AdmiralSavage

Hello, I had a problem with my 2002 Jeep Grand Cherokee I6 where while driving it stalled and I had to let it roll to a stop and put it in park and try to turn it back on. It happened twice. First time the engine turned on right away, second time happened yesterday which was like a week after and this time when I tried to start the engine it would only crank like if it was out of gas even though I had a full gas tank. I kept trying and trying and it wouldn't turn on, sometimes it seemed like it turned on for a quick second but never did run. I tried using jumper cables from my dads toyota to my jeep and nothing, same thing. Called roadside assistance to tow since I didnt know the issue and he put his jumper box on it and it started right up. He said our cables were too thin and thats why we couldn't turn it on. Does anyone have any idea on what had happened, was it just coincidental that when he got there it turned on or did it need that extra surge of power to the battery? Also what did cause it to just shut off while driving randomly if anyone has any ideas. Thank you.

dave1123

Sounds like the symptoms of a failing Crank Sensor. They get hot and don't put out a signal, then cool down and start perfectly. I had mine actually restart itself while it was still rolling! Word to the wise, bite the bullet and buy Mopar! Most aftermarket ones are crap. If you have the 4.0, this is not something you'll want to do more than once!

AdmiralSavage

What are other symptoms or a failing crankshaft position sensor in case I have so it's easier to diagnose? Thank you!

ihscouts

This is what happened to me when I had the same problem. Could be a fuel pump connection or the fuel pump itself. I replaced a fuel pump and the new connector allowed water ingress where wires entered connector. It corroded the 12VDC+ post and began to overheat further degrading the electrical connection. The motor would shut off usually under load but was very random. Sometimes it would restart and others it wouldn't until cooled down, then start like nothing happened. Connector is near the inline fuel filter. X2 on getting a Mopar Crank Sensor, aftermarket generally use pretty weak magnets compared to the Mopar part. Huge PITA to change them out. I replaced the Crank Sensor when this problem happened and when the motor quit again I bought a Mopar sensor and obviously it quit again until I found the real problem. The last instance of the motor quitting it wouldn't start at all. My son said he didn't hear the fuel pump when I turned the key or cranked the motor and that's when I crawled under the Jeep and found the bad pump connection. I'm an Industrial Electrician so it was easy to understand the problem when I put a light on the pins. Good luck, I know how frustrating it is.....

AdmiralSavage

Also I forgot to mention at high rpms let's say I'm in park and I rev to like 4k for a bit the cel will begin to flash for a bit. I ordered cam and crank sensors already btw. Mopar cam sensor and they didnt have mopar crank so I ordered the best I could find.

jeepdewd

Definitely try what this guy says but if it does not work you will have to take it to a mechanic to have your wire harnesses that go into the computer repinned unless you can do it yourself.

I had a "dying jeep" once. Started with your symptoms. I changed everything out and the issue kept coming back. Repinning the harnesses also found a couple of busted wires. My jeep ran great until about a month ago but now i have some internal motor issues. 300k on it now. The harness job will run you about 500. It's worth it if you like your jeep

AdmiralSavage

Hmm alright thanks, I'll mention it to my mechanic if it keeps coming back after changing those parts

dave1123

Just a word about the Mopar CPS. It's built around a neodymium magnet where most aftermarket ones aren't. Most others will stick to a screwdriver, but a Mopar one is strong enough to be lifted by one.

AdmiralSavage

It was the Crankshaft sensor. Had it replaced, the old one was in bad shape, the part the bolt goes through to secure it to the block was broken so it wasnt secure on the engine. No more problems now. Thank you guys for your advice.

Jpoer

I’m having a similar issue. The last time it died two days in a row. The shop could not duplicate the issue and couldn’t figure out what caused it. Good electrical. Good fuel pressure. It’s been a month without happening again but today it died. I found this thread. I tried it after it cooled down and no luck. I disconnected the battery and still no luck. I was going to get the sensor replaced but I can’t tell if that is the real issue. Ideas?