Jeep shut off need help

88 XJ 4.0 L 6cyl auto trans

I was sitting in the car with it on, listening to music i wanted the car on so that i didnt kill the battery listening to music. anyway suddenly the car shut off. I noticed cause the needle went down and i tried to start it and it just made the cranking noise,
it kind of sounded like i wasnt getting fuel so i got out the starting fluid sprayed some in the air cleaner housing and tried to start it and it didnt come on, so i unplug and plug back in the CPS, tightened the ballast resistor wires together (my resistor hasnt been connected for a long time now) so i ruled that out. but i made sure the wires were tight and they were. so i unplug the CPS again and then tried to start the car it started and then ran for a couple of seconds then it went off again seems to be dieing out sought of?
but i have power not sure exactly what it is starting fluid doesnt seem to help none? any ideas before i break out the pressure gauge and start going into stuff i need not to?

First thing to check for is spark. Take an extra spark plug (or pull on out of the motor - maybe good to also check to make sure it is not flooded), put it in one of the spark plug wires and hold it to the head or block. Have someone crank the motor by turning the key. Look for a strong blue spark. If no spark, suspect the CranK Position sensor, technically the CKP although commonly called the CPS.

CPS testing stolen from forgotton source.
TESTING PROCECURE for 1987 – 1990 4.0 L engines
Looking into connector with the tab on top. ABC is left to right.
Test # 1

· Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.


Test # 2

· You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it

thanks man I've been out in PA for the last couple of days so i wasnt able to work on the car so ill test this tomorrow wish i had more time before alternate parking but ill have to make do with what i got. ill look for my reciept tonight so i can get a refund for the CPS being i change the thing twice