Questions and Answers

Jeep Cherokee Laredo No Start Q. Mr. Ciulla, I wasn't 100% sure if this was the way to get in touch with you, but better this way than no way. :) I have a 1990 Jeep Cherokee Laredo 4.0 liter 6 cylinder 4x4. Lately, either my car is begging for retirement, or just wants to be a PITA.

Several weeks ago, the car would not start. It would be days and the car would not start, so we got it towed to the mechanic. When it got there, it turned on. It's like the sucker knew we were out to fix it. Since the car started, what could we determine? And besides I don't like the mechanic much, but you know how fathers are with not changing things around.

Anyways, the car ran fine for a few weeks. Last week, it did not start again. (Both were the first time I tried to turn the car on those days). This time around, I had some friends' come over that were very good with cars. They ran tests to see if all the crucial electrical parts were pumping juice into the car. Everything tested out fine. So off to the mechanic it went again, but this time it did not start right away.

I had to go off to class, but when I went over there he got it running. According to him, all he did was play around with the second relay on the right side of the car (I'm horrible at cars), which from the diagrams that I got from other problems that you solved is the Fuel Pump Relay. No biggie I thought, and it ran good for a while longer.

Today was weird though, the car turned on fine. I went somewhere a few miles away (like 10), turned the car off for about 15 minutes, and then it wouldn't start. It never did that before, it was usually fine after it turned on the first time. After cranking it and bitching at it for 20 minutes, it turned on. I got home and it didn't turn on anymore. I'm about five minutes away from taking a baseball bat to the sucker. What do I do? (Besides find a new mechanic.)

Just for a bonus, so I don't bother you much more, my catalytic converter is broken. The problem is that it is not the first one I have put on it. I took it to a very good Muffler shop here in Miami, FL, and they told me it was melted (which I also saw that it was). The man at the shop told me that Cherokees get that problem a lot. But no one seems to know what the heck the problem is. Are you stumped too? Thanks for your time Mr. Ciulla; I hope you're able to help.

Sincerely,
Alex

P.S. Do you have any diagrams that show exactly where or what the relays go to

A. There were a number of problems with the Crankshaft Position Sensor (CPS) on the 4.0 liter engines. In fact a TSB was issued on the problem. A bad CPS would certainly cause the problems you indicate and may even explain why the catalytic converter melted down.

Here's a diagram of the relays in the area you described.