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post #1 of (permalink) Old 10-12-2002, 11:47 PM Thread Starter
 
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How does this choke work?

I have a non-stock one barrell carter carb on my 90 yj 4.2L
It isn't an electric choke because there aren't any electric tabs to which I can hook up wires.It isn't a manual choke becuase there isn't anywhere I can put a cable onto.
I'm guessing its a thermal choke which I have heard about.I have no idea what they do though.
On the choke housing there is a metal tube that comes out.It looks to be threaded, and I don't recall how it was hooked up when I purchased the vehicle.It did have a cap on it, but it had a hole in it..but it looked like the hole might have come from heat.I've tried plugging it and running without anything on it, but it doesn't seem to work right.
The jeep dies all of the time for about the first few minutes.The first few weeks I had it, the jeep would start and run first crank and stay alive.
I would like to know what to do with this if anyone could help.


Thanks
Joey
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post #2 of (permalink) Old 10-13-2002, 01:14 AM
 
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Re: How does this choke work?

It COULD be a climatic control choke. I've played with them on a number of old Rochester Qudrajets in Chevy pickups. I don't recall a metal tube sticking out of them though. That argues that it is a vacuum choke.

If it is a climatic (thermal) choke, the hole shouldn't matter. There would be a metal coil inside that looks like the backside of one of those large termometers for the backyard. It uses heat off the mainfold to cause the coil to move, unloading the choke. You adjust this type of choke by losening the cap and turning it until your choke unloads at the desired temp.

I've not played much with chokes that use vacuum to unload them, so I can't say much about them. I've mostly played with climatic or electric or manual chokes. My GUESS would be that the vacuum line would have to be hooked up to a vacuum source that opens when the temp comes up and thus unloads the choke. The electric ones I'm familar with work this way, with an electric temp sender.

Let us know what you come up with!
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post #3 of (permalink) Old 10-13-2002, 02:29 AM Thread Starter
 
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Re: How does this choke work?

hmm does this help any?
This is the choke housing and a picture of that threaded tube
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post #4 of (permalink) Old 10-13-2002, 06:30 AM
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Re: How does this choke work?

[img]images/graemlins/smile.gif[/img] [img]images/graemlins/wink.gif[/img] [img]images/graemlins/crazy.gif[/img] Joey, Joey, Joey......you were born just thirty years too late! What you have there is a thermo-controlled choke. The threaded connection is for a piece of tubing to hook on. The tube is 1/4" and uses a regular compression tube nut. The tube goes to a spot on the exhaust (or on the intake where the exhaust crosses over) where it can sniff warm air and draw that air over the coil spring and OPEN the choke. So when everything is cold the choke plate is CLOSED, and will open when it sniffs enough hot air. USUALLY there is a LOOP of tubing that goes from the clean side of the air cleaner....past the hot spot where ever they found one....and then to the choke body. The reason for the loop is because the carb pulls air into the choke body and if it isn't clean, crud and dust will eventually plug up the tiny vacuum passage that draws the air into the choke body. [img]images/graemlins/cool.gif[/img] [img]images/graemlins/smile.gif[/img] [img]images/graemlins/crazy.gif[/img] [img]images/graemlins/tongue.gif[/img] Pretty cool huh? [img]images/graemlins/cool.gif[/img]
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post #5 of (permalink) Old 10-13-2002, 08:48 AM
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Re: How does this choke work?

Joey (and other youngin's), this isn't a slam, just an observation on my increasing age (and I'm only 35!).

I am running into an increasing number of people who have never seen things like the thermo-choke you describe. Other things on the list are "three on the tree" and the need for "double clutching" an old "non synchro trans". Also the seemingly large number of people who, when you tell them you can rebuild and tune a carb, they look at you in amazement that you know about those old contraptions and they think EFI is a much easier system to work on.

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post #6 of (permalink) Old 10-13-2002, 10:10 AM Thread Starter
 
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Re: How does this choke work?

thanks
so this is obviously an old carb then :P
I'm assuming my engine won't have any provisions to hook it up then?
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post #7 of (permalink) Old 10-13-2002, 10:33 AM
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Re: How does this choke work?

</font><blockquote><font class="small">In reply to:</font><hr />
they look at you in amazement that you know about those old contraptions and they think EFI is a much easier system to work on.

[/ QUOTE ]

God im only 28 and i feel that way. HEHEHE

Joey im not 100 percent sure but i would have to guess that your jeep came factory with an eletric choke. It may just be easier to use a electric choke on that carb. It should just bolt up. I believe the wire comes from the oil switch.

If i am wrong here. Someone correct me. I havent messed with a 258 in awhile now.
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post #8 of (permalink) Old 10-13-2002, 11:43 AM
 
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Re: How does this choke work?

My 1980 amc cherokee had the thermo exhaust tube thing on it, its still on my factorey 2bbl manifold.

if you cant find where to hook up the thermno tube, run a heater hose right next to the choke housing, and use zip ties on each side, old FORDS used a choke setup just like that.

youll want it adjusted a bit lean so itll pull off quicker with the reduced heat

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post #9 of (permalink) Old 10-13-2002, 07:18 PM
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Re: How does this choke work?

[img]images/graemlins/crazy.gif[/img] Mr. Lem N. Squezins, chief mechanic and owner of Lem's Repair on Mophandle Road down in Dismal, Tennessee says that you can just use a piece of tube and wrap that sucker once around the nearest exhaust port so the tube gets hot. He uses a Bull Durham tobacco sack for a filter on the end of the tube. Claims it works perfect! [img]images/graemlins/tongue.gif[/img] Speaking of old.....I have a John Deere tractor that is fifty years old, and I can remember as a kid wishing we had one of those "new" John Deeres when this model came out. [img]images/graemlins/crazy.gif[/img] [img]images/graemlins/shocked.gif[/img] I STILL remember this kid in my class crowing about his family buying a BRAND NEW '53 Ford. We thought that Ford was the absolute LAST WORD in ground transportation! How could you possibly improve on what was obviously perfection. [img]images/graemlins/laugh.gif[/img]
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