cliff89

I have a 1989 cherokee with a 4.0 inline 6. whenever i drive it around then turn it off and come back to leave somewhere it won't crank. i have to let it sit for atleast 45-60 mins before it can crank. something is overheating is my guess. because once it cools off it cranks right up. what could be causing this?

cranesrule

Won't crank or won't start? Are you getting it to turn over?

cruiser54

Cranking over is what the starter does. Not starting is when the starter does it's job but the engine doesn't start.

So, do you have a "crank-no start" issue?

tjwalker

Yes, "cranking" is often used incorrectly which can lead to confusion.

I'm assuming that the engine turns over (cranks) but doesn't start when hot?

If that is the case, the #1 suspect is the crankshaft position sensor. The #2 suspect is the coil itself, but the crank sensor fails way more often.

If however, it won't even CRANK (crank = turn over), then connections, grounds and the starter itself are in play.

cliff89

the engine will turn over but will not start. and the only way it will start is after it has cooled down. what could be over heating? its something electrical.

cruiser54

Try this.

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 as the CPS will test good when in fact it is bad.
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 .35 AC volts range or lower 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.
　
Revised 11-29-2011

cliff89

if you know what can fix this can you please tell me. also i need to know where to find the problem. i just go the jeep this week and its my first jeep.

The Rooster

How many miles on it? does it have spark and fuel? you need to see if it has both of those 1st..

cliff89

the motor is supposed to be fairly new. body read 232500. but it does have spark and fuel because it starts up whenever it is cooled off

cruiser54

You describe a typical issue with a CPS that fails when it's hot.

Most likely it's the CPS and I posted instructions on how to test it. If you are unable to perform this test yourself, find someone who can help you with it. Perhaps a mechanic?

There is not only one single solution for a hot "crank-no start". Some testing must be performed.

cliff89

does anyone know how to get trouble codes on my 89 4.0 cherokee limited? cant use codereader

cruiser54

Can't be done. Do what was suggested already. Studies have shown that more Jeeps get fixed with work clothes, flashlights, voltmeters and wrenches than have ever been fixed with keyboards, a mouse and a monitor.

gsrcivic

This is crazy I live in jville al and my 87 is doin the same exact thing so my first doings where the dizzy cap rotor button and plugs and wires then did the cps and it starts and runs when cool but not when hot gonna check the cps when I get a break from wrk