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Unread 07-07-2011, 02:50 PM   #1
jetboy287
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93 zj starting problem

So the other day I went to go somewhere in the jeep and she wouldn't start. It would turn over like normal but just wouldn't run. I couldn't hear the fuel pump running so I banged on the fuel tank and it didn't change anything. So I popped the hood and I heard a relay start clicking. Tracked that down to the auto shutdown relay, it clicked five or six times and when I tried to start it, it turned right over. The jeep is a 1993 Jeep Grand Cherokee with the 4.0L I6 with an auto tranny and 4x4. I swapped out the relay with a known good one and it made no difference. I also pulled the ecu and cleaned all the plugs and regressed everything because sometimes it helps to mess with the plug on the ecu to get it to crank. It hasn't given me any check engine codes. What could it be. Please help!

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Unread 07-07-2011, 03:59 PM   #2
JeepFreak1982
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I had an intermittent no start issue with my 95 XJ and it was the CPS. It would fire right up at times and other times it would just crank. When was your last tune up? Cap, rotor, plugs, wires, fuel filter, coil, o2 sensor?
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Unread 07-07-2011, 07:11 PM   #3
jetboy287
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It's possible that it's the cps but does that control the fuel pump?? I thought that it just worked the firing order. I really don't know when it had a tune up last but the plugs and wires look brand new I've only had it about a month and it's just started giving me grief. What does the auto shutdown do? What sensors does it look at?
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Unread 07-07-2011, 07:13 PM   #4
jetboy287
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Oh and side note thank you for the quick reply and trying to help me
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Unread 07-07-2011, 07:59 PM   #5
jetboy287
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Just pulled my cap and rotor cap looks new but the rotor was a little dirty I cleaned it. And my iac both. It runs fine once the fuel rail gets pressure but in order for that to happen I have to wiggle the wires around the ecu
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Unread 07-07-2011, 08:04 PM   #6
JeepFreak1982
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OK so you either have a broken wire going into the plug or you have a bad solder joint on the ECU
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Unread 07-07-2011, 08:35 PM   #7
jetboy287
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What's the cost of a new or reman ecu? I would try and swap in a known good one but I don't know anyone around here that has one. I may try and pull my ecu agin and take a look at the pins from the back possibly tomorrow. Not sure if I'll have the time I have to take a ride to the dr with the mrs tomorrow. Maybe she will grant me a kitchen pass for a few.
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Unread 07-07-2011, 08:47 PM   #8
JeepFreak1982
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You cant see the pins the whole computer is under 1/2" of epoxy to seal it front and back. Id guess $300 or so for a reman ECU Why not pull one in a JY and swap it in?
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Unread 07-07-2011, 08:48 PM   #9
jetboy287
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Would a bad capacitor on the ecu board make it do this? When I pulled the ecu the other day to clean and check it I opened the case and it looked like some of the oil from one of the capacitors had leaked out. I could see a trail in the dust on that gel stuff that they put in there.
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Unread 07-07-2011, 08:49 PM   #10
JeepFreak1982
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Absolutely
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Unread 07-07-2011, 08:50 PM   #11
jetboy287
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I may try and find one at a jy. Does it have to be the same year model? Or does that even matter? I'm new to the gc. I have had a few Cherokees but never had an issue like this
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Unread 07-07-2011, 08:51 PM   #12
JrMechanic
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Do a search, leaking caps in the PCM is common, and is a $5 dollar fix for your problem.
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Unread 07-07-2011, 09:01 PM   #13
JeepFreak1982
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The part # of the computer has to match. It will have a white sticker on it with the part # You may be able to use the 93-95 computer but im not 100# sure. Just make sure the part # matches and it comes out of a ZJ with the same engine as you have. Swap it in and go on your way. I have seen the tread about repairing the computer by drilling through the coating to get to the caps and resoldering new ones in. If your not experienced with this stuff i advise you dont do it. Doing something wrong could lead to much bigger problems.
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Unread 07-07-2011, 09:22 PM   #14
JrMechanic
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^Much bigger problem? Worst case he ruins the PCM, and will have to get another which is what you're suggesting anyways.

Buying a used one is a waste of money, it's extremely common for the aged capacitors to cause issues, this isn't an isolated problem. Odds are you'll end up with the same junk, so you may as well take an hour and $5 to fix yours correctly.
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Unread 07-07-2011, 09:29 PM   #15
JeepFreak1982
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Bigger problems as in what if he solders in new caps not knowing how to properly solder, shorts something, and that leads to blowing something else up. Shorting a sensor, another BCM, thats what i was getting at.
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