[jdsalas]

this just happened to me. there is a good possibility it is the CPS (crank position sensor. When you look through the forum you will see no spark with everything working usual ends up being the Crank Position sensor (CPS). The jeep will not start if this has a problem.

DIAGNOSTICS: There is a wiring harness that follows the fuel injector rail and comes back out behind the throttle body. One of the connectors from that wiring harness goes back and down to the transmission. If you follow that wire to the end you will see a black sensor near a open in the transmission with flywheel with teeth. this is secured by two bolts. Now, the connector has three wires, left, middle, right. with a ohms meter check the middle wire to the battery ground the reading should be less than 5 ohms. If higher than the wiring needs repair or replacement. If OK than turn the ignition on but don't start and voltage probe the middle wire with one of the outer wires (middle and left or middle and right) to find out which one is giving out over 5 volts. next voltage probe between the middle wire and the one that did not have voltage and with the probes connected have someone crank the engine, the voltage reading sould be alternating between 0.0 and 5.0 volts or averaged out to 2.5 in some voltmeters. The book (chilton) says if the voltage reading is not as specified above the sensor maybe faulty. Which is the conservative way of saying it's broken and you need to replace it.

REPLACING 4.0L inline6 CPS: the swivel socket and a couple of 8 inch extentions. then come from underneath left wheel (from behind left front wheel). more easier for people with small arms. also my suggestion is to stick a crumble newspaper page right undernneath sensor to block the bolt from falling in the hole. I was lucky the magnet on the sensor was still strong enough to hold onto the bolt. I could see it already.... a simply replace job turn into a major tranny dropping job or something and all I am is a shade tree mach.