2000 Grand Cherokee turns over but will not start

[jrandallc]

2000 Grand Cherokee Laredo
4.0 Inline 6

All of a sudden, my Jeep will turn over but will not start. Pretty much an overnight problem, but I've been off most of the past week and haven't driven it much. If I try to jump it off, that doesn't help at all. I've listened for the fuel pump to whine, and that is fine.

From other things I've read, a lot of fingers get pointed at the Crankshaft Position Sensor. Is there a way to test this sensor before I make the effort to replace it? Other ideas on the problem?

[fredjacksonsan]

What codes are you getting? A google search will find the trouble code for you, once you have it. To get the code, cycle the ignition switch on/off/on/off/on within 5 seconds and the code or codes will flash on the mileage display.

It does sound like the CPS. If that's what it turns out to be, then check the Cherokee forum as there are numerous "how to" threads to install your own.

[jrandallc]

Thanks for the reply. I checked the codes (didn't know that trick before) and it's throwing P1594 (charging system voltage is too high) and P0320 (crankshaft position sensor (CKP)/engine speed (RPM) sensor-circuit malfunction). If there is indeed a problem with the CPS, would that naturally throw a code on the voltage too high? I've bought a new CPS and will try to replace it then update.

[fredjacksonsan]

Hey, you're welcome. I'm not on here much anymore but check in when I can.

High voltage might indicate several things, but I would check the battery and cables first.

A bad battery can force the alternator to work harder than normal and put out excessive voltage.

Corroded cables can do the same - I've personally seen, and there have been many vehicles on here, that had corroded (usually positive) battery cables which were increasing resistance or stopping electrical flow completely. Make sure to peel back the insulation a bit if you see anything....I've seen corrosion as far away from the battery as 8".


I'd replace the CPS then see how things are doing...shouldn't take too long to have a close look @ the cables and have the btty tested @ Advance Auto or somewhere.

[jrandallc]

I pulled the neg on the battery to reset the codes (all battery terminals seemed fine) and checked the codes again and was only getting the 0320 for the bad CPS. I replaced the sensor and all is well now. Checked for codes again when I was done just to be sure and none were being generated. I tried to jump the Jeep off when I first had trouble. That may be what generated the electrical code.

Just for reference on the Crankshaft Position Sensor, I replaced if without dropping the crossmember. I used extensions (12", 3" and 5") and an 11mm socket to reach it from above the tranny case. Loosening it wasn't that tough. Actually pulling the sensor out of its hole was the hardest part, and had a little trouble getting it back in.

I guess the only thing lingering from this job is this: there was a small metal cover attached to the old sensor. I couldn't figure out exactly how it went back on and exactly what it covered. Anyone have an idea on that? How critical is it that it goes back on? If I'm under there again, I may try again at putting it on. Once the sensor has been in place for a little while, it will hold still while I try to put the screw and the metal cover back into place. With a new, loose sensor, it just didn't seem worth fighting over today.

[fredjacksonsan]

Glad you're back on the road! I used a lot of extensions to get to mine also. I'd seen where some folks were able to get to it from the engine compartment...they must have had tiny hands.

The metal cover ... on my 00, I couldn't get it back on either, and never had an issue. IMO the cover is to help protect the wiring, but it's at such a protected place already. If/when you go back in, try putting a little grease between the cover and the sensor to hold them in place. It's a bear to reach back up in there.