Gee oh Dee

I dunno about you but I try to keep rocks and tree limbs out of my engine bay, and away from anything under there.

So far I've been 100% succesful.

I'd like to see someone manage to put something far enough into the engine bay to knock something loose. I'm willing to bet in 99% of off road situations this is near impossible to do.

This is almost like saying its possible to knock off some plug wires or your cap. Sure, it COULD happen, but its not likely at all.

HenryR

Bingo! The retainer clip that holds up the rear O2 sensor wiring came loose so the wires were rubbing against the driveshaft. Two bare wires were shorting out. Thanks for the help!

matt_101

matt_101

I replaced the sensor, it still doesn't start. Same situation as before, no spark.

I am suspect of the shift linkage. Apparently this jeep was know for not starting if it was not completely in park. when i changing the sensor i ened up moving the shift linkage back and forth some. When i tried to start the jeep it would not even crank, i moved the linkage by hand under the jeep and it cranked once i got it back into what i am assuming is the correct position. I don't have the bracket for the shifter back on, as i just wanted to try and start it to verify if the CPS was in fact the problem or not.

So, new cps - still no spark.

How do i make sure the computer knows the jeep is in park? would it try to crank and not have spark if there was a problem with the shifter? Can i jump this? like you can jump the neutral safety switch in a manual transmission vechile?

Well anyways, here are some pics showing how to remove the CPS - i could not find pics anywhere. as you will see you need the universal on a 90 degree angle.





HELP ME PLEASE.

CrazyMacaw

I think you misunderstood what I was saying.
The other poster was complaining about the location of the CKP sensor being way up in a PITA place to get to on top of the bell housing so my reply was saying if it was in an easier place to get to like further down the bell housing on the side or bottom where you could get to it really easy it could easily get damaged by a limb, or rock or even road desbris. My point was that while the location of the sensor is a pain to get to for replacement it's well protected.

matt_101

It is defiantly well protected. but they should have clearanced the top of the transmission tunnel to allow you to remove CPS from the top.



but bummmmp..................... i want this thing to start.

if the neutral safety switch is bad, will it crank but not have spark?

Gee oh Dee

I'm not sure if it will or not but there is a thread on here with someone trying to replace his. You may wanna search for that thread to see if he has the same issue you are having, maybe that'll answer all your questions.

matt_101

I got back at it tonight for a while.

-put the shift cable bracket back into place
-checked voltage at the coil, i probed the connector as shown in the pic below and grounded the meter directly to the battery. i got 0.01 volts with the key in the run position, and i got 0.14 when i cranked the jeep. Is this the correct way to check the coil for voltage? i would have though it would need much more voltage to create a spark. Which part of the connector should i be probing?

If i tested the coil correctly - what can cause little to no voltage at the coil?

all fuses are good.

Also, i cant find the neutral safety switch - i only want to jump it to see if its the problem. I'll replace it if it is. Anyone have a pic showing where it is located? i understand its on the opposite side of the transmission of the shift cable, but i still can't find it.

ET JEEP

The NSS will not cause a no spark condition. All it does during starting is provide a path to ground when the transmission is in park or neutral. This allows the engine starter relay to activate and engage the starter.

Check your ASD relay and make sure it is good.

Check these two links and see if they help.

No Spark

No Spark 2

matt_101

Thanks very much!

To check the ASD relay i swapped it with the starter relay and the jeep still cranked with the ASD relay in the starter slot. so it has to be good right?

I am thinking this is a computer issue, do i need a computer from a grand cherokee? i cannot find any for a grand cherokee but there are some regular cherokee computers around. The reason i suspect the computer is that the jeep was used to boost another vechile when the JEEP WAS OFF. It hasn't started since that. weird i know.

so.....

theres a new crank sensor in it from here i am thinking:

-cam sensor
-new pcm ( most likely problem?)
-broken wire
- anything else i could be missing?


i was also talking to someone local and they informed me that there jeep suffered from a no spark condition because of a bat coolant temp sensor. How likely of a problem is ?

If i get a OBD II scanner - will it tell me if i have a bad computer?

Thanks again i guys, i appreciate any and all continued help. i would love to get this on the road.

ET JEEP

If the engine cranked with the ASD relay then yes the relay is good. During start the PCM reads a few sensors and it could be a bad sensor. You would need to get a manual to see how to do the testing of the sensors. I would try that before buying a PCM. Test the cam sensor. There is some info on the second link that I posted. Also look at the O2 sensor. Check the wiring and make sure it is sound.

If you get a scanner it may give some more info. Not sure if it says whether the PCM is bad. There was a thread I read where the PCM developed leaking capacitors which caused a no start issue. Not sure what model it applied to. I will see if I can find that info and check.

In one of your post you mentioned a manual transmission. If you have a manual you do not have an NSS. The manual tranny has a clutch switch.

matt_101

Thanks.

The jeep is actually has an automatic transmission.

I will look into the cam sensor and 02 wiring. Both "look" fine. I read through the links you gave me - only thing i haven't done yet is test the cam sensor...

however i did go through the troubleshooting procedure for the coil....... followed the flow chat all the way through and it lead me too "replace PCM". At that point i figured we might as well pull the computer and see if there is any obvious damage...... the pics speak for themselves. I am not 100% sure if the computer is the problem but i will replace it anyways given its appearance.










so now i have to track down a computer. anyone know off hand which ones will work in my 1998 grand Cherokee 4.0?

Gee oh Dee

Holy crap, that is a BIG problem!

Bustedback

I think you may have found the problem.

matt_101

So does anyone know what my options are as far as replacement computers go?

Does it have to be from a 1998?

Can i use a computer from a 4.0L NON GRAND cherokee?

thanks.