I am having a problem with my Jeep. For some reason I can start it up cold just fine and it drives completely fine in every way. When I turn it off to go inside a store or something like that, I come back out and it wont start. I replaced the battery and the ignition coil but that didnt help. When it is cold, it starts right up every time. It is only after I have driven it for a while. I have pulled off the ignition coil wire and notice that it doesnt get spark during this weird phase of not starting. After some time it sparks fine and starts right up. Any help would be appreciated. I just got this jeep and have wanted one for a long time. I look forward to getting to know some of you guys and becoming a very common poster.

Thank you in advance

 

You could try unplugging then plugging back in your CPS.

 

Wow... thanks for such a fast response. I will do that and let you know the results. Do you mean the crank position sensor or cam position sensor?

 

Well, the cam sensor is in the distributor... I've had experience with this........


91 cherokee... 4.0HO... Would run for about an half hour... Then nothing... it would crank and crank and crank... I'd let it sit for about 15 minutes or so, it would fire right back up and run for another half hour... I changed EVERYTHING.. fuel pump, crank sensor, plugs, wires cap/rotor, fuel filter, air filter.... Come to find out it was the cam sensor... That controlls the coil.....
Simple test.......


get it not to start.
with an inline spark tester (available at autozone), plug it in to any of the igintion wires at the plug end... have someone else crank it and watch for light.. if ya got no light... you have a place to start..

 

CKP is the correct term, for the crank pos. sensor. Is at the back of the head on the driver side, should ahve a 3-wire connector.

 

Yes, the crank position sensor.

 

Ok, so I unplugged it and then plugged it back in with no change. This time it wouldn't even start while it was cold. I got underneath it and started playing with some wires/plugs/etc. and one of them felt like it was almost crumbling. I took it off and it busted right away. It ended up being the knock sensor. i went and picked one up and put it in... fired right up. I let it sit running for a while and revved the motor a bit and so on and so forth. Turned it off and it fired right back up.. went thru this for a while and it kept firing right back up... Im hoping it is fixed now. I will give an update tomorrow sometime after some in town driving...

Thanks again for all your extremely fast help. I am incredibly glad I found this site. I will be here a lot haha

 

So I start it up this morning with no problems. I drive it to my apartment about 5 miles away. I load some stuff into which takes about 20 minutes... come back out, and no spark again... Does anybody know of anything else? Do you think it could be that little base that the ignition coil sets into? could there be a fuse of some kind? Im at a loss or words. I really love this thing and want to get it going reliably again.

Thanks in advance

 

my guess is cam sensor

 

My 94 had identical symptoms as yours and it turned out to be crank sensor.

 

Ok, I will have to check the crank sensor next. Its weird to me that the thing wont spark at the ignition coil. That makes me cancel out the cam sensor since the spark isnt even getting that far anyways. What do I know tho? haha

Thanks again for the fast response

 

Ok, went and got the crank sensor... but now it is too dark to put it in. Will give update tomorrow when completed... I did notice that whoever put one in previously, only put in one of the bolts... Could that be the problem? Also, since it had the same issue this morning, it hasnt done it since. Could that be a outside temperature or precipitation problem? It is a little warmer today and the ground is dry. I wonder if the sensor could be going faulty when wet or something along those lines...

 

So I replaced the crank position sensor and haven't had any problems since. I have drove it numerous times since then and stopped the motor and fired it back up every time. I hope that is fixed for good now. Thank you again for all your help guys. I am learning a lot and look forward to being able to help others soon.

 

I have had 3 89 cherokees the current daily driver is the funniest one of all. I can drive to work about 13 miles 20 minutes drive time. No problem, let it sit all day then after work it will not start. This is not an every day process, as they say once in a blue moon, maybe once every two months. I open the hood unplug the crank postion senor, plug it right back in then it will start. If I crank mine and it will not start the first thing I do is unplug the senor, plug it right back in and off it goes. I have tested it, it tests good. One of the other 89's has had the update put in where a new plug is put in and it goes to the computer. Never a problem like this. We have changed the sensor once or twice on it over its life with us but that is all.

You may what to check on the update to elimate the problem.