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Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > XJ Cherokee Technical Forum > 98 Cherokee 4.0L: no spark, coil tests good.

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Unread 11-18-2009, 10:36 PM   #1
cocheeze
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98 Cherokee 4.0L: no spark, coil tests good.

I am working on a friends 1998 Jeep Cherokee 4wd 4.0L 6cyl FI, and I am getting absolutely no spark whatsoever. I have removed multiple spark plugs and held them against the block to test for spark while someone cranks the engine, no spark. I have taken the coil wire off at the coil, and held it close to the terminal while someone cranks the engine, no arcing.

I assumed it was the coil, so i removed and tested the coil and it is fine. I also put in a new one just in case, no spark.

What else could it be? The only thing i could think of was maybe the ignition control module (or whatever this distributor has in place of points), but none of the local parts stores (autozone, schucks, baxters, napa, etc.) show an ignition control module in their systems.

Does anybody have any idea what might be causing this?

Thanks in advance for any help!

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Unread 11-18-2009, 11:09 PM   #2
CherokeeGT
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crank position sensor could be the problem
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Unread 11-18-2009, 11:11 PM   #3
xlr84fun
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my guess would be cps... I THINK... lol someone else will back me up or smash my hopes and dreams of being knowlegable... lmao
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Unread 11-18-2009, 11:13 PM   #4
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good thing you dont have renix , thats a ***** if you want to replace the cps
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Unread 11-19-2009, 12:02 AM   #5
cocheeze
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thanks for the info, guys!

i will try that next. hopefully they aren't too expensive.

she told me one day it just stopped starting mysteriously. does that sound consistent with the cps failing?

XLR84FUN - by cps, you mean crank position sensor and not cam position sensor, right?

HUSSLER737 - i have no idea what a renix is... is it some kind of electronic ignition or something?
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Unread 11-19-2009, 01:08 AM   #6
xlr84fun
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ya crank, not cam, sorry lol
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Unread 11-19-2009, 02:59 AM   #7
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Quote:
Originally Posted by cocheeze View Post
...... hopefully they aren't too expensive........

she told me one day it just stopped starting mysteriously
Troubleshoot and test, before you buy new parts.

The CPS is the most common failure, but not the only one that can cause a no-start.



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 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 08:02 PM..
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Unread 11-19-2009, 05:08 AM   #8
cocheeze
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wow, thanks man!

i doubt if i have ever seen a more thorough/helpful post in all my years of automotive forum surfing.

i will do the steps outlined tomorrow and get back to you guys with my findings.

using this forum has made me want to own a jeep!

thanks!

casey
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Unread 11-25-2009, 10:03 AM   #9
vettesandjeeps
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Different plug - what is terminal a for?

I also have a 98 cherokee, it is a limited 4.0l 4wd. Just died while driving, code reader showed P0320 and P1391, after reset and crank it showed only P0320. The 1391 indicates camshaft or crankshaft intermittent failure. Check engine light is not on, and was never on.

I am testing the CPS (crank) - but my plug is slightly different that what is shown above - it is completely oval. When I test what I think is b/c I get no resistance. When I test a/b I get infinite resistance. BUT - there is no way for me to know if I am really testing a/b or b/c because they are not labelled and the plug is completely symmetrical.

Anyone can offer up some help?

Anyone know how to test the Cam sensor?

Thanks in advance!
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Unread 11-25-2009, 10:44 AM   #10
mhall02
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Quote:
Originally Posted by cocheeze View Post
she told me one day it just stopped starting mysteriously. does that sound consistent with the cps failing?

That is exactly what mine did, no prior symptoms, just went out to the driveway one morning and it just cranked and cranked, but no startup. No codes detected with my code reader, fuel at the fuel rail, so I 'threw' ~$85 into a new crankshaft position sensor (since I read on this forum the symptoms and they are common no-start problems), replaced it and it started right up.

Did you replace it yet?
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Unread 11-25-2009, 01:38 PM   #11
CJ7-Tim
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Quote:
Originally Posted by vettesandjeeps View Post
..... Just died while driving, code reader showed P0320 and P1391....

..... there is no way for me to know if I am really testing a/b or b/c because they are not labeled and the plug is completely symmetrical.

Anyone know how to test the Cam sensor?

Your CKP/CPS Crankshaft Position Sensor will fail at some point after about 100,000-150,000 miles. I have had 5 1997-2001 Cherokees and 3 of them needed a new CPS. Re-read the Tech I posted, there are several indicators or symptoms that confirm a failed CPS. You can't go wrong buying a new genuine JEEP CPS. I would rather change the CPS in my driveway on a Saturday than beside a busy roadway on a cold, dark, and rainy Saturday night.


.
Camshaft Position Sensor


The Camshaft Position Sensor is located in the distributor on all engines.

For this test, an analog (non-digital) voltmeter is needed. Do not remove the distributor connector from the distributor. Using small paper clips, insert them into the backside of the distributor wire harness connector to make contact with the terminals. Be sure that the connector is not damaged when inserting the paper clips. Attach voltmeter leads to these paper clips.
1. Connect the positive (+) voltmeter lead into the sensor output wire. This is at done the distributor wire harness connector.
2. Connect the negative (-) voltmeter lead into the ground wire.
3. Set the voltmeter to the 15 Volt DC scale.
4. Remove distributor cap from distributor (two screws). Rotate (crank) the engine until the distributor rotor is approximately in the 11 o'clock position. The movable pulse ring should now be within the sensor pickup.
5. Turn ignition key to ON position. Voltmeter should read approximately 5.0 volts.
6. If voltage is not present, check the voltmeter leads for a good connection.
7. If voltage is still not present, check for voltage at the supply wire.
8. If 5 volts is not present at supply wire, check for voltage at PCM 32-way connector (cavity A-17). Leave the PCM connector connected for this test.
9. If voltage is still not present, perform vehicle test using the DRB scan tool.
10. If voltage is present at cavity A-17, but not at the supply wire:
a. Check continuity between the supply wire. This is checked between the distributor connector and cavity A-17 at the PCM. If continuity is not present, repair the harness as necessary.
b. Check for continuity between the camshaft position sensor output wire and cavity A-18 at the PCM. If continuity is not present, repair the harness as necessary.
c. Check for continuity between the ground circuit wire at the distributor connector and ground. If continuity is not present, repair the harness as necessary.
11. While observing the voltmeter, crank the engine with ignition switch. The voltmeter needle should fluctuate between 0 and 5 volts while the engine is cranking. This verifies that the camshaft position sensor in the distributor is operating properly and a sync pulse signal is being generated. If sync pulse signal is not present, replacement of the camshaft position sensor is necessary.
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Unread 11-25-2009, 02:00 PM   #12
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My daughter's cks went out at 100,000. no warning, went from running perfect to no spark, lucky it was in the driveway. I went with an oem sensor, read many posts saying aftermarket are not reliable, to me the price difference wasn't worth the chance of having it go out again who knows where or when.

Last edited by oldfamilyguy; 11-25-2009 at 02:01 PM.. Reason: omission
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Unread 11-25-2009, 02:12 PM   #13
vettesandjeeps
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CPS fixed it

I went ahead and threw in a crank position sensor, jeep has 141k so I took Tim's advice. Camshaft sensor tested out ok.

It then started right up. Still confused though - I have no way to tell what a b or c are on the plug, but - the new one had resistance of about 5k between what I think is b and c, and infinite resistance (open circuit) on what I think are a and b. I put it in anyway and it worked.

Most posts I found indicated the 0320 code as crank sensor and 0340 as camshaft sensor, I only had 0320, another reason I thought it would be a safe $100 to spend.

I'm really impressed with the quality and speed of responses, thanks guys. Hopefully you will not hear from me for a while - but I'll hang out and hopefully be able to answer some of the other questions out there.
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Unread 11-25-2009, 02:15 PM   #14
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One other note, I read some posts that indicate the camshaft sensor only affects fuel delivery and not a no spark condition. Not sure if anyone can confirm... knowing that would have saved me some diagnosis time. I also read this only applies to newer (98 on up?). Anyway, thought I would throw it out there in hopes someone can confirm and save someone else in my position some time later.

Thanks again!
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Unread 02-12-2011, 04:30 PM   #15
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Great thread!
I've been having this problem off and on for ... years with my 1989 (Renix)

I tested the resistance - right about 200 Ohm, then the Vac... looks like 0.1v,
However, my meter only has 200v, or 750v on AC. does it need to be on AC? (at < 1 volt, or only 1 impulse per revolution does it matter?) would DC be more accurate? (at 20v scale?)


Thanks for posting the info!!
BTW your diagram seems like a post-Renix, my 1989 only has 2 pins (in a 3-pin socket) ... so I may be testing it wrong????
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