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Unread 04-15-2012, 08:43 PM   #1
nickbrooks35
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1998 ZJ 
 
Join Date: Apr 2012
Location: moncton, nb
Posts: 11
ZJ wont start

Okay, so I just replaced my transmission in my 98 Jeep Grand Cherokee. The transmission was a 42re, the one i replaced it with was from a 93 grand. Now im told that one was eletrical and the other was mechanical or hydraulic im not sure.. but the two trannys looked identical, before I made the switch i had to replace a censor... this was the one under the shifter which I believe is the Neutral Saftey Switch... although im not sure, the reason i had to change it was becuase the connectors were different, they were both three pronged but had a different plastic casing. Anyway when i pulled both sensors out they looked identical in length shape colour etc.. so i didnt think anything of it. Well now I got everything back together and the Jeep wont start when i turn the key, Battery is fine and so is the starter. I can start the jeep by touching the two bolts on the starter together with a screw driver and the jeep runs fine.. but i still cant start it with the key. I tried starting in Neutral and park, still nothing, tried playing around with my shifter and nothing.. It sound like a faulty neutral saftey switch to me.. but I cant be certain, whats your thoughts and I am also wondering if i missed a step or somethin.. is there a difference in the two transmissions that would cause this problem? Im pretty stumped on this one..

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Unread 04-16-2012, 03:28 PM   #2
Chingchase
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1993 ZJ 
 
Join Date: Sep 2011
Location: League City, Texas
Posts: 11
I have a question, does it just struggle to turn over, or does it just not even do anything but go straight to Aux? Because I'm having a problem with my ZJ not starting, but it's because of the security "Flash to pass" crap. I had to click unlock on my fob to pass the starting codes to pass security, but then my fob stopped working all of a sudden at a gas station. My only suggestion would be to check the security system first off. But that's only if it doesn't even turn over.
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Unread 04-16-2012, 03:39 PM   #3
98mopar
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1998 ZJ 
 
Join Date: Feb 2011
Location: desoto, kansas
Posts: 262
I am not sure what tools you have, but just a voltmeter can tell you a lot. If you are not sure on the NSS then get out a volt meter and locate the NSS circuit and follow it until you cant find a signal. If you have a signal, then I would suspect your ignition switch. Same deal, with a volt meter you should be able to check it and see if you are getting 12v to the starter relay.
I use a PowerProbe. It is like $100 and you can do so so so many awesome things with it, that help diagnose these sort of issues.
But at minimum you will need a volt meter and a few wiring diagrams. You really just can't go throwing parts at something like this.
I would have at least of checked the casting numbers on the transmission, before I did a swap. I know these Jeeps are really really picky as far as what parts can actually interchange.

Good luck.
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--- 1998 ZJ 5.9 Limited - 4" lift, 31 x 10.50 15, Jet chip, Kenwood Excelon everything, current DD
--- 1996 ZJ Laredo - Parts parts and more parts
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Unread 04-16-2012, 03:50 PM   #4
dusterdude
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1996 ZJ 
 
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Location: hopewell, va
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If it is indeed the nss,you can jump the harness at the conector and it will bypass the nss circuit
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Unread 04-16-2012, 06:51 PM   #5
nickbrooks35
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1998 ZJ 
 
Join Date: Apr 2012
Location: moncton, nb
Posts: 11
I do have a voltemeter. Ill check it out in the morning, and how do you jump the circuit? And to the other question no it doesnt even turn over. U
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Unread 04-16-2012, 06:53 PM   #6
nickbrooks35
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1998 ZJ 
 
Join Date: Apr 2012
Location: moncton, nb
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Also i dont think it is the ignition switch because it was all working fine before the swap. I just found out that the transmissions were the same just one is older. The only difference was that nss and the torque converter bolt pattern but thats okay
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Unread 04-17-2012, 07:38 AM   #7
JS97ZJ
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1997 ZJ 
 
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The difference in the switch wiring might not be compatible or shift cable is might need to be adjusted? If the NSS thinks it's in 1st gear, it won't allow the engine to turn over.
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Unread 04-17-2012, 08:47 AM   #8
dusterdude
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Jump the the plug on the wiring harness then you take the nss out of the equation
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Unread 04-17-2012, 02:07 PM   #9
nickbrooks35
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1998 ZJ 
 
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Location: moncton, nb
Posts: 11
Im just going to replace the nss its 40$ at napa
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