jeep wont start.....sometimes

my friend is having some trouble with her 87 XJ automatic 4x4. it runs great but sometimes it just will not start. my other friend describes:
" it would turn over, but not start. I checked it out and there's fuel pressure, I couldn't tell if the injectors were firing or not, but I sprayed some starter fluid into the intake and it didn't make a difference. I checked for spark and there was nothing. It wasn't even trying to arc at the sparkplug wires through a piece of metal to the engine block. I'm suspecting a CPS or possibly a coil. It's intermittent whatever it is."

any ideas on what could be wrong? thats about all i know with whats wrong with it...

Without an input signal from the crank sensor to the computer, the engine will not have spark and it will not have fuel going TO the fuel injector. The crank sensor is a pretty common failure.

Below is a link to a thread on the crank sensor which will give you more information. I would suspect the crank sensor before the coil or the ignition control module on an 87, but theoretically it could be any of those. The crank sensor and coil can be easily tested yourself, but not so easy to check the ignition control module.

I'd start by testing the crank sensor WHEN symptomatic.

http://www.naxja.org/forum/showthread.php?t=1044073

interesting. thanks for the link! looks like its the CPS but i guess we wont know until we actually test it.