CPS? sob just died on me on i-state Dear Lord Please Help

On the way home tonite my XJ (2000, 158k on the clock) just randomly cut off (no fuel - still had electrical) at 70mph on the interstate. I pulled over, shut it down, and tried to crank - plenty of electric, no fuel. Can't hear fuel pump, but never could before either. Let it sit for 2-3 minutes - cranked again, started up like new - ran about 100 yards, died again...

Let it sit again for about 5 minutes - started again and ran all the way home (about 15 miles).

Shut it off it the drive way and the sob would not start again - Had to let it sit about 20 minutes, and what do you know, the mf started up - got it in the garage and shut it down - When it is cold, it starts up just fine.

By my searching this sounds like the CPS - any thoughts?? Never had a problem at all with this XJ since I've had it (over 20k)., other that an occasional stumble/rough idle at start up.

This is my DD and I rely on it desperately - any insight is greatly appreciated...

Thanx

Sounds like it, Go pick one up and swap it out.


If you haven't found this post....
http://www.naxja.org/forum/showthread.php?t=34676&highlight=removing+CPS

Sounds another one for the CPS...

Should test it first.

ok - two quick cps confirmations lead me to the garage - I went out and started it up - no problem. Cut it off, then wiggled the cps sensor wire, got nothing - just cranks and cranks...Gonna remove the cps and check the wire(s)...

thanks

Yep CPS if it just cranks and cranks had same problem

If wiggling the crank sensor wiring CREATES a no-start and you can replicate this, this could be a connection issue. Gotta look at simple "cause and effect" principle here.

I would test the crank sensor and also ensure that the connector/wiring is in good condition so that it's making good electrical contact. A bit of dielectric grease on the connector wouldn't be a bad idea.

Crankshaft Position Sensor: (CPS/CKP) Failure Symptoms / Testing

*Both the fuel gauge and or voltage gauge may not work/display

*It is possible that you may see a No Bus on the odometer (on newer models only)

*You will have no spark. Fuel pressure may check out okay at the fuel rail, but fuel won’t get to the fuel injectors

*For 96 + newer, sometimes the OBDII code reader has trouble connecting to /reading codes. Crankshaft position sensor failure may or may not result in a check engine light/fault code.

*Crankshaft position sensors can be intermittent resulting in an abrupt misfire.

* "Thermal failure" is common. Thermal fail means that the sensor fails when engine gets hot, but works again when engine cools down. Be aware of this when testing, as if you have a sensor that suffers from thermal failure, it’s possible that it may test GOOD as soon as it cools down.
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CRANKSHAFT SENSOR TESTING PROCEDURE: 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.

2. Place an ohmmeter across terminals B and C. The terminals are identified as A-B-C looking into connector from left to right with the "notch" in the middle of the connector on your right. Ohmmeter should be set to 1K-to-10K scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if LOW RESISTANCE

Hi,
I would put serious money on it being the CPS, my 93 XJ would drive 2 or 3 miles and then cut out, after 15 to 20 minutes it would start back up good as new, till the next time it cut out. A new CPS fixed it and it's been running great for a couple of years now. I eventually figured out what happens - the CPS is fitted to the top of the bell housing and gets it's impulses from the flywheel, as the engine warms up the bell housing expands and moves the CPS away from the flywheel, this results in the computer losing the CPS signal and the engine quits, it will start back up when the bell housing cools back down, a new CPS can handle this expansion but an old one cannot. If you do change the CPS make sure you zip tie the CPS lead to the firewall to keep it well away from the exhaust.

I had a similar issue with my previous XJ. The earliest signs of trouble were kind of interesting. If I charged through a puddle, the Jeep would stall instantly, then start a few minutes later. If I slowly drove through water but didn't splash a lot, no issue. Eventually, right after I replaced the internal slave cylinder as a separate issue, it drove for a few miles, then dropped dead in a driveway. Turned out that the CPS wires had lost their insulation due to being too close to the engine--it just burned off. My girlfriend suggested the CPS, and then I replaced it. No more stalling in water crossings after that, and the Jeep ran again.

I checked the fuel pressure first visually by pressing on the valve on the fuel rail and watching the fuel spurt out, then with a pressure gauge at the same point. I also determined I had no spark first. One needs very skinny arms, but the CPS can be removed from the top by reaching between the firewall and the block and contorting one's arms in uncomfortable ways. My girlfriend actually did that part since my arms didn't fit!

--wp11

Turns out it was not the CPS after all.

In doing some extra trouble shooting after the CPS tested ok, my mechanic friend found a frayed wire going to the fuel pump. He replaced the wire, and bingo, :sunshine:I'm back in business.

Thanks to all for your input. Even the mech thought CPS...

Sleepy, are you going to LBL with the southeast group this weekend? There are quite a few of us going. Should be a good time.

Sleepydog said:

Turns out it was not the CPS after all.

In doing some extra trouble shooting after the CPS tested ok, my mechanic friend found a frayed wire going to the fuel pump. He replaced the wire, and bingo, :sunshine:I'm back in business.

Thanks to all for your input. Even the mech thought CPS...

Click to expand...

Good deal! Sometimes XTRA troubleshooting is better than pitching parts at the heep. Thanks for the feedback.

:clap:

Mbogosia - I would love to, but I've got a sick kid - gots to stay close to home...Sounds like fun though...Thanks...

Thats cool. Good to have your priorities straight.