4.2L will crank but won't turn - JeepForum.com
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post #1 of 3 Old 08-14-2009, 04:59 PM Thread Starter
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1983 CJ7 
Join Date: Aug 2009
Location: Lake of the Ozarks
Posts: 4
4.2L will crank but won't turn

I have dreaded asking this question all week but I have exhausted all known options to myself. Last weekend it started just fine, no problems. This week, I have removed the dash and unplugged the guages to check the connectors, then plugged everything back in according to wiring diagram (NO guages were actually replaced). Also, I replaced the ignition key lock cylinder. The last two small things that I have worked on since the last time it started was I replaced the windshield washer fluid motor, and worked on the wiring harness for my headlights to get both lights to work on both settings (high and low beams). After those few things, I went today and can not get it to turn over. It just cranks and cranks and cranks but no fire. I beleive the coil has good power because I got a spark when disconnecting and reconnecting the two wires that go to it. It's the 4.2L with an MC2100 carb, other than that I can only assume the other parts are oem or oem replacements (I have only had the CJ for about two weeks now, and it ran fine as of last weekend). It's unknown to me why, in a week's time, it won't start after all i have done s mess with electrical systems, but nothing in th engine bay on the major components. Any help here would be much appreciated.


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post #2 of 3 Old 08-15-2009, 05:29 AM
Mike Romain
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1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant
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Originally Posted by gmchx4 View Post
IIt's unknown to me why, in a week's time, it won't start after all i have done s mess with electrical systems

I don't know where to start....

Off the top, there is one connection under the dash on the later ones that controls the tach. This is a large red wire off the ignition switch plug and it also controls the power to the ignition module. If you unplugged a stock tach, the engine won't start.

Then there should be two small wires off the fender soleniod in the engine bay on the side of it, maybe one got knocked off?

You need a multimeter and a helper so you can see if the coil is getting power when the engine is cranking over as well as when the key is in run. These are two separate circuits.

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post #3 of 3 Old 08-16-2009, 12:14 PM Thread Starter
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1983 CJ7 
Join Date: Aug 2009
Location: Lake of the Ozarks
Posts: 4
got it to start this morning! i feel dumb after fixing it but at least i can get back to driving her lol. it turned out to be a bad ground wire coming off the white, ceramic regulator on the passenger fender, the wire was going to the coil. anyway, the wire was shorting out and after replacing it and the connector, it fired right up, better than when i first bought it haha

thanks for the help, great info for when i go to add my tach this winter ...
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