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Unread 12-09-2009, 04:39 PM   #1
speeddemon651
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Ignition problem, Please HELP !!!

1998 Jeep cherokee 4.0 litre, 67,000 miles. Jeep has just had its spark plugs replaced, wires, distributor cap and rotor. Everything was running great, had the jeep idling infront of the house and it just died. Sounded like it hit a bad shot of gas and cut off. I cranked it over and started right up and ran fine for a few more minutes, then cut off again. I started it up again drove it down the street and on the way back it cut off again. Barely got it back in the driveway and now can't get it to start.

At first i was convinced it was water in the fuel, pulled the injector rail off, blew it out, drained the entire gas tank and put 5 gallons of 93 back in it and it still wont start.

I started checking plugs, everything looks fine, checked for spark at the plugs and there was none. Pulled the coil to distributor wire off and using needle nose in the end that plugs to the top of the distributor while cranking it over I would see a speratic spark once or twice a minute holding it with in a 1/4 away from the pin I pulled it off of.

At that point figured it must be the coil, pulled it off and replaced it and the jeep is still doing the same thing, not getting spark. I have not replaced the distributor electronic points yet, but they look fine though, checked the distributor cap and rotor again and they look fine.

Does anyone have any idea what this might be ? possibly the electronic points in the distributor ?? I checked the sprak plug wires and they look fine also, no burn spots and have less then a 100 miles on them from autozone.

Spark plug wires, plugs, distributor cap, rotor and coil are all brand new, ANY IDEAS ?? is there anyone ignition module that could go bad somewhere ? thanks JH

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Unread 12-09-2009, 05:03 PM   #2
PepperRedXJ
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If you've gone that far with replacing ignition parts I'd be hesitant to believe that it still IS an ignition problem..

My next guess would be to test the fuel pressure at the rail, then turn it on and watch for any drops in pressure..
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Unread 12-09-2009, 05:11 PM   #3
speeddemon651
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plenty of fuel pressure, pump runs good. It is a ignition problem forsure. I'm only getting a spark speraticly once or twice a minute. only thing else I can replace is the electronic points in the distributor other than that I'm not sure if it has a ignition module somewhere that could be going bad ???



Other then the Ignition pickup in the distributor not sure what else it could be.

Last edited by speeddemon651; 12-09-2009 at 05:31 PM..
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Unread 12-09-2009, 06:55 PM   #4
pentastar01
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Crankshaft position sensor would be my next move. That little bugger tells the PCM where the crank is at and if it doesn't know how can it fire properly. Also it can't hurt to perform the "wiggle" test.
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Unread 12-09-2009, 09:32 PM   #5
speeddemon651
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I went to autozone.com and looked up ignition for this thing and that was the second thing I found that could have went bad
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Unread 12-10-2009, 03:55 AM   #6
CJ7-Tim
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Testing the CPS is easy enough.


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 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, 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. 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)



.


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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Last edited by CJ7-Tim; 05-15-2010 at 08:59 PM..
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Unread 12-10-2009, 10:29 AM   #7
98muddyjeep
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if you do have to replace the cps if you remove the front driveshaft it will make things go much eaiser,I just did mine and that made it very easy.
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Unread 12-10-2009, 10:56 AM   #8
rollz4kix
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I'd shoot right at the cps. that thing can be a real pain.even when you test it it'll lie to ya.I found a 1/4" ratchet with a 3" extension will do the trick (bring a little 2" one underneath there with ya just in case) ,just gotta contort them arm's a little bit and use the mind's eye....HAVE FUN ...
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Unread 12-15-2009, 11:37 AM   #9
speeddemon651
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thanks for all the help guys, going to try that tonight.
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