Hello, I've been having problems with starting my jeep grand cherokee with a 4.0L. When I turn the key, the check engine light which normally comes on does not - sometimes if I let the key remain on the on position after a few (up to 5 min)minutes it click on - that is the check engine light and it starts no problem. After the check engine light goes on the first time - if you turn the key again - no problem. I have checked the fuel pump - it is ok - I have replaced the fuel pressure regulator and examined the fuel injectors for leakage - none of these appear to be the problem or the fix. The relays at first make a grinding sound - that is with the first check engine light coming on - do you have any suggestions thanks
Assuming I understand your problem correctly, it sounds as if the car will only start once the check engine light comes on. The check engine light is controlled by the PCM (powertrain control module; or computer) which is also responsible for basically all engine operations including fuel delivery, ignition, emissions, and so on. If this light is not coming on, it means that the computer is not getting power. If the computer is not getting power then it won't start. The fact that you hear the relays click on when the light comes on is another indicator the the computer is not getting power as it also supplies power to the ASD (Automatic Shutdown Relay) which in turn supplies the power to the fuel and ignition systems. Check the ASD relay located in the power distribution center, if it is the same relay number as another un-important system, then swap it out to see if that helps. Make sure the plugs going into the computer are tight. The delay in the power going to the PCM sounds like a stuck relay, have someone tap the relays when the light is off to see if comes on. It is also possible that the PCM itself is failing.
Well the dealer will rape you for 400 or so, but there are alternatives.  Most parts stores have access to them as well for less, but not cheap.  eBay is another source, I have gotten 2 off of there, you will need to get the part number off of the PCM to find the correct one.  Prices range from $30 to $100 or so but they are used and won't have a warranty.  If you don't find the exact part number on eBay, here's a trick, you can go to chrysler parts direct and enter the part number, it usually will be superseded by another part number, and you can search for that on eBay as well.  What I found was that most of these computers were pretty much the same physically for certain years, and the part numbers just denoted the software programming of that computer.  I can't make any promises on wether a different part number will work or not, or if you can get one reprogrammed with the correct software for your model.  Good luck!
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Yes that is correct - I think you are correct re the PCM - any suggestions on where to purchase a new one? Thanks
thundergod - yes just changed all battery clamps etc - too cold here to outside and work on it - need warmer weather ...
Thanks for the info
i also have this problem i have to wait several mins for the fuel pump relay to kick in the colder it is out side the longer i have to wait but my check engine light does come on when its ready to start ....were not able to run the diagnostic test on the machine and unsure why that is
A poor ground will also give the same problem... Loading the system a number of times sometimes restores electrical contact but in time this will also fail to work ESTABLISH THAT ALL GROUNDS AND CONNECTIONS ARE GOOD BEFORE DOING MAJOR TESTING OR REPLACING OF EXPENSIVE PARTS!!!!
Battery and other electrical connections all clean and good? All ground connections OK?
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