What's the best way to trace this to the problem. intermittently my 89xj wont start. it cranks over fine and I have 38psi at the fuel rail. even when I spray starting fluid directly into the throttle body it wont start not even a one little puff, then after 10 15 tries it starts right up like nothing happened and runs great. i'm 99% sure i'm not getting spark when this happens. any ideas on how to test or test points to check when this happens.

 

Pull the plugs out and lay them against the block. Crank it over and see if it is sparking, you will see it spark. That will 100% your no spark theory.
Start with the plugs, back threw the cables to the distributor cap and connections check for cracks or any stripes or signs of ware. Also check ignition rotor that spins in the distributor cap for corroded rotor tip or bad spring tension.

 

Check your coil and you CPS if you are not getting spark.

 

ok yesterday I installed new Cap, rotor, wires, plugs and coil. and swapped the coil module base with a used one i had in my garage. and it happened again this morning. i guess the last thing to replace is the CPS does anyone know what the resistance should be across the two wires. right now the jeep starts and i have 475 Ohms on it

 

yea i did that yesterday when i ran to the store and the problem happened and no spark so im 100% sure its a no spark issue