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nick
nick, ASE Certified Technician
Category: Jeep
Satisfied Customers: 65
Experience:  jeep specialist
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My 93 jeep cherokee 4.0 wont start after battery was disconnectd

Customer Question

My '93 jeep cherokee 4.0 won't start after battery was disconnectd for quite awhile. Ran diagnostic scan which showed no trouble codes. Did I somehow affect the computer or the security system with prolonged battery disconnect? Any other ideas?
Submitted: 7 years ago.
Category: Jeep
Expert:  nick replied 7 years ago.

HI gamble,

my name is XXXXX XXXXX I can help you. just need a few things. did youleave the positive battery hooked up and just is crank over or what does it do when you try to start it?

Customer: replied 7 years ago.
Nick.
Sorry, I got disconnected. Here's further info on my problem:
Batery is properly connected. Engine cranks, but won't start. If I reset my auto alarm system then itthe engine fires for a split second and quits. Once again it will then crank, but won't start.
Expert:  nick replied 7 years ago.
so you have an after market alarm system on this jeep?
Customer: replied 7 years ago.
No, it is oem factory.
Expert:  nick replied 7 years ago.
is there a way you can look under your knee blocker and see if you see a module underneath there. that should be where your alarm system is. IS this a Grand cherokee or just a regular cherokee
Customer: replied 7 years ago.
My car is a regular jeep cherokee larado, 4.0 liter. straight six. Yes, there is a module uner the dash. Yesterday, I called an auto alarm specialist and he came to my house. He unplugged the module and pluugged it back in to reset the alarm system. He also unhooked the battery and hooked it back up to try and reset the system. He was unsuccessful with both proceedures. He was unable to fix the problem.
Expert:  nick replied 7 years ago.
did he just unplug it from the module or completely disconnect it. I know that I have run into situations where the alarm has to be completely disabled from vehicle. but I know you propbably don't want to mess with it. Do you have a test light or volt meter that you can used. I think this might be a little lengthy to determine what exactly is going on here>
Customer: replied 7 years ago.
The auto allarm specialist unplugged the module completely. Is that a complete disconnection or is there a further proceedure needed to completely disconnect the alarm system?

We have volt-ohm meters (analog & digital), a test light and a scanner. Let me say again, that when we scan the system it indicates no trouble codes. The check engine light internal system also indicates no trouble codes.
Expert:  nick replied 7 years ago.
yeah, the problem is the starting wire (yellow) goes through the theft module then to your computer. I guess what I need you to check is when trying to start your jeep use your test light on the front of the yellow wire see if it lights. then check that wire on the other side of the module if it doesn't light up then the module locked up and you will have to completely removed it with all of its wiring. so let me know what you come up with
Customer: replied 7 years ago.
Ok, thanks Nick. We are going to go check out the situtation as per your instructions and get back to you, hopefully. This web site is a bit tricky. How long will you be around today?
Expert:  nick replied 7 years ago.
well I check in frequently so I will be on and off for the next few hours. If you do find something wrong and and I helped you please accept thats the only way I get anything for helping if not feel free to ask anything else and I will see what I can do for you.
nick and 5 other Jeep Specialists are ready to help you
Customer: replied 7 years ago.
Nick,
Need to know if the "theft" module is the same as the security alarm module I have located uner the knee blocker on the driver's side. The security alarm module is a 21 wire plug with only one yellow wire. I can't determine if it is going in or coming out.
Expert:  nick replied 7 years ago.
Yeah, that is the same module really the only what to determine weather going in or coming out is follow the yellow wire from your steering wheel test it there. somehwere next to that connection they will have tapped into the other side of the wire. so you have to check both. does that make sence?
Customer: replied 7 years ago.
Nick,
Just called the auto security alarm specialist that checked my jeep yesterday. He said that the module is working properely and is not blocking ignition to the computer. Where do we go from here?
Expert:  nick replied 7 years ago.
ok other then this module guy that says it is ok have you performed any other repairs?
Customer: replied 7 years ago.
No, and when we run scans they always indicate no trouble codes!

Again, I'm wondering, in your experience, does disconnecting the battery for a prolonged period ever affect the compter? If so, might I need to have the computer reprogrammed?
Expert:  nick replied 7 years ago.
The answer to that question is no. THe only thing that happens is all the capacitors drain. I don't think that is the problem. One more thing on your scan tool is there a way you can watch sensors while trying to start it? Have you checked Fuel pressure?
Customer: replied 7 years ago.
Nick,

We will try to scan and read sensors. I don't think we have a sensor proglem, though, or the security alarm guy would have picked-up on it.

Well, that's about it then. Thank you for your help.
Expert:  nick replied 7 years ago.
not always. I was just curious about something I know you might not think this but the crank sensor might not be getting seen and that could be why sometimes it spits and sometimes it won't start. this is a common problem. So I was just trying to narrow down some causes. I have found it gets pretty hard to diagnois a vehicle without even looking at it. but I would say if you can look at the crank sensor while trying to start it. if you see the numbers count then it is working. if you don't see any numbers counting from the crank sensor You have a bad sensor. Thanks for sticking with me here. this is kinda a fun tough one that I want to fix for you
Expert:  nick replied 7 years ago.

Ok so I don't think you will be able to read those sensors. I forgot what year I was working on. SO sorry. so one other thing that I think you really need to check is your fuel. How long has this vehicle been sitting and how much fuel is in it?