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  #1  
Old December 8th, 2007, 16:24
PhotographerMike's Avatar
PhotographerMike PhotographerMike is offline
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New CPS Needed w/'87-90 Harness Upgrade?

I just replaced the CPS in my wife's 1989 after doing Search and Research here.
Now it starts up and runs for a short time (under 5 minutes) and just shuts off.
Somewhere in my search I found a a reference to "Chrysler service bulletin 18-51-88" (Google it to find the PDF). The Cherokee has the upgrade already installed.

The bulletin says, in part;
Quote:
Source: Chrysler service bulletin 18-51-88
The symptoms described above could be caused by a weak signal from the CKP sensor. A new CKP sensor and harness is available to correct this problem. The new CKP sensor is available in a kit, part number 83100066. The kit includes the new CKP sensor, and a sensor patch harness for connecting the new sensor directly to the engine control module (ECM).
AND
7. Locate the old CKP sensor on the bellhousing. Remove the CKP sensor lead from the retaining clip. Remove the CKP sensor retaining bolts, and discard the CKP sensor.
Is this a different CPS sensor than the one I just bought at NAPA or am I having some other problems?

After the replacement I cleaned all the under hood connectors, battery conections and ground wires.

Thanks!
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  #2  
Old December 8th, 2007, 20:22
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Still won't keep running!

Got back from dinner, reached in the window, turned the key and started right it up.

No problems, well maybe a bit of rough idle at first, idles fine as it warms up.

5 ~10 minutes later, it just stops . . .
It won't start back up when warm.

Ideas?

Wrong CPS? Dirty flywheel? Bad karma?
What else acts like a failing CPS?
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  #3  
Old December 8th, 2007, 20:43
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Re: New CPS Needed w/'87-90 Harness Upgrade?

do a fuel pressure test.Maybe your pump is failing....or another thing to think about is you might have dirt in the bottom of your tank that clogs up the fuel pump and then when you shut it off the sediment drops back into the bottom of the tank.HTH
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  #4  
Old December 8th, 2007, 21:45
600dollarxj 600dollarxj is offline
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Re: New CPS Needed w/'87-90 Harness Upgrade?

It wouldnt be the crank position sensor, that is only used to start the car. (Or that's what I was under the impression of anyway)
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  #5  
Old December 8th, 2007, 21:57
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Re: New CPS Needed w/'87-90 Harness Upgrade?

no my understanding was it's used for timing. kind of like a crank trigger.

please correct me if I'm wrong
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  #6  
Old December 9th, 2007, 04:48
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Also... make certain that the harness is clear of the downpipe.
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  #7  
Old December 9th, 2007, 08:23
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Quote:
Originally Posted by 600dollarxj
It wouldnt be the crank position sensor, that is only used to start the car. (Or that's what I was under the impression of anyway)
No, the CPS is definitely integral in keeping the engine running. Often, a hot CPS will kill the engine.

One trick to try when the engine dies is to put water or ice down near the CPS to cool it off.

Mike...are you going to the Christmas party later today? All the great Jeep minds will be there.
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  #8  
Old December 9th, 2007, 11:37
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Re: New CPS Needed w/'87-90 Harness Upgrade?

On the inner drivers side fender there should be a white ceramic block w/ 2 orange wires going to it. Jumper those wires together and see if it will continue to run.
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  #9  
Old December 9th, 2007, 11:48
88xjlover 88xjlover is offline
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Re: New CPS Needed w/'87-90 Harness Upgrade?

After it dies and won't start again check for spark at the plugs. If there is strong spark it's not the ckp. Check for fuel problems. I have bought aftermarket parts that didn't work correctly. This is like a $25 part at the dealership, or maybe that was the tps.... can't remember, but that could be your problem as well. If the ckp didn't fix the problem then maybe you should start checking other sensors, ground wires, etc.
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  #10  
Old December 9th, 2007, 17:59
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Quote:
Originally Posted by xjohnnyc
. . Often, a hot CPS will kill the engine.

One trick to try when the engine dies is to put water or ice down near the CPS to cool it off.
I never would have thought to cool the CPS / CKS down.

Fired it up, let it run a few minutes while I read my Chiltons until it shut down. Tried to restart, nothing.
Checked the resistance and no reading (should be 125 ~ 275 Ohms).
Got out the long funnel for a better aim and added water to cool the CPS down, the reading came up to 230 Ohms.
Fired it up . . ran . . died . .
Again, fired it up . . ADDED a little stream fo WATER . . it kept running, until I stopped.
Did it several times for entertainment. (Sorry I couldn't make to the chapter party, I'm sure I'll read about it.)

So the New CPS is defective and needs to go back to NAPA?
The Old CPS reads 235 Ohms sitting here, I'll pop it in the toaster oven and see if its' resistance goes away with heat.

Any other ideas?
Do I need to get out the 4 foot extension again to replace the new CPS?

Slo-Sho,
I jumped the "white ceramic block". Thanks for the tip, but it didn't help.

Others,
I replaced the plugs and cleaned the ground wires, connections and contacts after I swapped the CPS.
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  #11  
Old December 10th, 2007, 12:23
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Hallo. What about the ignition coil? It can fail when hot!
greetings
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  #12  
Old December 10th, 2007, 13:16
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Quote:
Originally Posted by wim hoppenbrouwers
Hallo. What about the ignition coil? It can fail when hot!
greetings
And greetings back from Southern California!

True, but pouring water on the CPS for cooling kept it working. Water on the coil is not a good idea.

I put the original "failed" CPS in the oven to see how it would react to 200 F ( 100 C ) heating. Its' resistance went from 235 Ohms to 375 Ohms and spiked higher (700+) when I pinched the wires with my fingers.

It may "sound" like I know electronics, I DON'T. If anyone knows what a CPS should read, please let me know.
OR;
Am I on the wrong track with our stalling Cherokee?
Thanks again
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  #13  
Old December 10th, 2007, 15:05
89xj 89xj is offline
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Re: New CPS Needed w/'87-90 Harness Upgrade?

have you tried by passing/jumpering the ballast resistor?
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  #14  
Old December 10th, 2007, 15:12
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Re: New CPS Needed w/'87-90 Harness Upgrade?



You didn't read the whole thread now did ya?
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  #15  
Old December 11th, 2007, 08:48
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Re: New CPS Needed w/'87-90 Harness Upgrade?

Quote:
Originally Posted by wim hoppenbrouwers
Hallo. What about the ignition coil? It can fail when hot!
greetings
I ment not to cool it but renew it. Also the O2 sensor?
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