engine died while driving. No start.

96 jeep xj 4.0L auto. ok here's the story. I had just pulled off the freeway and was coming to a stop at a redlight after exiting when the engine just shut off. No sputtering or stalling or anything, just like I had turned the key off. I do electrical work on auto's so I did my preliminary check of disconnecting the battery to reset the computer.. Same thing the engne just turns over but won't fire (keep in mind there has been NO check engine at any point). Checked fuel, it was present. Towed it home. When I got to my tools I checked for spark... No spark. The ignition coil was original hardware and I have an account with a parts store so I just replaced that for giggles.. Still no spark. The thing that tripped me out was how sudden it was that it diddnt seem mechanical at all. Did a little research and found out that apparently the crank position sensor (CKP) is notorious for breaking on the 4.0L. When this happens the engine will not start and immediately shuts off. Took it to my shop and put a scanner to it, popped the code for the CKP. Replaced it, it's located in the top right side of the bell housing and the plug is right on the fuel rail (kind of a SOB, I have big arms squeezing my hand and arm down between the motor, wiring harness, and firewall hurt like hell!!) got the 2 holding bolts with an extension from the bottom and pulled it out the top, reverse order for installation. Fired right up. Hope this helps anyone with like symptoms.

next time use really long extensions and go at it from underneath by the tcase shift linkage

in4aride said:

next time use really long extensions and go at it from underneath by the tcase shift linkage

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ya that's what I did.. About 3' long!!but I had to line it up first... That was the tough part. Dangled it down and lined up the holes, held it with a bungee, and threaded the bolts from the bottom with the super long extension. The top bolt was the hardest to get threaded right had to be prefectly straight which was difficult while using a knuckle..

Yeah, I like 1/4" drive when changing them, from underneath. Putting a little grease in the socket helps keep the bolts--special shouldered bolts--from disappearing into the bellhousing.

Glad you figured it out.

Now go have fun.

PS--welcome to !

PPS--FYI the CPS/CKP crank sensor can develop the nasty habit of a thermal failure over time--suddenly die, fifteen minutes start up and run fine, then do it again. The coils have a nasty habit of doing this too.