258/Carter Hose Routing - JeepForum.com
 
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post #1 of 12 Old 05-03-2013, 12:57 PM Thread Starter
FallibleXJ
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258/Carter Hose Routing

Hey All,

My CJ has been running very rich recently, and I finally had had enough of it and wanted to see what I could do to fix it. I was told that vacuum leaks would be the likely culprit, so I decided to start there (carb was rebuilt a year or so ago). While looking through threads and website at pictures of where the lines are supposed to run, it almost looks like mine is backwards... can someone confirm this? The hoses Im concerned about are the two coming off of the valve cover. One is going to the air filter housing and the other into the base of the carb. All of the sites I looked at, the front one is for the PCV valve and runs to the base of the carb, the rear one goes into the air cleaner. Is there something wrong with mine being seemingly backwards?









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post #2 of 12 Old 05-03-2013, 01:08 PM
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post #3 of 12 Old 05-03-2013, 06:25 PM
86cj74.2L
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You should make sure your needle assembly is installed and set correctly. Its fairly easy.

Take the cover off the front top of carb and notice the round barrel with two needles. It's the center plastic arm.

Then back out your idle adjustment screw all the way Untill the throttle plates are completely closed and the screw isn't touching anymore.

Once this is done then loosen the screw on the shaft that operated the needle assembly and press down on it till it bottoms out. (You will be compressing a spring) then retighten the screw on the shaft. If you moved that arm any amount you just leaned out everything but idle and wide open throttle.

Then put your idle screw back where it was.

Also it would not hurt setting your fuel screws for lean best idle again. Make sure your idle is around 700rpm to do this. You don't want a high idle to set this.
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post #4 of 12 Old 05-04-2013, 06:29 AM Thread Starter
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Quote:
Originally Posted by 86cj74.2L View Post
You should make sure your needle assembly is installed and set correctly. Its fairly easy.

Take the cover off the front top of carb and notice the round barrel with two needles. It's the center plastic arm.

Then back out your idle adjustment screw all the way Untill the throttle plates are completely closed and the screw isn't touching anymore.

Once this is done then loosen the screw on the shaft that operated the needle assembly and press down on it till it bottoms out. (You will be compressing a spring) then retighten the screw on the shaft. If you moved that arm any amount you just leaned out everything but idle and wide open throttle.

Then put your idle screw back where it was.

Also it would not hurt setting your fuel screws for lean best idle again. Make sure your idle is around 700rpm to do this. You don't want a high idle to set this.
Any chance you could send me a photo of what needles you're referring to?
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post #5 of 12 Old 05-04-2013, 02:15 PM
86cj74.2L
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In this picture I have the cover removed and am pointing to the screw and arm that operate the needle assembly.
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post #6 of 12 Old 05-04-2013, 02:16 PM
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In this picture I'm pointing to the actual needle assembly. You can push down on the Allen screw area.
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post #7 of 12 Old 05-04-2013, 02:24 PM
INowUnderstand
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Someone correct me if I'm wrong, but if you have vacuum leak it is letting more air in and causing it to run lean instead of rich. I had some bad leaks recently and adjusting the idle mix screws out allowed the engine to at least run at idle. If you don't know take some time to learn the vacuum layout and difference between ported and manifold vacuum. Plenty of info to search here. For setups, Plus google adventures under the hood. Has a bunch of good info. taking pictures and asking questions good to. It really helps to understand all this

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post #8 of 12 Old 05-04-2013, 03:34 PM
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The carter BBD has its needle assembly inside a vacuum chamber ported to manifold vacuum. As long as proper vacuum is present the vacuum pulls on the barrel the needles are mounted to which compresses a spring and pulls the needles deeper into the main jets.

Loss of vacuum, be it from leaks, poor tuning, or simply getting on the gas will cause the springs to bush back on the needles which raises them around 3/16 inch higher richening up the part throttle fuel metering.

Edit. Holley and motorcraft carbs do the same thing but use a power valve.
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post #9 of 12 Old 05-04-2013, 04:23 PM
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ok, so I would guess a leak would make it rich to a point, more serve leak might cause it to start to lean back out?
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post #10 of 12 Old 05-05-2013, 12:06 PM Thread Starter
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Appears I have a Carter YF, not a BBD.
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post #11 of 12 Old 05-05-2013, 12:20 PM
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The YF operates on the same principle as the BBD. A leak will cause the needle to rise causing it to run rich.

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post #12 of 12 Old 05-05-2013, 03:03 PM Thread Starter
FallibleXJ
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Quote:
Originally Posted by John Strenk View Post
The YF operates on the same principle as the BBD. A leak will cause the needle to rise causing it to run rich.

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Okay thanks, I just got 'done' fixing the ghetto hoses for those two lines... Decided to swap the grommets while I was at it, one of which broke and fell into the valve cover... which added another hour to my project. But I'll see what it looks like tomorrow once its all set up. Thanks guys
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