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How often does CPS go out?

Chuckanut

NAXJA Forum User
Location
Moses Lake WA
While working on another problem I had, found that my Jeep doesnt want to start AGAIN. (1989 XJ) I'm on my 2nd CPS. Just put the latest one in a week and a half ago. At one point it did start then died about 20seconds after. Now wont start again.
 
Might be the connection. Unplug it and plug it in a few times and see if that helps. If it does you might want to hard wire it, i.e.- get rid of the plug. It's common to have to do that on the older models.
 
Test the "new" CPS using the following instructions. They can be junk right out of the box.

Renix CPS Testing and Adjusting
 
 
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

 
 
Revised 07-30-2012
 
While working on another problem I had, found that my Jeep doesnt want to start AGAIN. (1989 XJ) I'm on my 2nd CPS. Just put the latest one in a week and a half ago. At one point it did start then died about 20seconds after. Now wont start again.

I have never replaced the XJ's CPS. It's a 1990 with 235K on the clock. I've had it for 10 years.

Yeah, I know, right?

I replaced the CPS on my MJ 3 yrs. ago because it had been sitting in a barn for ~~5 yrs. when I got it. The PO said it wouldn't start. It would turn over, but not start. He delivered it to my house on a trailer. I put in a CPS and jumped it. Fired right up.

I used that same CPS that was on the BA/10. Swapped over to the AW4.
 
I have never replaced the XJ's CPS. It's a 1990 with 235K on the clock. I've had it for 10 years.

Yeah, I know, right?

I replaced the CPS on my MJ 3 yrs. ago because it had been sitting in a barn for ~~5 yrs. when I got it. The PO said it wouldn't start. It would turn over, but not start. He delivered it to my house on a trailer. I put in a CPS and jumped it. Fired right up.

I used that same CPS that was on the BA/10. Swapped over to the AW4.

You do realize that you just jinxed yourself, right?
 
I think some of the new Renix CPSs are bad right out of the box. Mine was, from AZ.

There is an angel hair sized coil wire from a coil around the magnet sealed in side that is mechanically fastened to the large gauge connector wire, that is not soldered, just bare metal on bare metal, sealed in the plastic, and if it is not a solid contact, it comes and goes, and even arcs inside the sealed sensor. My new one screwed with me for weeks before it finally failed completely with an open circuit while I had the test meter on it. I bought my last ones, Standard Brand from Rock Auto, made in Italy, not China, and they are working great. The new bad one (AZ-China) was a sometimes no start, but ran fine once it started.

You also need to follow the steeps to drill out the mounting holes one drill size larger, and move the CPS a little closer to the flex plate or fly wheel when you clamp it in place with the bolts, so you can get at least 0.50 AV volts at cranking RPM out of the CPS. There are several old threads on the MOD here with me and Cruiser54 debating it, and discussing it......
 
I think some of the new Renix CPSs are bad right out of the box. Mine was, from AZ.

There is an angel hair sized coil wire from a coil around the magnet sealed in side that is mechanically fastened to the large gauge connector wire, that is not soldered, just bare metal on bare metal, sealed in the plastic, and if it is not a solid contact, it comes and goes, and even arcs inside the sealed sensor. My new one screwed with me for weeks before it finally failed completely with an open circuit while I had the test meter on it. I bought my last ones, Standard Brand from Rock Auto, made in Italy, not China, and they are working great. The new bad one (AZ-China) was a sometimes no start, but ran fine once it started.

You also need to follow the steeps to drill out the mounting holes one drill size larger, and move the CPS a little closer to the flex plate or fly wheel when you clamp it in place with the bolts, so you can get at least 0.50 AV volts at cranking RPM out of the CPS. There are several old threads on the MOD here with me and Cruiser54 debating it, and discussing it......
I've never heard of drilling out the mounting holes. I'll look for it. Well time for me to go get a voltmeter. Thanks for the help everyone. Wish me luck
 
Okay. Well just went out. Jeep didn't start. Pulled apart CPS plug, inspected. Plugged it back in. Fired up. While it was running for a min or two, I messed with the wires/plug to see if I could get it to die, and it did. Tried starting again, no start, messed with plug/wires again, fired up. While running, again messed with JUST the Jeep side of plug and died. So this tells me the wires on the Jeep side if the plug are bad. Would you guys suggest hardwiring? On the up side, my heater works now. Which was the original problem I was working on :)
 
I would just replace the connector. They are dirt cheap on Ebay, Google "Ebay GM Weatherpack connector". NAPA may stock them.

I have replaced several of my connectors as the plastic cracked from age.
 
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