Jeep WJ 4.0 Problem

[Grim]

great , thanks , ill have to check it out

 

[RockMonkey]

I managed to get the CPS plugged in all the way until it clicked. I took it for a spin to see if anything would happen. It drove fine for about 30 minutes, then just shut off. I tried jiggling/compressing the CPS plug, and that didn't seem to make any immediate difference. After a few minutes it started up, and I was able to drive a few minutes. Since I managed to get myself quite a ways from home, I had to go through this cycle several times. It shut off, nothing I do seems to help, but after a while it starts and runs for a few minutes.

I did notice that during the times when I can't start it, I can hear the fuel pump when I turn on the key just like normal. Also if I drain the fuel pressure at the fuel rail, then try to start it, and it doesn't start, there is more fuel at the fuel rail. None of this seems to point to the fuel pump as the problem, but I haven't been able to check the pressure yet.

I guess tomorrow I'll try to get a CPS from the dealer. I wish I didn't have to drive it for so long for the problem to show up...

 

[JoeT]

Have you pulled the codes to see if there was anything there?

 

[RockMonkey]

Have you pulled the codes to see if there was anything there?

The check engine light has never come on, so I assume there are no codes. I guess I could be wrong though. I just bought a CPS and a fuel pressure tester. I'm going to change the CPS this afternoon and see what happens. If I still have trouble I'll hook up the pressure tester and see if the fuel pressure changes before/when it won't run.

 

[RockMonkey]

I just replaced the crank position sensor, and it's been idling nicely for the last 15 minutes or so. For future reference, take the 8 bolts out of the transmission crossmember and drop the transmission down to replace the CPS. It makes it really easy to get to.

I also took a fuel pressure reading. It was right at 50 PSI. Anyone know off the top of their head what pressure a 2001 Grand Cherokee 4.0 should have at the fuel rail?

I guess I'll go drive around for the next 30 minutes and see if anything happens.

 

[RockMonkey]

I drove it around for about 90 minutes with no problems. It looks like it was probably the CPS. Chicky is taking it to Park City on Monday, so hopefully it's fixed.

 

[Grim]

thanks for all the great info , i was looking at mine lastnight and thinking about pulling the starter and droping the tranny a little to get to it. now to go pick up a new CPS.

 

[waynehartwig]

I had a CPS act like that on my 4.0L XJ. In fact it was NEW one from Autozone.

Exactly why I won't buy sensors from anywhere but the dealer. They aren't that much more, and you know they are good. However, sometimes the sensors at Autozone/Kragen are OEM sensors, just reboxed...


Does the WJ and say 04 Rubicon have them same CPS? I have the one off my old motor you can have for shipping...?

 

[RockMonkey]

FWIW I paid more than double at the dealer. It's well worth it if it lasts another 130,000 miles.

Just went to Costco and back with no issues.

 

[Grim]

i pick up a cps this morn (napa), after looking closer , my cps is on the driver side bellhousing. (03' 4.0) ill have to drop the tranny a little to get to it

 

[RockMonkey]

i pick up a cps this morn (napa), after looking closer , my cps is on the driver side bellhousing. (03' 4.0) ill have to drop the tranny a little to get to it

Yup, that's where they are. They're easy to swap once the transmission is lowered a bit.

 

[Grim]

got her swaped out last night , drove around the block a few times , drove nice , waiting to here from the wife if there is any difference .