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Unread 08-26-2013, 01:50 PM   #1
Karl4
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CJ-7 new 258 wont go over 3k rpm while driving

Just finished the rebuild on my 86 CJ-7 258. Its backed my a 999 auto. At idle shes pretty smooth. Puffs of black smoke out the exhaust. Weber 32/36 on it when I bought it and started the rebuild. I cant rev it up to 4000 rpm at idle in park with no issues what so ever. The problem seems to be while I am driving. 1st and 2nd gear no issue around 45 mph on the tach. I put my foot into it in 3rd gear and it starts to bog down and want to die. If I back my foot off it regains strength but refuses to go over aroudn 48mph on the speedometer. Fuel mix screw on the Weber is in the seated position (all the way in) and seems to have the least amount of problems at that setting. any more fuel then that at it wont stay idling. I set the timing at 8 BTDC at idle RPM (around 750 or so). I know now that it needs to be set at 1600 rpm. Could this be the cause of my problem? Its perfect around town but try and get it 50 mph or so and it just wants to die. I dont believe the Nutter bypass has been done. I'm at a loss for ideas. No one seems to have the same symptoms that I can find a thread on. Thanks in advance for any help!

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Unread 08-26-2013, 02:30 PM   #2
kovic
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Something is wrong with the carb. Mixture screw should not have to be screwed all the way, it should be around 2 or so turns out. Sounds like its flooding a little, you mentioned black smoke at idle, thats too much gas.

Read this on how to properly set it up. http://www.redlineweber.com/html/Tec...lean_best_.htm

But it sounds to me like you are getting to much gas, maybe your secondary throttle plate is open too far, take the carb off and check.

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Unread 08-26-2013, 02:44 PM   #3
LumpyGrits
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Ck you accelerator pump and float level.
Whose tach are you using?
LG
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Unread 08-26-2013, 03:32 PM   #4
Karl4
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Kovic,
Tried your changes to the carb. wouldnt stay idling. Thought I returned everything to what it was took it out on the road. it lurches and boggs down at around 35mph now. Just put the carb on the other day and it appeared to be at the 5mm opening for the second throttle that was explained in a different post. Please correct me if im wrong

LG-
I will google how to check the float level and accelerator pump. hopefully thatll fix it. I am using whatever tach was in there Sun Super Tach II. Appears to be near to what I am used to hearing for that RPM.

Sorry for the noob questions, but this is my first 258 experience and havent owned a carb vehicle since 99.
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Unread 08-26-2013, 03:39 PM   #5
LumpyGrits
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Disconnect the tach and take it for a drive.......
Get a REAL Factory Service Manual(FSM)!
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Unread 08-26-2013, 04:05 PM   #6
kovic
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Here, Read through this. Its a thread I started when I too was having issues with my Weber. Lot of very valuable information, and good pictures to help you check the secondary and measure the float height. Great Info from the late McMud and many others.

http://www.jeepforum.com/forum/f8/ho...weber-1365422/

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Unread 08-26-2013, 05:55 PM   #7
Karl4
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I have a Chiltons...although old its helped at times. Thanks for the link I will read through it. I found the REAL mixture screw. Black smoke eliminated. Still having the same issue of lurching and bogging down at around 35 mph 2200 rpm.
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Unread 08-26-2013, 06:37 PM   #8
BagusJeep
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Are you sure your distributor is working? Have you checked the mechanical advance with the timing light (disconnect the vacuum hose and rev to about 2300 rpm) and the vacuum adance (connect it to a manifold vacuum source and the timing should jump)? If the advance is not coming in it will not rev very high.

The 1986 has a computer that interferes with the signal from the distributor, a Nutter bypass will take 10 minutes and will eliminate this part. As you have a Weber the computer is not controlling the mixture anymore so is surplus.

Once Nuttered set the timing to 8 degrees at idle with the vaccumm advance disconnected.

Last thing to check is that you have the distributor sensor wired up the right way round and that the engine is properly earthed back to the battery. If the engine is not fully grounded the spark will not be generated at the spark plug.
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Unread 08-26-2013, 07:11 PM   #9
swatson454
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Quote:
Originally Posted by kovic View Post
Here, Read through this. Its a thread I started when I too was having issues with my Weber. Lot of very valuable information, and good pictures to help you check the secondary and measure the float height. Great Info from the late McMud and many others.

http://www.jeepforum.com/forum/f8/ho...weber-1365422/

kov
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Unread 08-26-2013, 08:17 PM   #10
Karl4
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Bagus,
Thanks for the tips I will make sure I try and complete the Nutter bypass tomorrow and hopefully it will fix the problems.
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Unread 08-27-2013, 05:26 AM   #11
keith460
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Yes, do the Nutter because as soon as the Weber carb went on, the MCU no longer controls air/fuel mix and distributor timing. Setting the timing at 1600rpm is another item that was done because of the MCU was controlling the timing of the distributor. That is not the case anymore when an aftermarket, or non-stepper motor carb is installed on the I6 engine.

When the Nutter is complete, shoot for 10-12 degree's initial timing with the vacuum plugged, then use with manifold vacuum as the source for controlling the advance. Dial in the Weber for best lean according to the instructions.
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Unread 08-28-2013, 03:05 PM   #12
Karl4
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Ok -
Nutter Bypass Complete. Seemed to help a little.
Timing Reset at idle 8* BTDC 6th line up from the bottom
Manually worked the accelerator pump - seems to be squirting just fine.
Both barrels of the carb (used came with the Jeep but it was running when it was removed) seem to be working just fine.

Still the bogging down and the lurching when getting upto around 35mph around 2500 rpm. I can rev it to 3500+ at idle with no problem.

Next step now is a FPR
*Sigh* damn little gremlins and 106* heat isnt making this project anymore fun

Thanks for all the assistance thus far.

EDIT - FPR didnt change a thing. Still lugging and lurching while driving.

Last edited by Karl4; 08-28-2013 at 03:35 PM..
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Unread 08-28-2013, 04:27 PM   #13
kovic
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Got a pic of your engine bay?

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Unread 08-28-2013, 05:33 PM   #14
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mcmud

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Unread 08-28-2013, 07:40 PM   #15
Karl4
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Kov,
Working on it. Takes some extra we sites, my iphone apparently takes bigger pics than this site allows. Anything specific you are looking to see?
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