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Unread 07-02-2012, 06:02 PM   #1
conner65
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1997 XJ Cherokee 
 
Join Date: Mar 2012
Location: Nanoose Bay, British Columbia
Posts: 24
Shuts itself off

I was comming home from work yesterday and my truck ran fine for about 10 mins to the gas station, then after filling up about 2 minutes down the street it just shut itself off, no sputters no weird idling or anything like that, just died. I started it again and it started right up instantly and ran great it stalled on me 3 more times each a couple minutes apart. I finally called my dad to get a ride home. When he got there I started it up to show him what was happening and it ran for about 10 minutes so I decided to just try driving it back, I made it home without it dying anymore. Now it is doing the same thing today, runs fine for a couple minutes, then dies. Doesnt seem to make a difference if it is driving or just idling in the driveway, rpms doesnt seem to change it either. We cant find any loose wires or any that are grounding out anywhere, all the fuses are fine, battery is charged. Anyone have a problem like this?

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Unread 07-02-2012, 07:52 PM   #2
CJ7-Tim
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2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
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Probably a faulty CPS.

The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Typical Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- engine may randomly stall for no apparent reason
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds and the ECM/ECU may behave oddly until you remedy this.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.

If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.

Diagnostic steps to confirm the CPS is the cause of your no-start

1) You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now display correctly and/or the No-Bus is gone, replace the CPS.
2) If the CEL does not come on when the key is turned to the RUN position... then the CPS/CKP is bad.
3) Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is near the Transfer Case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.

CPS Testing

Crankshaft Position Sensor Connector (CPS/CKP)


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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 (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.


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Unread 07-03-2012, 03:19 PM   #3
conner65
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1997 XJ Cherokee 
 
Join Date: Mar 2012
Location: Nanoose Bay, British Columbia
Posts: 24
Thanks for the detailed reply, I'll try and get to it today. Also, for some reason the dome light inside the truck is staying on, I dunno if this is at all related to what's going on but all the doors are closed and the light wont go off.
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Unread 07-03-2012, 03:33 PM   #4
buildin1XJ
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1999 XJ Cherokee 
 
Join Date: Oct 2011
Location: Knoxville, Tn.
Posts: 1,581
X1 on Tims post, the man simply put knows XJ's BIG TIME.
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Unread 07-04-2012, 01:56 AM   #5
Reptile
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1991 XJ Cherokee 
 
Join Date: Feb 2011
Location: Bakersfield, CA
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Quote:
Originally Posted by conner65 View Post
Also, for some reason the dome light inside the truck is staying on, I dunno if this is at all related to what's going on but all the doors are closed and the light wont go off.
Totally unrelated. You have sensors in each of the doors. It only takes one of them to be faulty for the lights to stay on... which you got to figure out which one. I know a fix that really isn't one, remove the bulbs. Works for me.

After you rule out the CPS, you might want to look at a fuel delivery issue. That's what happened when my fuel pump went on vacation... except then it would eventually decide not to start again right away. If this happen again and gets you stranded, you might try kicking the tank. Just keep that in mind, could be your ticket home.
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Unread 07-04-2012, 05:41 PM   #6
conner65
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1997 XJ Cherokee 
 
Join Date: Mar 2012
Location: Nanoose Bay, British Columbia
Posts: 24
It doesn't seem like the fuel pump, it doesnt sputter or anything, just shuts off. After all the research I've done it seems like its probably the CPS. Heres a video I got of it today. Skip to 1:50, I dont have editing software on my computer to cut all the extra **** out.
http://www.youtube.com/watch?v=AgrL3...e&noredirect=1
Also, a couple times after it has stalled it will not start, just cranks. Then after like 10 minutes or so it will start right up.
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Unread 07-08-2012, 11:57 PM   #7
Reptile
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1991 XJ Cherokee 
 
Join Date: Feb 2011
Location: Bakersfield, CA
Posts: 1,297
Quote:
Originally Posted by conner65 View Post
It doesn't seem like the fuel pump, it doesnt sputter or anything, just shuts off. After all the research I've done it seems like its probably the CPS. Heres a video I got of it today. Skip to 1:50, I dont have editing software on my computer to cut all the extra **** out.
http://www.youtube.com/watch?v=AgrL3...e&noredirect=1
Also, a couple times after it has stalled it will not start, just cranks. Then after like 10 minutes or so it will start right up.
Okay next time it cranks and won't start, you need to determine if you have spark (unplug a spark plug, make it touch the ground). No spark = CPS.

The fact that it doesn't sputter doesn't mean anything.
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Unread 07-09-2012, 08:31 AM   #8
p2y2r7o
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1997 XJ Cherokee 
 
Join Date: May 2007
Location: USA
Posts: 319
When I was having the same problem a couple years ago, I had over $800.00 of work done at a shop to try and fix it. After wasting all that money and time my jeep was still cutting itself off. After CJ7-Tim's same suggestion I spent about half an hour and replaced the CPS myself. It fixed the problem and i was kicking myself haha...If only I had known in the beginning.
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Unread 07-09-2012, 11:23 PM   #9
conner65
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1997 XJ Cherokee 
 
Join Date: Mar 2012
Location: Nanoose Bay, British Columbia
Posts: 24
Changed the CPS, works great now. Cost $175, with my discount too.
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ckp , cps , crankshaft sensor , random stalling , stalling

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