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Old 06-07-2012, 06:14 PM   #1
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Getting to know whats under my hood

Have all fuel injected cars, except my Buick and it has no emissions and is not nearly as fickle as the jeep. I am trying to learn everything under the hood so I can tune her up. That being said, here are a couple pics and questions.
Are these the mixture screws I use to adjust the carb?

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Old 06-07-2012, 06:15 PM   #2
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What are these babies attached to the air cleaner housing? Emissions no doubt

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Old 06-07-2012, 06:17 PM   #3
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Is this how I adjust the lean rich mixture? If so, how do you tell where it is set? I now you loosen three screws to turn it
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Old 06-07-2012, 06:28 PM   #4
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The last pic looks like an electric choke.
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Old 06-07-2012, 07:28 PM   #5
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Is this how I adjust the lean rich mixture? If so, how do you tell where it is set? I now you loosen three screws to turn it
For the auto choke. I have mine set at 1 notch rich. That works the best for my 4.2.
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Old 06-07-2012, 07:29 PM   #6
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What are these babies attached to the air cleaner housing? Emissions no doubt
You're right. Don't touch them.
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Old 06-07-2012, 07:31 PM   #7
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Have all fuel injected cars, except my Buick and it has no emissions and is not nearly as fickle as the jeep. I am trying to learn everything under the hood so I can tune her up. That being said, here are a couple pics and questions.
Are these the mixture screws I use to adjust the carb?
If it's the carb. I think it is, no. Just internal. There should be external mixture screws. May or may not be capped.
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Old 06-07-2012, 08:00 PM   #8
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For the auto choke. I have mine set at 1 notch rich. That works the best for my 4.2.
How do I tell what it is set on now and how do I adjust it to 1 rich?
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Old 06-07-2012, 09:02 PM   #9
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How do I tell what it is set on now and how do I adjust it to 1 rich?
Your photo shows that it's set on the "index" mark. The black housing should be marked "rich" and "lean". If the graphics are worn, then based on your photo I would move it over clockwise 1 "notch" or mark. It's pretty much hit or miss on these old carbs. because the internal auto choke springs are sometimes worn. If you adjust it and it runs better cold on the high idle then it's fine. You can always move it 1 or even 2 notches rich or lean as needed. I wouldn't go more than that. You basically have to experiment a bit until you get it the way you want it. Sometimes the index mark is best. I would only move it if there's a problem. For example, running a bit rough on a cold start. You only make the adjustment and any re-adjustments on a cold engine. Of course you can set the auto choke with a warm or hot engine but you'll only be able to tell if the adjustment has worked when you start it cold (sitting overnight is the best).
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Old 06-07-2012, 10:01 PM   #10
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Your photo shows that it's set on the "index" mark. The black housing should be marked "rich" and "lean". If the graphics are worn, then based on your photo I would move it over clockwise 1 "notch" or mark. It's pretty much hit or miss on these old carbs. because the internal auto choke springs are sometimes worn. If you adjust it and it runs better cold on the high idle then it's fine. You can always move it 1 or even 2 notches rich or lean as needed. I wouldn't go more than that. You basically have to experiment a bit until you get it the way you want it. Sometimes the index mark is best. I would only move it if there's a problem. For example, running a bit rough on a cold start. You only make the adjustment and any re-adjustments on a cold engine. Of course you can set the auto choke with a warm or hot engine but you'll only be able to tell if the adjustment has worked when you start it cold (sitting overnight is the best).
Thanks. I have read "about" setting but never how to. It starts cold fine. It is the starting after it has warmed up and then driving for a while, parking, then trying to restart that takes a while. Maybe 6 seconds of cranking, sometime alot more.
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Old 06-07-2012, 11:10 PM   #11
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When you go to start it hot try pushing the gas peddle about 1/3 way down and hold it there and see if it starts faster.
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Old 06-08-2012, 06:34 AM   #12
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When you go to start it hot try pushing the gas peddle about 1/3 way down and hold it there and see if it starts faster.
I have tried that. I noticed the other day that my high idle screw was missing. This, I believe, was not allowing my choke to open up all the way and causing it to run a bit rich. A member on here was kind enough to mail me a new screw, which I installed last night. I am hoping when I drive it today the problem will be rectified. Also, is it true that you must turn the key to the "on", not "start", position before pressing down on the gas pedal?
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Old 06-08-2012, 07:41 AM   #13
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When you go to start it hot try pushing the gas peddle about 1/3 way down and hold it there and see if it starts faster.
This. On a warm or hot engine with a carb'd 4.2 this is the best way to start it in order to eliminate excessive cranking. It even indicates this in the old manual.
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Old 06-08-2012, 07:56 AM   #14
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I have tried that. I noticed the other day that my high idle screw was missing. This, I believe, was not allowing my choke to open up all the way and causing it to run a bit rich. A member on here was kind enough to mail me a new screw, which I installed last night. I am hoping when I drive it today the problem will be rectified. Also, is it true that you must turn the key to the "on", not "start", position before pressing down on the gas pedal?
I hope it works for you but I don't think the high idle screw will affect it hot. It's not true that you need to turn the key to on before setting the choke or pressing the pedal. As a matter of course when I start my vehicles I briefly pause at the on position and then start, F.I. and carb'd. It's not required. It's just something I was taught too many years ago by an old tech that worked on the original F.I. Corvettes. His rational was basically that you don't "shock" the system by giving the pumps/servos or whatever a split second to activate before the engine is then started. Could be an old wives tale sort of speak and before that I never had a problem. How I start doesn't hurt anything so that's what I do. One thing I would do is clean that carb in and out real good with it running with carb and choke cleaner.
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Old 06-08-2012, 08:22 AM   #15
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Do you spray the carb cleaner into the carb with it running?
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Old 06-08-2012, 11:30 AM   #16
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Do you spray the carb cleaner into the carb with it running?
Yes. While you're doing it give it throttle from the carb so it doesn't stall. Spray everything in there completely. Everything in and out, linkage, etc. The can will have a tube so you can get in there. Carb & choke cleaner won't hurt it. Just be careful of the fan & belts. An added benefit is that while you're spraying the exterior of the carb if you find that it starts to bog down a bit that means you have a vacuum leak.
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Old 06-08-2012, 03:28 PM   #17
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...... It starts cold fine.....
You dont need to touch that choke setting, its fine.

Those screws are not your mixture adjustment screws, dont touch them, the mixture adjustment screws will be on the otside in the lower area that the butterfly shaft goes through:


source:
Moses Ludel's 4WD Mechanix Magazine - Rebuilding the YJ Wrangler 4.2L BBD Carburetor

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Yes. While you're doing it give it throttle from the carb so it doesn't stall. Spray everything in there completely. Everything in and out, linkage, etc. The can will have a tube so you can get in there. Carb & choke cleaner won't hurt it. Just be careful of the fan & belts. An added benefit is that while you're spraying the exterior of the carb if you find that it starts to bog down a bit that means you have a vacuum leak.


Dont make this a habbit, if your engine backfires through the carb, you end up with a fire, burnt Jeeps are not any fun....

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