[TJTom00]

I was wondering if anyone had any quick answers on this. My mother-on-law's '98 ZJ with a 4.0 will not start. She drove home the previous night and it was fine. The next morning it cranked but would not start. I looked at it today. I can hear the fuel pump running when the ignition is switched on. It's not getting spark. I tried to check the coil but I am not sure I checked the resistance the correct way. I have an '00 service manual for my TJ and it mentions something about a primary and secondary resistance reading for the coil (2.5 has a setup similar coil to the '98 4.0). Judging from one of the readings I am suspecting it's the coil, but I am not sure. I tried to search in the forum and did see some info on crank sensors and such, so I was wondering if anyone had a similar experience.

One other thing, this ZJ just turned over 181,000 miles and prior to this it pretty much runs like a clock.

Any help would be appreciated. I am trying to save them money by fixing it myself instead of them taking it to the stealership. I have done quite a bit of work on this vehicle, but it's never been dead, leaving her without a vehicle during the work week. Thanks!

[CJ7-Tim]

The XJ Cherokee has issues with the Crashaft Postion Sensor on the bellhousing. Try some of these ideas.

CPS


The most likely cause of it cranks and cranks but won't start up is the Crank Position Sensor (CPS). CPS failure is very common. The CPS can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Symptoms –
-Starter cranks and cranks but engine won't start up
-Fuel gauge and voltage gauges may not work or display properly.
-You sometimes will have No Bus on the odometer after 30-60 seconds.
-No spark at the spark plugs.
-Fuel pressure is OK at the fuel rail.

If the CPS is failed sometimes the OBDII code reader cannot make a connection to the computer or cannot read Check Engine Light/MIL codes because the CPS has failed.

Crank sensors can have intermittent “thermal failure”. This means that the sensor fails when engine gets hot, but works again when it cools back down.

Diagnostic steps to confirm the CPS is the cause of your no-start

You might be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now displays correctly, replace the CPS.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU will behave oddly until you remedy this.

CPS Testing


Crankshaft Position Sensor Connector





TESTING PROCEDURE 1991 + 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (SEE Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

[gatorayde]

If it is a CPS, I wound up with an extra one (long story...) that I'm selling cheap. PM me if you're interested

[TJTom00]

Thanks for your responses! I will look into this to see if I can get a chance to check it out. Unfortunately, she may not be able to wait for me to fix it. I will research more about the CPS and maybe try to get up there to run the tests on it.

Thanks again!

[jreed80]

pull the spark plug wire off and hold it close to the cap or spark plug you should see and hear spark,also if its a automatic could be the shifter try putting it in neutral.