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Unread 10-05-2010, 10:43 AM   #1
janderson79
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Starting Issues - 2001 Cherokee Sport

Hey guys,

I have a 2001 Cherokee Sport with 120k on it. It has always been a great vehicle with minor problems. The other day I was driving on the highway when it just stalled out on me. I pulled over and cranked and it started fine. I drove about 50 yards and it stalled again. Wouldn't start again. I waited about 10 mins or so, cranked the engine and it started. Went about 30 feet and it stalled again. By this time I was on a hill and couldn't get it to start. If I waited 5-10 mins it would fire up but not for long before it died again. Towed it home to the driveway. I have gone out several times since and if it has been sitting for a little bit the engine will fire up but will stall within 10 secs - 30 secs later. Seem like a fuel delivery problem to me but wanted your thoughts about what to check first. Should I get a fuel pressure gauge and check that first?

I searched the forums and found plenty of likely fixes for my problem but couldn't find one that ever mentioned if I let it sit then it will start but if i try to keep starting it after it has already stalled it won't.

Thank you for any comments and help.

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Unread 10-05-2010, 11:30 AM   #2
CJ7-Tim
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Test the CPS. Next, test the fuel pressure at the fuel rail. You should have 49psi +/- 5 psi when running.


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.

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.

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. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU may behave oddly until you remedy this.



Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- 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.

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.


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


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 displays correctly and/or the No-Bus is gone, replace the CPS.

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.

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.


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.


The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector may be on the passenger side, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.

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If this information has been helpful, please click on the "thumbs up" icon on the bottom right side of this section.


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Unread 10-05-2010, 11:31 AM   #3
tjwalker
It's the crank sensor!
 
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Agree that the crankshaft position sensor is the "primary" suspect here.
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Unread 10-05-2010, 12:56 PM   #4
dukie564
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Yup almost definitely the CPS

BTW great writeup Tim!
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Unread 11-13-2010, 07:00 PM   #5
Drecar
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hoping for help, help!!!

i also have 2001 xj sport. there have been misfires over last 2 years. i discovered it was related to gas, e10.

last week cel comes on. cleaned air filter no change. replace spark plugs reset cel. next day driving jeep is loosing power and feels like it is not responding to gas pedal being pushed. vibration in stick shift. towed to shop. mechanic advises to replace coil rail. he also changes 2 rear o2 sensors and all fluids and cleans engine compartment. next day cil comes on instantly on start with sputtering white smoke from exhaust. replace tps and iac now sputtering with black smoke at exhaust. code on reader still saying tps.

what the hell is going on?
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2001 Cherokee Sport 2dr manual
RE 3.5 SF w/Full Leafs, Track Bar, AA SYE CV Shaft
JCR Front Pre Runner, Rear Bumper and Two Rock Sliders
BFG AT For the Street and BFG MT For the Trail
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Unread 11-13-2010, 08:26 PM   #6
CJ7-Tim
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Quote:
Originally Posted by Drecar View Post
....last week CEL comes on.....
Without the exact Check Engine Light codes that were downloaded, all anybody can do is guess at the true cause.

Stop by the auto parts store and download the CEL codes. Write down the exact code numbers and post them here.
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Unread 11-14-2010, 07:03 AM   #7
tjwalker
It's the crank sensor!
 
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Yup, must have the exact code numbers posted here in order for us to help you.

The OBD system and the associated check engine light and codes on your Jeep is extremely valuable in isolating root cause of your problems.
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Unread 11-15-2010, 06:12 PM   #8
Drecar
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P0123

thanks fellas.

the exact code is P0123.

is it possible to mix up 02 sensor parts? i noticed that i have 3 different part numbers. the mechanic said he change the 2 in the back and showed me the harness only fits one way and cant be mixed up.
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2001 Cherokee Sport 2dr manual
RE 3.5 SF w/Full Leafs, Track Bar, AA SYE CV Shaft
JCR Front Pre Runner, Rear Bumper and Two Rock Sliders
BFG AT For the Street and BFG MT For the Trail
Mobile One Synthetic 10w 30 High Mileage
Surco Roof Rack, Garmin 60Cx, Winch
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Unread 11-16-2010, 12:59 PM   #9
Drecar
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so i spent hours searching to provide guidance to my mechanic on the issue before he tells me to replace pcm with i know isnt required now.

does tracking down a ground fault, looking for moisture or a bad connections, check clockspring, fuel pressure, crankshaft and camshaft sensor sound like the prudent course of action. several threads are asking for help but rarely is there a follow up as to what solved the problem. sadly im realizing that the art of automotive diagnostics is being replaced by part changers.
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2001 Cherokee Sport 2dr manual
RE 3.5 SF w/Full Leafs, Track Bar, AA SYE CV Shaft
JCR Front Pre Runner, Rear Bumper and Two Rock Sliders
BFG AT For the Street and BFG MT For the Trail
Mobile One Synthetic 10w 30 High Mileage
Surco Roof Rack, Garmin 60Cx, Winch
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Unread 11-16-2010, 02:21 PM   #10
CJ7-Tim
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Quote:
Originally Posted by Drecar View Post
so i spent hours searching to provide guidance to my mechanic

First, search for new mechanic, the current one is a moron (and lazy).

P0123 (M)Throttle Position Sensor Voltage High. Throttle position sensor input above the maximum acceptable voltage.

Inspect the wires and wire connector at the TPS, if that checks out, stop by the dealership or NAPA and get a new Throttle Position Sensor. Cheap engine sensors are cheap for a reason, they are poorly made and can be defective right out of the box. I only use JEEP sensors on my Cherokees.
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Between 2009 when Obama took office, and 2013, median annual household incomes have fallen by more than $2,100.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ......

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
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Unread 11-16-2010, 04:54 PM   #11
Drecar
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changed tps and iac, no change.
__________________
2001 Cherokee Sport 2dr manual
RE 3.5 SF w/Full Leafs, Track Bar, AA SYE CV Shaft
JCR Front Pre Runner, Rear Bumper and Two Rock Sliders
BFG AT For the Street and BFG MT For the Trail
Mobile One Synthetic 10w 30 High Mileage
Surco Roof Rack, Garmin 60Cx, Winch
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Unread 11-20-2010, 03:42 PM   #12
Drecar
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so apparently the issue resolved itself, hmmm. but it has never run smoother. unfortuately now i need a clutch.
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2001 Cherokee Sport 2dr manual
RE 3.5 SF w/Full Leafs, Track Bar, AA SYE CV Shaft
JCR Front Pre Runner, Rear Bumper and Two Rock Sliders
BFG AT For the Street and BFG MT For the Trail
Mobile One Synthetic 10w 30 High Mileage
Surco Roof Rack, Garmin 60Cx, Winch
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Unread 11-20-2010, 05:23 PM   #13
tjwalker
It's the crank sensor!
 
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If your engine runs fine after replacing the throttle position sensor and the P0123 code (TPS related) doesn't return, the odds are high that the new TPS fixed your problem.
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Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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