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98 Jeep Grand Cherokee 5.2 won't start

3K views 19 replies 8 participants last post by  3Recon 
#1 ·
This is my first post and I'm no mechanic. My buddy who takes care of my Jeep took a quick look and will be back later to see what he can do. It has been sitting for a month and this morning I left at 0500 to do some errands. She started right up as usual and I did a couple of stops--about ten miles or so. Went to the Post Office, came out and when I went to start it, it cranked fine (plenty of fuel) but when it started, it sounded like when you shut a car off and it wants to keep running. I drove it about 30 feet and that was it. It cranks fine but won't start. My friend connected his AutoScanner under the dash and nothing. We've checked all the fuses-- under the hood and in the right kick panel and they are all good. Speculation thus far is that it could be the computer. If so, where to get one? Thanks for any suggestions! Right now, I'm from Boston and have had the Jeep towed to his place in Connecticut. Yup, got my tired old feet planted firmly in mid-air!
 
#2 ·
When you first turn the key to the on position, does the check engine light illuminate? If no, something is most likely up with the PCM.

Check the wiring for the rear o2 sensor. Sometimes they get wrapped up in the driveshaft.
 
#5 ·
Might want to check the pin out for the OBDII port and see if its getting power and ground. I can provide a pinout from the FSM later on, dont have time to look through the FSM at the moment. The scanner should at least come on, even if it cant communicate with the PCM.
 
#6 ·
DLC pin#16 would be first place to look for 12v power for scanner. iS THERE 12V #16?

No start
have spark several plugs?
Have fuel pressure, ? use a gauge.

As someone cranks engine spray some carb cleaner into TB - did it fire and try to start on spray?
 

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#7 ·
I've owned 2 of these with the 4.0 inline 6 engine and the starting issue I have experienced on both has been a failed crank position sensor. Not sure if that's even a thing on the V8 version but they do fail and when they do it'll crank forever and not start. Perhaps someone can chime in who knows more about the 5.2 engine.
 
#12 ·
Thanks for your responses; they are most appreciated, truly!

Glen called me a bit ago (he gave me a car to get back to Boston; some friends are like that ,eh?). Here is the update he spoke of over the phone:

  • What we found was there is power on DLC 16; have NOT checked the two ground ports yet (#4, #5) Wasn't aware to check that until I read the copy of this post that Al sent me.

  • Checked all the grounds on the vehicle and replaced the ground strap that went from the engine block to the firewall which was broken (but that didn't help anything)

  • There is spark on the coil going into the distributer but NO spark coming out of the distributer to the spark plugs

  • Installed a new distributer cap, a new rotor and a new module inside called an ignition pickup module and still no joy

  • The Ignition Pickup Module has a plug on it that has three wires in it and I don't know what they do or where they go because I don't have a wiring diagram for the 98 Jeep Grand Cherokee Limited 5.2 yet

  • Have looked and cleaned all the ground connections we could find and still no luck on a display for the scanner (as said before, have yet to check those ground connections you've suggested on ports #4 and #5)

  • Observation: Whatever that module is in the distributor and the three wires unknown to me as of this time feeds back into the engine harness so those three wires whatever they do, one is not getting / giving whatever signal that it is supposed to be and I'm assuming that it is all going to lead back to the PCM. There's got to be a connection with the fact that the scanner is not turning on even tho there is power there #16 (most likely a ground issue), the fact that the spark plugs aren't getting any spark-- that it is a power issue and most likely a ground issue-- that if I knew what those three wires did in that ignition pickup module one of them most likely is a ground and it's just not there. Further, the question is are those HARD Grounds or ELECTRONIC Grounds from the PCM?
 
#16 ·
What we found was there is power on DLC 16; have NOT checked the two ground ports yet (#4, #5) Wasn't aware to check that until I read the copy of this post that Al sent me.
Check the connector grounds as well.

There is spark on the coil going into the distributer but NO spark coming out of the distributer to the spark plugs

Installed a new distributer cap, a new rotor and a new module inside called an ignition pickup module and still no joy
Check the coil connector if there is +12V going into it, dark green/ orange is power feed and grey/ white is ground.
Check coil primary and secondary resistance to see if coil is good; primary should be about 1ohm, secondary ~11-15kohm.
Check if the coil output spark wire gives good spark - test on known good ground point to block when someone is cranking.

If coil is good and it gives proper strong spark, you should have spark from the secondary spark wires to plugs if the distributor cap & rotor are good.

The Ignition Pickup Module has a plug on it that has three wires in it and I don't know what they do or where they go because I don't have a wiring diagram for the 98 Jeep Grand Cherokee Limited 5.2 yet
The plastic plate with the plug in it is the cam position sensor; what it actually does is it provides PCM with the information when to fire the injectors and when to shut them off.
Distributor alignment is VERY important on these for the fuel sync to be correct. With the #1 at TDC, distributor rotor should be aligned with the slot in the cam sensor plate. If not, rotate engine once full turn and check again.

Cam sensor has three wires; one is giving +5V sensor feed, one is ground and one is sensor output. White/ black is feed, black/light blue is ground, grey/black is signal.

Further, the question is are those HARD Grounds or ELECTRONIC Grounds from the PCM?
I highly suggest getting a factory service manual (FSM) if you don't have one, it is essential for diagnosing things like this. There are both hard grounds to chassis/ battery, and there are PCM- controlled grounds.
Sensor +5V is fed through PCM, most 12V feeds come from the PDC (direct fused feed or through the ASD relay).
Spark timing is fully controlled by the PCM, ignition coil is ground controlled.
Fuel injector pulse width/ timing is PCM controlled on the ground circuit.
Quite a few other things are ground controlled as well.
 
#17 · (Edited)
It sound very familiar. I can't diagnose this over the phone as they say. But it sure sounds like the failed solders on the PCM connector. Or simply a failed PCM. There is a story behind it. My 97 had a similar problem as did a 2000 Stratus. Do not attempt to fix this yourself. There are several online places where you can exchange or fix your PCM. I bought a reconditioned from one of those places. Has not happened since.
 
#19 ·
Check the coil connector if there is +12V going into it, dark green/ orange is power feed and grey/ white is ground.
Check coil primary and secondary resistance to see if coil is good; primary should be about 1ohm, secondary ~11-15kohm.
Check if the coil output spark wire gives good spark - test on known good ground point to block when someone is cranking.

If coil is good and it gives proper strong spark, you should have spark from the secondary spark wires to plugs if the distributor cap & rotor are good.
Timo_90xj got it right! I've my Jeep back here in Boston. Glen reports that it was the coil. It gave spark but not strong enough. It didn't come to light until it failed. Backtracking, he was going to check the ohms as suggested but the coil failed before he got there. Thanks for all your help, guys; much appreciated! Be well!
 
#20 ·
On my 98 I started chase parts, ended up throwing a PCM at it but had skipped one thing. With one bank having a lean condition and other components and that was doing a fuel pressure test. Turned out that fuel pump won't show up with OBDII and it was working intermittently with 89k and no per warning.
I better go back and read the last few post
 
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