no spark nightmare need some help

i have a 91 cherokee limited and one day while driving it coughed and shut off ..... tried to start it and nothing ... towed it to a buddys garage and started diagnosing it .. changed a long list of things

-cps changed twice
-plugs
-wires
-cap and rotor
-distributer/ old one had teeth worn and broken .. thought i nailed the problem there but no still no spark
had multiple skilled people time the motor and still to spark from the coil .. traced the wire back no breaks in the wire ...
checked every single fuse in the truck all good ..
checked compression it was very odd reading variations from 50 to 180 ..
so my mechanic said the crank could be messed up oil pump could be seized from the metal off the dist. sooo i swapped the motor ... got it all buttoned up new everything and still no ****ing spark im stumped the only thing i could think of it the ecu or the harness what do you guys think

if theres a new ignitor and still nothing after everything else then its a good bet ur computer has an issue. either get it checked, rewrote or a new one

Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

What year engine did they use? Did they reuse the old flex plate or use the one on the swapped engine? What engine did they swap in?

They could of damaged the CPS or COS wires during the motor swap.

i put the motor in its a 93 motor with the intake and exhaust off my 91 i dont think the cps is bad its brand new and i already swapped it just incase

I have read reports here of bad CPS (among other parts) new off the store shelf. Have you tried testing the CPS while cranking with a meter?

This prior post is where you need to start.

Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

Click to expand...

And I think there are instructions in old threads here for testing the HO year CPS sensors, new or not. If all else fails, the OBD-I ECU's do go bad.

Check out post number 14 here:

http://www.jeepforum.com/forum/f11/p1391-crank-position-sensor-cam-sensor-info-needed-1417318/

I suggesting getting the FSM test data, and get in there with an old fashioned volt-ohm multimeter and check the CPS and ECU wiring and signals.

So today I got a matching ecu and swapped it in still to no Avail so I started tracing wires and going over all plugs ... Still no sign of spark ... Tomorrow in gonna test every last thing before I give up and give her to my mechanic tomorrow ..

Have you tried following post #3 instructions? The ASD relay?

Also this thread below has how to test the CPS and wires!!!

http://www.naxja.org/forum/showthread.php?t=1062496&highlight=cps+test+start

tomorrow im gonna take another stab at it and use all the info you guys gave me hopefully ill get her to run ill post updates tomorrow

ok so today i did tome testing cps is good but still no power to the coil so like an idiot i had to get it to start so i jumped the wire with a strait feed from the fuel pump relay .. to the coil splicing the wires together and it started right up ran for a min and killed off again ... theres power all the way to the coil ... but no spark coming out .. i guess i fried the coil ... would there be any way i would be able to run the power to the coil where i wont fry the coil because im having a really hard time finding where this problem is .. any ideas