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Unread 02-29-2012, 07:28 PM   #1
AnthonyZ28
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1993 XJ Cherokee 
 
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Location: Hallettsville, Texas
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Engine turns over, but won't start.

Today at school I got in my jeep, (93' cherokee sport, I6, 5 speed manual) turned the key and the engine turned over but didn't start. After trying a little more I got it started and seemed fine. So I drove it off the school property and was turning onto the main road ruuning through our town. When I did so it almost stalled but managed to save it. I went on a little more and as I was driving and the thing just died on me while driving. (3rd gear about 2200rpms) When that happened the motor went out along with the power steering but all electronics stayed on. I luckily managed to roll safely into a car wash where I parked by the vacums. There it did the exact same thing as it did at school, turned over but wouldn't start. My friend managed to get it started again. When he did, he was giving it some gas in neutral and it backfired and died again. I got back in tried a few more times unsuccesfully, I eventually got I started and took it to the nearest mechanic where it sits now. That time it seemed to run fine.



Not quite sure what the problem is. I drove it this morning and it behaved just fine. It's completly random when it does start. If any more info is needed, please say something.

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Unread 02-29-2012, 07:34 PM   #2
CJ7-Tim
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There are a few common Cherokee issues that would cause stalling/not starting. A failed Crankshaft Position Sensor (CPS) should be your first suspect.
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Unread 02-29-2012, 09:40 PM   #3
AnthonyZ28
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Quote:
Originally Posted by CJ7-Tim View Post
There are a few common Cherokee issues that would cause stalling/not starting. A failed Crankshaft Position Sensor (CPS) should be your first suspect.
Hopefully. If not what else could it be? Fuel pump possibly?
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Unread 03-01-2012, 09:06 AM   #4
CJ7-Tim
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Start with the cheap and easy solutions. Focus on common Cherokee failures. Test the components and systems before you buy new parts. Throwing random new parts at an unidentified problem gets expensive.

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.
- 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 03-01-2012, 10:06 AM   #5
jeepnphreak
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I would just replace the CPS on you jeep if you have not ever... when it goes your stuck.
Its super easy to replace. If you have small hands or a girl friend that is willing to get dirty, you can replace it with out drooping the tranny. I hade to pull the cross member and let the tranny droop about an inch or two to get my paws up in there.

A QUICK TIP.

remove the top (upper most) bolt first. Then the lower bolt.

put in place the new CPS and put in the LOWER bolt first. then the upper bolt.

it keeps the possibility of droping a bolt inside the bell housing low. If you drop something in the bellhouseing you have to pull the trasmision to get it out.
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Unread 04-04-2012, 10:49 AM   #6
Haus_XJ
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How do you get the 2 bolts out on the CPS? i can't figure out a way to get any tool i have up from underneath.. any recommendations?

My jeep won't start either. I haven't had much time, but here is what i've gone through so far:

1. I have new plugs, fairly new wires/coil/rotor.
2. I have fuel and can hear the fuel pump prime when i turn the ignition
3. I pulled a plug and do see a fairly dull spark. i'm not sure what to expect, but i did see spark.
4. I cleaned off the battery terminals. I am reading 12.0 volts on my scan guage.
5. I am going to try testing out the CPS, but i bought one anyways just in case it needs to be replaced. I don't have a voltmeter but i am going to unplug the CPS at the top as described above.

I'm going to have a hack at this again tonight (11pm) after work.. hopefully i can figure it out!

Oh yeah, i also have new rebuilt fuel injectors, but maybe my fuel filter needs replaced? i guess if i have spark it is a fuel issue?
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Unread 04-04-2012, 11:20 AM   #7
CJ7-Tim
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The spark should be blue and snap. If you see a yellow or orange spark, suspect your tune-up parts or coil.

CPS bolts can be accessed by removing the front drive shaft or by using 2-3 feet of socket wrench extensions and a wobble adapter. A helper under the hood to guide your socket, will also speed things up.

97-01 fuel filters are not routinely serviced unless fuel pressure/flow testing shows a blockage.
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Unread 04-05-2012, 01:11 AM   #8
Haus_XJ
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I'll have to check the spark later today (Thursday) when i have some help.

I replaced the ignition coil tonight, examined the cap and rotor. Everything looks good. Still no luck. Could the CPS still be the issue? i'm holding off on that because it is a more expensive part compared to everything else i've done so far.

I suppose the best solution would be to pick up an ohmeter so i can follow the instructions above.
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Unread 04-28-2013, 04:55 PM   #9
mysnocat
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not sure

If you are getting spark, does that eliminate the CPS as a possible source of the no start?
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Unread 04-28-2013, 06:38 PM   #10
CJ7-Tim
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Testing the CPS will show if it is failed, or not.
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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 problem; Government is the problem.
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Unread 04-28-2013, 07:30 PM   #11
mysnocat
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You listed "no spark" as a typical symptom of a bad CPS, but if I understand your response to my post, you can have spark and still have a bad CPS. I will go ahead and try your testing regimen. Thanks.

-------------

Well, resistance between terminals B and C was 656, so I will throw on my spare CPS tomorrow to try and resolve my own no start nightmare.

--------------

New CPS on and still no start.

Last edited by mysnocat; 04-29-2013 at 02:23 PM..
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Unread 07-10-2013, 01:26 PM   #12
azdude
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The car wash killed my XJ!

Any advice would be much appreciated. Please help!

1989 Jeep XJ 4.0 I6 died while going through a car wash a week ago so I believe the cause was water related. It will turn over but will not start. Here is what I have tried so far:

- fuel pressure consistent at 40 psi while attempting to start
- replaced CPS (not fun by the way), no change in symptoms
- took distributor apart to allow it to dry in case it got wet
- getting blue spark from ignition coil to distributor
- spark at plugs appears more white or yellow
- when starter fluid is sprayed in the air intake, it will run very rough for a second or two
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