bullheimer

This sux. My new autozone cps showed .2 volts (AC), and so i gotta new factory one and it's showing me the same thing. How common is this?

kjc

Not sure what you're talking about.. what is 'cps' ? And if you're measuring voltage on a Jeep, you should be measuring DC, not AC

vashxj

what exactly is the problem and is sounds like the cps isnt bad then

cruiser54

CPS is Crank Position Sensor. It generates an AC signal to the ECU.

OP, you are measuring the signal right at the CPS connector, right?

This may help:

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 it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011

bullheimer

i tried drilling the holes on the autozone unit and got no change. i am sucking hind tit

F1Addict

Just curious, what is it on the flywheel that signals the Hall sensor in the CPS?

Is it possible that the CPS isn't picking up a good read from whatever it is on the flywheel that triggers it and that the fault lies with the trigger on the flywheel and not the CPS? Through much research, I've never read of that happening but just wondering if it's possible.

I guess it's a bit of a crap shoot with Auto Zone CPSs. I got mine there (Duralast SU3228) and it read .52v AC when I tested it as Cruiser54 suggested. I figured, for $28 I'll take my chances. So far it's worked flawlessly however, when I can afford it, I'm going to pick up an OEM CPS and swap it out, keeping the Duralast in my traveling box of spare parts... just in case. I've gotten the swap down to a science, without lifting the truck I can switch them out in five minutes.

bullheimer

that is about all i can think of too. the deal is this jeep ran until it was taken to a friend of a friend for a tune up and has never started again.

i am going to look underneath and try to see if there is some smegma on the flywheel as you say. maybe if i clean it up or something. but i don't hold much hope for that working. i will be trying some used ones from the junk yard they want $15 each for. however, i don't expect those to work either, it might have been them that put the jeep in the yard in the first place.

reading that post tho, cruisers post says its a build up of clutch material. i have an automatic. so not looking like that is going to be any kind of issue. i have looked for a neutral lockout switch on the bottom of the column, but it has a shifter in the console, so no lockout on the column. maybe on the trans?tx case? have to take a closer look. would the engine turn over at all tho if that were the case? i dont think so, and it is cranking. i will put my charger on it when i try to start it this time. i had the charger on it the first time i measured but i was measuring DC volts. the time i measured AC it wasn't cranking very strong.

cruiser54

There are multiple slots in the flexplate. If it's turning, the signal should be generated.

F1Addict

It doesn't have to be clutch material. I suspect the build-up on my CPS (also an auto, '89 I6) was caused by small shavings being released from the flex plate by the starter motor. When I removed my old CPS it was covered in iron fuzz. I cleaned it off and got it to start but as soon as I put it under load it died so my old CPS was bad. I replaced the CPS and it started and ran perfectly until I saw smoke coming from the engine bay and realized I hadn't secured the wire which was now melting itself to my exhaust manifold (don't do that!). I pulled the CPS to repair the melted parts and discovered that, once again, it had been covered in iron fuzz, but less this time.

If it cranks, it's not the Neutral Safety Switch, which would prevent current to the starter so it wouldn't even crank.

F1Addict

...and I'll stop calling it a flywheel :/ This is my first automatic... ever. Still coming to terms with the moving parts and their names.

Flexplate flexplate flexplate.

bullheimer

my IDEAL digital volt meter reads .1 when its not connected. even .2V

so, i also have a running 89 MJ (i'm working on a non running 89 cherokee, i shoulda mentioned) so i slapped my DVM on my running vehicle and guess what... same exact volt readings, so it means NOTHING what i just measured.

so i still have to, after that last post about flex plates, clean that off perhaps. but i am starting to think it might have nothing to do with the cps.

thanks for all the replies. this Website has gotten extremely popular. posts don't stay on the front page for long anymore. oh well, hope the quality of the answers improves with the volume. peace out homies. i'm off to see the wizard. (but if it starts after i clean/check the flexplate, i'll be sure to come back and tell y'all about it. )

F1Addict

I'm beginning to think your problem may not lie with the CPS. Have you checked for spark? Is your fuel pump priming normally? What led you to suspect the CPS?