crank, no start when hot

89 laredo auto 4.0

This has been going on for a month or two now but is getting a lot worse. It will start fine when it has sat for a while but if it was just running it wont start. i have been lucky for the most part and could wait 20 minutes or so and then it would start but the other day getting gas it wouldnt restart and i had to leave it for a couple of hours. the battery was almost dead from trying to start it earlier in the day so i had someone take me back and brought jumper cables. i tried it before we put the cables on and though it was cranking extreamly slow it still started.

Im not even sure where to start to check. It is definitly tempture related because if it has sat for an hour or two there is never a problem.

Thanks in advance for any help

Try unplugging the CPS connector and plugging it back in when it happens.

Or, you could test the CPS output voltage. It's probably kinda low when cold and too low when hot.
Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the 3.5 range on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.