HELP!!! No Spark-- NOT CPS! I'm stranded!

I have a 1999 Cherokee Sport 2wd 4.0 that I bought with a blown motor. I put a 2000 4.0 motor back in it using all the external parts from the 1999...

NO Spark. I am getting voltage to the plug that plugs in the coil, but no spark out of the coil. Replaced the coil---- still no spark from the coil lead into the cap.

The truck was running when I drove into the garage 4 months ago...although it was missing a piston it would run and make a hell of a racket!

3 Questions----

1- could it be the distibutor? does the distibutor have to be "good" in order to get the coil to fire.

2-I dont THINK it's the CPS, when I unplug it with the ignition on, the check engine light comes on and immediately goes back off when I plug it back in. I also hear all kinds of electicss turn back on when I plug it back in, so I ASSUME its good. Could it still be the culprit?

3-I used the flexplate off the 2000, going back in a 1999.... did I screw this up? I know the 2000 is a distributorless ignition, but it still uses a CPS and the flywheel as a pick up right???

any help would be greatly appreciated!

OH-- btw, it is not throwing any codes!

Ok, it's NOT the disrtibutor. I took a $120 gamble and bought one and it still won't fire. Anybody got any ideas?

Does the check engine light come on when you turn the key to the run position? If it doesn't and then comes on when you unplug the CPS it could be a shorted CPS. A shorted CPS will kill the check engine light when the key is in the run position on earlier years, it may also do that on the 99. The check engine light should normally come on when you turn the key to the run position, for a few seconds, as a test to make sure the bulb is working.

The electrical path to the coil is power from the ASD relay to the coil plus, then from the coil negative to the PCM. The PCM fires (pulses) the coil on the ground side. No pulse signal (or corrupted pulse signal) from the CPS to the PCM and the coil (PCM) won't fire high voltage.

Another sensor shares the sensor voltage supply with the CPS, I don't know exactly which one, but will look it up and get back to you. If that second sensor is shorted you get the same issues as a shorted CPS. The CPS is most likely IMO, but it may another sensor.

I looked in the book and the orange wire to the CPS and the cam position sensor is the 5 volt sensor suppöy wire, they share the same 5 volt power supply. Either one (or the wiring) shorts out and it can cause what you describe.

97-2001 should all be the same CPS so unless it's bad it's likely not your problem.

The check engine light does come on when I turn the key to the on position. The itt goes off before I crank the engine. I am going to switch the asd relay with the a/c relay and see if it fires.

ASD relay wasn't it...swithed the starter relaly with it and still no fire. You say the CPS and cam postion sensor share the same 5 volt power supply, as far as I know the 99 has no cam position sensor, only the crank position sensor. right? unless it is in the distributor???

All the same flexplates 91-01 too, so that's not a concern.

The 99 has a cam position sensor, it's a pickup that goes into the distributor, with a 3 wire cable coming out.

Its got to be the cps then... sigh, going to get one today.