls it down. If it doesn't move after being cleaned then a new one will need to be bought.
You also need to check your accelerator pump, which is on the front corner of the LH side of the carb. There is a linkage to it which pushes it down when the the throttle pedal is pressed. There are three holes in the top part of it, and the rod from the throttle linkage should be in the middle one. To check it is working, after starting it to ensure there is fuel in the float chambers, switch the engine off, pull the throttle cable back and see if the accelerator pump is actually operating,it should be pushed down into the carb. If it doesn't move, then is it disconnected or is it seized, try manually pushing it down.If it does move down, look down the front venturiis and see if any fuel is squirted into them, if so the pump is working, and your problem is the choke causing difficult cold starting. If no fuel is seen then the seal has gone south on the accelerator pump, and will need replacing. If it has, it would be best to send the carb to Dave Barnett for a full rebuild, as other parts will be past their best too.
This sounds a bit long winded but actually only takes a few minutes to check the pump, and the carb will come off in 10 -15 minutes or so. If you do take the carb off, just ensure nothing falls into the inlet manifold, by covering it.
To remove the throttle cable, just undo the knurled nut on the very end of the connector, which will release the metal bulb from within. When doing it back up, ensure it is not too tight, and the bulb can freely move , a little grease on it will keep it smoothly operating.

Good luck.
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slotcarone
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Joined: Sun Aug 29, 2010 1:38 pm

Re: Carter automatic choke

Post by slotcarone »

Dion if your carb is working correctly unless it is very cold outside you should not need the choke to start the car. If you pump the gas 3 times and hold the pedal down a small amount it should startup even without the choke. You will of course have to keep your foot on the pedal for a short time until the engine warms up a little. When you say the choke is not working do you mean when the car is cold and you step on the gas the choke butterfly does not move? :)
1972 Interceptor III
133-5612
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