I have a 93 cherokee. It's pretty strictly off-road only. I use it around the property for utility and to play with some occasional light off-reading. It has 4.0/5 speed, 260+k miles on it, smokes a little, but generally fires right up and drives fine.

However, when it gets warm, it will not want to run anymore, and won't start. Thought it was probably just overheating, so I pulled the thermostat and wired the electric fan to run all the time.... Still does it.

Here is the thing, it doesn't act like its getting hot. It still turns over very fast, its not steaming, no idiot light comes on, none of the tell-tale over heating signs.

Yesterday I barely drove it, it did the same thing again. Shut it off, tried to start it a little while later, wouldn't start. Left it a couple hours, fired right up. Drive it a little bit, left it idling, it died, and couldn't get started again, not even cold and pull starting it.

So I am at a loss. It's got oil, coolant, gas... I haven't checked spark yet but that is my next plan.

Anyone have any insight on this issue?

 

You gotta check for spark when symptomatic and it won't start. Easy to do on a 93 4.0 engine.

If you have no spark which is very likely, the top two possibilities are a bad crankshaft position sensor or the ignition coil. Both can fail when hot, the crank sensor fails more often.

Both can also be tested, but you would have to test these components when the engine won't start; otherwise they will likely test within spec.

If you end up getting a crank sensor, do yourself a big favor and buy a genuine Mopar crank sensor from Jeep. Aftermarket crank sensors are very "hit and miss" with a lot of miss.

Good luck and keep us posted!

 

Next occasion this occurs, check for spark and fuel. This will give some idea what direction to go.

 

^^Both of the above should help you with your problem.^^

 

Besides what has been mentioned above, search for "Heat Soak" on here.

 

I've don't believe that I have ever seen mention of a heat soak problem with a '93.

I am by no means saying it doesn't happen, I would just be interested in knowing why it might be a problem in the case at hand.

 

I have had heat soak on both a '91 and a '92. It just sounded like a problem that I have had in the past, but then, I live in Arkansas with hot and humid summers. As I agreed before, CPS would be my first check.

 

Ok, I'll admit I just went back and reread the original post. I didn't see the no start when cold part.