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Unread 07-29-2010, 05:24 PM   #1
yjasoldasiam
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1984 CJ7 
 
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Carburetor adjustment screws?

Hi all, I got a 1984 cj7 on saturday and I have been working on it a lot. It has the 2.5 Hurricane 4cyl with a carter/weber 1bbl carb. I found the idle adjustment screw on the back but can't find the fuel/ air mixture screw. Any tips would be a great help, thanks!

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Unread 07-29-2010, 06:49 PM   #2
Ken4444
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You might check the Factory Service Manual. This post has links to the 84-86 FSM:

http://www.jeepforum.com/forum/f8/84...ml#post6991784
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Unread 07-29-2010, 07:37 PM   #3
Full Tank
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Quote:
Originally Posted by yjasoldasiam View Post
It has the 2.5 Hurricane 4cyl with a carter/weber 1bbl carb. I found the idle adjustment screw on the back but can't find the fuel/ air mixture screw.
If original your carb is a Carter YFA. A newer version of the YF.

This thread discusses a YF & may or may not be of help you.

http://www.jeepforum.com/forum/f8/ca...g-rich-932262/

A quick google suggests some YF series carbs may not have a mixture screw??

Good luck

FT
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Unread 07-30-2010, 05:59 AM   #4
CJ7VFR
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I have a 1985 CJ-7 with the 2.5 engine. From 1984 to 1986 AMC used its own 150 cubic inch engine.
This engine differs from the 151 cubic inch GM "iron duke" engine that was in the Jeeps up thru 1983.
I don't ever recall the AMC version refered to as a Hurricane.

As others have said, if its the original carb, its a Carter YFA. These are actually very easy
carbs to get running good, and are easy to adjust, and run quite well.

The air/fuel screw is actually only an idle mixture screw. It adjusts the air fuel mixture
at idle only, and anything off idle is controlled by the computer controlled items
hooked to the carb.

If the carb was never rebuilt, then the idle mixture screw will be hidden under a plug
in the base of the carb. That's probably why you can't find it.

If you are standing in front of the Jeep, facing the engine, the idle mixture screw will
be on the left side, close to the front of the base of the carb.

There should be a plug about .375 inches in diameter over the hole where the screw is
located. If the plug has been removed, look for this hole. If its stil there, you will have to pry
the plug out using a pick or sharp screw driver. The plugs are usually soft metal, and are easily
removed. The actual screw is recessed in the base of the carb about a half inch or so.

The adjustments you make with this screw will only affect the engine at idle, so don't
expect to get the Jeep to run any more rich or lean or run smoother while your driving
by adjusting it. That's not what its for.

If you have a vacuum gauge, you can hook it up to a manifold vacuum source, and adjust
the screw until you get the highest amount of vacuum.

If you don't have a vacuum gauge, then adjust the screw out until the engine starts to
sputter and run bad. Then start turning the screw in. The engine will start to run better
and then start to sputter and run bad again. Count the number of turns you made to the
screw to do this.

You want to then turn the screw out again, but turn it half the number of turns so that the
screw is now at the mid point from when it sputtered and ran bad when it was out and where
it sputtered and ran bad when it was in.

This is about the best you can do to set it without a vacuum gauge.

What I do is I have a flat blade screw driver tip on a socket that I put 4 marks, equally spaced around
the outside base of the socket part. I make the marks about half inch long so they are easy to see.

I use these marks to count as I turn the idle mixture screw in and out so I can get the adjustment
even closer.

On my Jeep, the number of full turns for the engine to sputter and run bad from in to out is about
two full turns plus a quarter turn. So on my marked socket, I count 9 marks passing by as the engine
goes from sputter-to running good-to sputter again.

So for me, I know I am at the best it can get at 4 to 5 marks, which is about one full turn plus
a quarter turn, or right in the middle of the adjustment.

Hope this helps.

Jim
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Unread 07-31-2010, 10:23 AM   #5
yjasoldasiam
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Hey CJVFR, thanks for all the information. The air intake says 2.5 Hurricane on it so I assumed that it was called the hurricane, it must not be the original intake. Still sounds like a hurricane though I already took the carburetor out and soaked it in some chem dip stuff that i found at the auto parts store because I am not yet comfortable with taking the carb apart. The jeep does run rough at idle and smokes and smells like it is running very rich. I have also noticed that the oil pressure is sitting at 0 when idling and only builds to 20 psi when revving but this is only very recently and I bet the oil pressure gauge is broken. I will look for the screw and carry out the procedure that you described and report the results, thanks for the advice and detailed instructions!
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Unread 07-31-2010, 11:36 AM   #6
JeffreyCharles
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You may have inadvertently caused yourself another problem by soaking the carb without first tearing it down. Many of those chemicals - particularly carb cleaner - are not friendly to things like rubber and plastic. The YF and YFA have some internal parts (beyond the vacuum lines you presumably removed prior to soaking) that could be damaged by the chemicals leading to the need for a rebuild with new parts anyway. Fortunately, the YF(A) is really easy to rebuild, even for the novice. Few moving parts and those easily organized as you pull 'em off. Here's the process for my older YF: Carter YF Rebuild
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Unread 07-31-2010, 12:51 PM   #7
yjasoldasiam
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Thanks JeffreyCharles, that is definitely the same carburetor I have, I'm looking for a good rebuild kit, do you have any recommendations on where to get a good kit?
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Unread 07-31-2010, 12:59 PM   #8
yjasoldasiam
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By the way, I have another small question completely unrelated to the carburetor. I did a compression check on the engine today and got a reading of 120 psi on 3 cylinders and 130 psi on 1 cylinder. I have a compression tester but I'm not sure if I'm using it right. I pulled 1 spark plug at a time and inserted the tester into the cylinder and then turned the engine over 4-5 times with the coil disconnected so I wouldn't get fire. On my gauge 120 psi shows up in the "green" but I'm not sure if this is good compression for this engine.
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Unread 07-31-2010, 05:26 PM   #9
JeffreyCharles
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Yup. I got my rebuild kit from Napa. Stopped in, they didn't have it in stock, had it for me from another store within about two hours. Less than $20. Part number CRB 25613. Store Locator | NAPA Online
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Unread 08-25-2013, 09:57 PM   #10
jeepandvwguy
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Your engine is ok you only have a bad cylinder when you have 25 or more psi difference between cylinders but that shows that one is starting to go do the compression test again but this time do a wet test take a water bottle poke a hole in the cap and put motor oil in it of coarse make sure its a dry bottle pull the plug of the one cylinder and squirt some oil in there if it increases the amount of cylinder psi then your rings are getting worn I hope that my information has helped you don't squirt too much oil as it could hydrolock your motor just a little bit of oil like less that a cap full of oil. a pistol oiler works great for this job you can buy at autozone pepboys napa and so on
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