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Unread 12-15-2013, 07:04 PM   #1
kirbot
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1981 CJ7 
 
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Tuned the carb, now it won't idle!

I've been wracking my brain over this, and it isn't helping....

I've got a 1981 CJ7 with the 258 (actually the engine is an 83, if it makes a difference...)

It has the stock electronic ignition with newer ignition module, and a Motorcraft 2100 carb.

Here's what I've done recently...
I added a fuel return line to the tank, cleaned up the contacts in the distributor cap, leaned out the carb some, and set the timing.
And now, suddenly it just wants to stall at idle. It seems ok when it's revving, but as soon as you take your foot off the gas, it stumbles and wants to die.

I adjusted the carb back to where it was, moved the timing all over the place, and I still can't even get to idle again. Holding the choke closed (even when it's warm) seems to help some, but it's still not perfect.


Any ideas? My only other idea is to take the carb apart to see if anything's clogged up.

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Unread 12-15-2013, 08:46 PM   #2
Matt1981CJ7
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Sounds like carb rebuild time to me.

New fuel filter? Did you check fuel pressure?

Matt
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Unread 12-15-2013, 09:52 PM   #3
kirbot
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Quote:
Originally Posted by Matt1981CJ7 View Post
Sounds like carb rebuild time to me.

New fuel filter? Did you check fuel pressure?

Matt
I only put the 2100 on about a year ago, and it was rebuilt then. Maybe something made it through the filter and crudded it up.

It is a new filter, I used one with two outlets, one running back to the tank.
I haven't checked the fuel pressure, but since it runs fine once you step on the gas I didn't think that could be a problem.


The Jeep has always stumbled and stuttered if I hit the gas too fast. That's what started me messing with adjusting the carb and the timing,
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Unread 12-15-2013, 10:56 PM   #4
CoryA
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It idled before you made these changes? If so I wouldn't jump to a carb rebuild because I don't think it would fix your immediate problem. I would check the fuel pressure as Matt said
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Unread 12-15-2013, 11:49 PM   #5
86cj74.2L
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If it always stumbled and studdered since installing it search the Fourm on what others are using for their main jets and power valve and see what's in yours.
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Unread 12-16-2013, 04:29 PM   #6
scrapman
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How did you "lean the carb out"? Did you use a vacuum gauge and set both idle screw the same to get the highest idle vacuum? Did you have any backfires through the carb when you were adjusting the timing? If so, you could have blown the power valve, which is allowing too much fuel at idle.
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Unread 12-16-2013, 04:52 PM   #7
kirbot
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Well, I didn't have a chance to work on it much today, but I did bypass the fuel return line that I added, just in case that was dropping the fuel pressure. But... it didn't help any.

I just tightened the idles screws and backed them out 2 turns each. ( they were at 3 turns)
I don't have a vacuum gauge but from I read 1.5 or 2 turns is a good starting point. It may have popped through the exhaust, but I don't remember it backfiring through the carb at all.


I don't have a gauge to check the fuel pressure, but I do actually have a spare pump laying around. I'll probably throw that on, and if it still doesn't help, I'll have to get a pressure tester.
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Unread 01-01-2014, 05:55 PM   #8
kirbot
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I finally got a chance to work on it again, and... Success!
I just cleaned out the carb and now it seems to be running fine.

It still bogs like hell when I floor it, but at least it runs again.
I did pick up a fuel pressure gauge from harbor freight the other day, and it's running psi, so it looks like I'll probably be looking for a regulator for that next.
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