'89 Cherokee won't start in the heat

[Douglas Arizona]

About a week ago my jeep started acting up. Sometimes it will crank but not start, particurally when it is over 100 degrees out.

When I have gotten it started it runs fine, though there have been two cases of stalling out within 90 seconds of starting.

I replaced the fuel pump and fuel pump relay last summer and they seem to be working properly.

Any ideas? Am I correct in assuming that the problem isn't spark related since the jeep will remain running once started?

[fredjacksonsan]

Hey Doug, Welcome to AF.

My first thought based on your post is Crankshaft Position Sensor (CPS). Those are classic symptoms. If you do a search on that, you'll find a lot of information. There's also a "how to" in the DIY section of the Cherokee forum.

[johnmiltonal]

Hello Everyone

Actually i don't know exactly idea. I thought that you have to go to the mechanic shop and you can easily solve your car problem.

[mcmalloy]

next time it wont start in hot weather , take the gas cap off, it may not be venting

[Douglas Arizona]

So I've been able to get a spark to the distributor but not from it. I'm going to go pick up a new cap and rotor and see if that makes a difference.

I've read about an ignition control module. Could that cause a lack of spark after the distributor? Also could this still be the work of the CPS or does having any kind of spark eliminate that as a possibility?

[Douglas Arizona]

After replacing the cap and rotor the jeep started up with a little bit of hesitation. It is running but I'm not sure for how long. I'll put it through some gentle abuse and see if it is really fixed.

[rhandwor]

Use a 12 volt test light put it on the coil negative. The test light should blink when some else is cranking the engine. If it blinks good the pickup in the distributor is good. If it doesn't blink replace the pickup in the distributor.
Check this before replacing the module which also could be the problem.

[Douglas Arizona]

Started fine 4 times over a few hours. Then I drove about 15 miles, parked for 20 min, started and drove 90 seconds before the engine stuttered and finally died. Restarted after a few minutes and drove to a safe parking location where it now resides. Will no longer start.

Clearly the distributor cap/rotor wasn't the root cause, though replacing them did seem to improve things significantly.

[fredjacksonsan]

If your cap and rotor were bad,then your spark plugs probably need to be replaced also. And if your plug wires are old, replace them too.