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post #1 of (permalink) Old 10-05-1999, 10:01 AM
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Several tech questions

I took out my Carter BBD to do the idle tube cleanout, and turned it upside down to scrape off the old gasket. Now, when cold starting, it starts immediately, but then sputters and dies within 10 seconds and is very hard to start after that. When it is warm, it cranks first try and it purrs beautifully. Could I have dislodged or dropped something out of the carb when I uprighted it or does this sound like a choke or timing problem (both of which I adjusted - perhaps incorrectly)? Could a bad cat converter be the cause? I took the plugs out and cleaned them and I also did the Nutter thinking the computer was the culprit, but it had no effect on the problem. I also have sooty deposits in my air cleaner indicating a bad pulse air check valve. Would this contribute to the problem? Sorry about the long post. I'm so confuuuusseeddd!!!!!

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post #2 of (permalink) Old 10-05-1999, 11:37 AM
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Re: Several tech questions

There are a couple things that could of been dislodged, one thing I can think of is a float or needle. I'd watch the flow of fuel when
it starts and see if it gushes out, a float might be jammed.

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Terry L. Howe http://www.off-road.com/~txh3202
post #3 of (permalink) Old 10-05-1999, 09:00 PM
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Re: Several tech questions

First of all, take care of the A.I.R. check valve first, or you will probably end up cleaning out the emuslion tubes again. You can plug it or cap it off until you get around to picking up the new part. Also if you are getting exhaust into the air cleaner, the vacuum switching valves on top of the A.I.R. check valves are probably bad also. They can be tested with a hand held vacuum pump.
Next, there is more than one adjustment to a choke. The spring tension is probably the most least likely to fail, and the most adjusted part of the system. The choke pull-off, or vacuum brake, is probably the cause of your problem. When you hit the throttle the first time, when cold, it sets both the choke plate totally closed, and brings your throttle up on high idle. The moment you start the motor, your choke brake, or pull-off, uses engine vacuum to open the choke plate to a specified clearance. It does this to prevent flooding. This adjustmint is very critical, and is also matched to the choke idle speed adjustment. This adjustment is done by bending the rod from the pull-off to shorten or lengthen it. Usually the vacuum diaphram on the pull-off just fails, and by simply screwing on a new one, without modifing the rod length, will fix the problem. Another overlooked adjustment is the choke unloader. This is the mechanicial foot on the throttle shaft that opens the choke plate to a much larger clearance, in the case of extreame flooding. If the engine won't start cold, there is no vacuum to open the choke brake, so this device is used to clear a flooded motor. Another thing to keep in mind is it the throttle linkage won't open the throttle plates completely, the choke unloader won't work. Checking your linkage for proper wide open throttle, will give both tremendous horsepower, and better cold starting.



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post #4 of (permalink) Old 10-05-1999, 09:28 PM
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Re: Several tech questions

It seems like you know what your are talking about. Here's a different question. Forgetting emissions and emission laws, if a carb like the one being discussed here were to be replumbed for a hand operaterated choke like in the old days and all these vacuums, rods that have to be bent, springs, A.I.R. thing and all the rest of that stuff be junked, could this solve all these problems and make a real simple setup? Not planning anything like this myself - I have a fuel injection - but am just curious. A hand choke used to be real easy to use. Can it be done again? Now, how about legally?
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Doug '97 TJ
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post #5 of (permalink) Old 10-05-1999, 10:13 PM
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Re: Several tech questions

I installed a manual choke on my 84CJ, BBD carb and it worked just great. To set the choke, you'd have to step on the gas, pull out the lever, and start it up. Gradually over 10 minutes I'd push the lever back in to open the choke and step down the idle. The only problem I had is when someone else went to drive it, I'd have to explain in length how to use it and I couldn't quite get the message across that you couldn't just yank out the lever without stepping on the gas pedal first. Then someone would forget and it would be roaring at 1500 rpm warm idle. So when I installed a rebuilt carb I went back to the auto choke. Emissions considerations weren't a problem for me since there are no emissions testing in WY, but I don't think there would be much of a problem since testing is done with a well warmed up engine, right?

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