perplexing starting issue
 

Howdy all, i have a 97 XJ with the 4.0l, that i bought last week. its got 215k on the clock, 195k on the motor. I noticed when i bought it, it periodically would run rough (like it was missing) at idle speed. It quits when i give it a bit of gas, and it runs normally. There isnt a engine light on, so i figured i deal with it later.

So, tonight i did the oil change, driveline fluids, etc. Just general stuff for its emissions test. So after i completed the oil change, it had its running rough issue. I gave it a bit of gas like i normally would, but it never came out of it right away. Eventually it did, and i never thought any more of it.

SO...im backing out of my driveway, and im sitting in reverse, waiting for the traffic to go by. And it dies. It cranks, but no starting. Ive got as far as connected my OBD2 code reader, and i fails to connect. There isnt a engine light on either.

Any ideas where i should look, sensors to test, etc? Ive still gotta check for fuel and spark, but im going to do that in the day light. Any input would be greatly appreciated.

Cheers!

Sound to me like CPU

If you have fuel and no spark it's probably the CPS (crank position sensor) located at the 11 o'clock position on bellhousing. Wiring comes up to the end of the fuel rail.

Pretty common problem on our Jeeps.

if the CPS was bad, would it cause the engine light not to come on/ and make my scanner fail to read the ECU? What are some other symptoms of a failed CPS?

if the cps is bad the engine light shouldnt come on. ( i think ) and you can check the voltage to the cpu and see if its outputting any.

Sounds to me like CPS. I just recentally fixed one and no it didnt make my check engine light come on. Just died. Little bit of a tedious fix too. XD

ok, so went out and had a look. Ive got no fuel and no spark. I went ahead and pulled the CPS off to have a look at it, and there is corrosion through the one side of it. Does anyone have any info on specs for resistance checks, etc? It would be much appreciated

Hope this helps..

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

Replace the cps, they go bad. You are trying to scan with the key on right?

thanks for the link. I did a resistance check on the CPS and heres what i found. Between A and B terminals i got 6.2 ohms. Between B and C i have 4.4 ohms and between A and C i have 18 Ohms......Something aint right there.