JeepinREALTOR

Hello everyone! After weeks of reading forums and doing tests, I've finally decided to ask my fellow Jeepers from the interwebs for help.

So here is my situation:

My jeep has never ran right, its a 1998 Cherokee 4 Door 4.0 5 speed manual. Its always had some sort of stutter or misfire. There has been a few occasions (when it was running) that the gauges on the dash would shut off but jeep would continue to run after being exposed to water on the trails and alternator would scream as well.

The Jeep ended up sitting all winter in my garage, come February I go to start it, dead battery go figure, after charging the battery the jeep would just crank and crank, no start and failed connection to obii scanner
The jeep still reads millage on the dash but does not show fuel level or voltage

What I have tested and checked:
-Crank position sensor reading open resistance (good)
-o2 sensors reading 5-6 ohms cold (good)
-removed and cleaned all grounds in the engine bay (battery to chassis, engine to battery, dipstick tube ground, 2 drivers side inner fender grounds, added new ground from block to chassis)
-ASD relay swapped
-all fuses checked
-battery terminals cleaned
-ecu connectors checked and look very clean

Could my ecu be bad??? Please help!!!

Thanks!!

Jimbo Slice

As it sits now, will it turn over?

JeepinREALTOR

It does turn over, but will not start.

jordan96xj

If you disconnect the CPS sensor does the behavior change with the fuel level or voltage gauges (do they start working again?). On a 98, the dead fuel level and voltage gauges that correct themselves when disconnecting the CPS is prominent clue that the CPS needs to be replaced.

JeepinREALTOR

Still no gauges after disconnecting the CPS

Jimbo Slice

Have you looked at your camshaft position sensor (under the distributor cap) yet? It was the cause of a no spark issue on my Daughter's 97.

JeepinREALTOR

Jimbo Slice , I have not yet tested that one, is there a certain resistance reading I should have on that sensor? How to do I go about testing it? Thanks!

jordan96xj

Seems like you have done a lot of sensible items already. Based on the fact that you say you observe no spark and that due to water intrusion and sitting for extended period could leave a lot of possibilities open, here is what I would do:


I would start with the ASD relay and test it for each of its control and load side functions. On the control side it gets + from ignition switch and - from computer (PCM). The load side (positive voltage at system level) comes through a fuse in the PDC.


I would start there because it will give you direction as to why spark is missing. If that relay is getting and giving everything that it should, then the no spark condition can be followed down stream to the coil.

Jimbo Slice

Sorry, I don't know that procedure. Pop it out and take a look at it. Clean everything up and put it back together... only takes five minutes.

There was visible damage on the one I replaced.

JeepinREALTOR

Thanks guys! I'll be going over the cam sensor and ASD tonight and I will report back when finished.

JeepinREALTOR

jordan96xj

Good test. But what we really need to know is whether the computer is ever providing the ground to the control side of the relay, that the relay needs to close. If it is, that means the computer is happy with conditions and wants to provide spark. If the computer is not happy with the CPS or cam sensor, it will choose not to provide the ground, and the relay will never close, and the spark will never happen. This test is what is needed to send you in the right direction (towards the computer and sensors or towards the coil).


You can somewhat do the same by testing for voltage going into the coil. Since you have already tested the + voltage at the relay. If voltage never shows up at the coil, you can kinda assume that the only missing item at the relay is the ground from the computer (this is not quite as definitive as testing the relay itself). You'll probably have to test that during cranking, because the computer won't provide that ground until it reads the cam and crank sensors and is happy with engine rpms (it needs about 400 rpm provided by the starter before it will initiate spark) this is why a weak battery or starter can also cause no spark situations, but typically you can detect a slow start/weak battery with your ears and experience.

Johnny31874

What was the final fix? Help!!!! Dealing with the same.
SO far I've replaced battery, spark plugs, coil, cap and rotor, camshaft position sensor, crankshaft position sensor, ignition switch (not in that order). Engine still cranks, but no spark. I have some fuel pressure. Vehicle ran good until it sat for two weeks.