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Unread 06-20-2013, 08:23 PM   #1
ROTTEN
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cj 4.2 runs on 3 cylinders?

My father in law had me post a question for the cj guys.

4.2 with weber carb. Jeep starts but runs on 3 cylinders. There is spark on the 3 wires. Intake is clear. Compression was high,140 in each of the 3 cylinders. Were talking the back 3. Anyone else have this issue? I can answer questions

68 cj5
Rebuilt 4.2
New weber carb

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Unread 06-20-2013, 08:35 PM   #2
skizriz
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I assume you put in new plugs, wires, cap and rotor??
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Unread 06-20-2013, 08:52 PM   #3
ROTTEN
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Of course. New distributor as well. Plugs are the correct gap. Spark was tested with a spark tester on every wire. Timing was verified also.
Valves are opening and closing. Carb has the correct spacers.
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Unread 06-20-2013, 10:05 PM   #4
petey156
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Ok. Is the intake a dual plane? Where one of the barrels feeds 3 cylinders, and the 2nd barrel feeds the other 3 cylinders?
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Unread 06-20-2013, 10:40 PM   #5
ROTTEN
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That I will have to find out. Anything else I should ask about?
What if it is a dual plane?
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Unread 06-21-2013, 08:20 PM   #6
gosupes
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Quote:
Originally Posted by ROTTEN View Post
That I will have to find out. Anything else I should ask about?
What if it is a dual plane?
I don't think a dual plane manifold would make a difference on why the back 3 cylinders are lacking fuel. If spark is there and the timing order is correct, look towards the carb and how it's set up. Are the plugs even wet?
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 06-21-2013, 08:55 PM   #7
ROTTEN
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Single plan oem intake
Also he said its a ford setup. So he is going to try a points system and coil

He said the carb is clean and correct.
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Unread 06-21-2013, 10:20 PM   #8
petey156
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How did he identify that the 3 cylinders are not firing? Any chance there is a larger vacum leak near those 3 cylinders?
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Unread 06-21-2013, 10:25 PM   #9
ROTTEN
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It ran rough at idle well barely idle. Started pulling wiress to find which cylinder was a misfire. Found no change when the back three were unplugged
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Unread 06-21-2013, 10:26 PM   #10
ROTTEN
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They went through and replaced all the vacuum lines and verified they were connected.
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Unread 06-22-2013, 06:19 AM   #11
gmakra
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Could your dizzy be 180 out?
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