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 itself as shown in Figure 2 as Connector A, 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 to 3/8″ from the stock 5/16″, 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.
Another little tip to save tons of aggravation is to stick a bit of electrical tape to your 11mm socket and then shove the bolt in after it. This reduces the chances of dropping that special bolt into the bell housing. 
Revised 8/8/2016
Hey Guy, thanx for your tips!
Question: Do you think running a ground wire from the upper mounting hole to the engine or body would improve the signal from this sensor?
maybe put it in line with the stator/distributor ground to improve the overall sync? All this assuming that those little wings on the CPS are designed to ground..
It doesn’t need a ground. It sends a signal to the ECU.
10-4
No.
No. That sensor generates an AC voltage signal on it’s own. Tip 7 will help with generating a stronger signal.
Which Tips have you completed by the way?
No. I have seen problems when the right bolts are not used.
My cps voltage fluctuates between 3.85 and 4.10 even in a no start situation. Change or not change?
Meant to say the readings are the same for start/ no start situation.
Will my cheapo Harbor Freight meter be able to do this ac volts test? The AC VOLTS section of the dial only shows 750 and 200 positions.
Yes, that’s a safety setting internal to the meter. 750VAC will lose the resolution that 200VAC offers. It will work, but a cheap unit might not be very accurate. Is it an analog or digital meter?
Its digital. Cen-Tech #90899 So put it on 200 ACV position and try that? Ok thanks alot, I will let you know how it works.
Cruiser, thanks for all the help.
I measured my CPS and was only getting .3 AC So I replaced it from autozone and got .2, I bought a new one from NAPA and I am still only getting .2 . What should I do next? fuses? I’ve checked battery, alt, starter.
– new plugs, cables, ignition coil, oil pressure sender, map sensor.
-just did all that rebuild work that we talked about in the other post and now getting crank but no start condition. 89 XJ Laredo 4.0 auto.
-only thing is transmission has a small leak..
Thanks
Still need help with this please. If I’m getting spark does that mean its not the CPS?
Thanks
Yes.
Yes, if its getting spark the CPS is good.
Check fuel pressure and IAC motor, AIT, CTS and O2 sensor
OK, so I am picking up 1.2 amps from the CPS. My Comanche is currently in a no spark condition. Is it possible for there to be too much voltage from the CPS? Also any other suggestions on troubleshooting the no spark condition? I am working my way through the tips !
Thanks!
You should be measuring AC voltage while cranking. I’ve seen 1 AC volt with no issues.
If you have an 87 or 88, keep in mind the signal must travel through the C101 connector and that can reduce it significantly before it gets to teh ECU. Tip 2 and 27…….
The CPS puts out as much as 5-6 volts at idle-2000 rpm, when running, so higher cranking voltages are good.
I just visited your website!!!
Yeah, come on out and visit !
So I am still in the crank all day, no start condition. I have recently eliminated the C101 connector, cleaned up the ignition module and replaced the coil. I guess next is the ECU harness, and then maybe I start tracing back from the Spark plug wires for spark?
Any other suggestions would be appreciated.
Let’s make sure you’re testing the CPS correctly. Tip 7 gives detailed instructions. Any questions, let me know.
Where would you look next if still no spark after confirming voltage exists from the cps?
Thanks!
Greg
Coil, coil wire, distributor cap, rotor.
OK, I will try testing it again. It seemed pretty strait forward to me, is there something people commonly miss when testing??
Thanks
OK, will do. I recently tried replacing the coil, my distributor cap and rotor are fairly new. I did bend up the button and shined everything up with some sandpaper and still nothing. I plan to hook up a spark tester to the coil next to see if I am getting anything from it.
I’m not sure how related this could be, I recently replaced my fuel pump, new fuel pump relay, etc. I am no longer hearing the signature groan when the key is in the on position. I have bypassed the ballast resister, refreshed tail light ground and added a ground as you recommend. I DO hear a slight sound from the pump at the very end of cranking, but that’s it. I plan to borrow a fuel pressure gauge, I guess I will be looking for pressure during cranking as well as just key in the on position. So two questions … Should the pump be active just with the key on?
I am wondering if somehow my lack of spark could be related to some issue with my fuel pump/pressure?
Also, FYI, so far I have completed tips 1-5, 7, 9, 27 and 29….
Glad to see you’ve done all those Tips.
Definitely check the fuel pressure. No spark will not cause no fuel pressure.
I have personally seen numerous fuel pump replacement failures if Bosch pumps were not used.
OK, thanks. The brand of the new pump is air-tex. I was looking for a bosch, but also needed the sending unit. I guess if I have to crack back into that bad boy I will just swap the pump itself out for a bosch…
Alright, here’s an update we are back up and running!!
So, after replacing the fuel pump I was getting no spark and no fuel pump groan. I jumped the relay plug with the key on to find that the pump did in fact work. So the fact that the relay was not receiving a signal for the fuel pump, as well as the ICM not receiving signal for spark lead me to ordering an ECU from JC Whitney. Plugged it in and fired right up!
Thanks again for your advice and of course the tips!
Also, for the record, I went with a 1990 ECU in my 88 comanche. I am feeling some extra get up and go for sure, but then again I did eliminate the C101 so who knows maybe both are to thank!
I have a 1990 Comanche. The cps is located in the cutout on the firewall and is hard to get to. I got some different tools (shorter) and it looks as if I’ll be able to get to ths cps now. I hope.
My 87 XJ was knocking real bad. Flex plate replaced along with crank sensor while it was apart. Ran great before, now it will idle but not rev up. Loud rapid backfiring from exhaust and no power in mid to upper rpm, due to running awful. Ordered 2 flex plates from one store and they were different than what came out of it. I ordered 3 more from another store to see if manufactured wrong, they all had the holes stamped too far away from the ring gear. Ordered another one from another mfg. after talking with technician, and measuring the distance from the ring gear to the openings in flex plate. This one matched. Needless to say we compared the old one to this one closely. The mechanic put the new flexplate in and said it runs good…wrong. Still sounds like a machine gun when you accelerate enough to make it downshift. I read all the comments about bad sensors so I get a NAPA sensor, same problem. Remember, this Jeep ran great until I had the flexplate fixed. We tested voltage and were all over the place with .1 to .35 and sometimes to .6 We drilled out the holes to 3/8″ and got .3 to .6. Took it out and removed 1/16″ off the bottom of the sensor bar, now we are getting a steady 2.0 volts. One sensor would allow motor to idle but it would not rev up at all. So I now have the sensor that reads 2.0 volts in it. WHAT HAPPENED? Still backfires like a machine gun.
I have heard of faulty new flexplates for Renix models.
Maybe try a used one?
Mr. Cruiser54,
Thank you for maintaining this website!
I have this same problem with a cracked flexplate replacement. My 1988 Jeep Cherokee Laredo 4.0L ran great since 2003 until I took it upon myself to replace the cracked flexplate. The flexplate had cracked recently due to a transmission bolt backing out. A previous owner had replaced the engine and the E12 bolts were not even in it. Please note that other than the engine replacement many years ago, there have been no other modifications made to this Jeep.
Anyway, in my backyard, I replaced the flexplate with an Omixada flexplate. That flexplate was defective because the 120 degree shutters were out of place by about 2 inches. I didn’t realize the importance of that fact at the time. As a result, the engine would start and idle fine enough, but once the accelerator was pressed, there was lots of backfiring but the engine rpms were robust.
The second flexplate from ATP Z-205 was analyzed more closely, and it seemed to be a winner. Also, according to many posts, I found that the flexplate should only bolt onto the crankshaft one way. However, this one starts after coaxing with the accelerator and will idle at about 200 rpm. Very disappointing. After testing the fuel pressure which is good, I tested each cylinder’s spark with a spark tester. This is what I found:
Cylinder 1 = No spark
Cylinder 2 = Good Spark
Cylinder 3 = Medium Spark
Cylinder 4 = Medium Spark
Cylinder 5 = Good Spark
Cylinder 6 = No Spark
I laid a spark plug on the block coming straight from the ignition coil. It sparks consistently and good spark.
Since it will only fire well on two cylinders, it barely moves under its own power.
At this point, in your opinion, do you think I need to get a used flex plate, or do you feel that there is some type of new electrical problem that I need to investigate. After the second flexplate, I bought and installed a new CPS and modified it like your page says to get it closer to the flexplate. No change. Like I mentioned, it does run but very poorly.
Your advice is much appreciated. I started this process a year ago, and with the number of hours I had devoted to replacing the flexplate twice, I had to put the problem away for awhile to remain sane. This was my daily driver until the flexplate replacement, and hunting season is coming soon.
Thank you!
Holy Moly!!
Test the cPS output.
Have you done the ICM/coil refreshing or have a spare one around?
I have tried to test the CPS but my meter doesn’t read that low of ac volts. I can try the ICM/coil refreshing too. Thanks for the reply. Holy Moly is right!
Back to follow up on my flex plate dilemma! After my last post, I ordered and received a very good looking used original 1988 Cherokee 4.0L flex plate from the rockitopauto eBay store out of Glen Flora, Wisconsin.
It turns out the ATP flex plate was made pretty sloppy. The 120 degree openings were in the right place. However, most importantly, the ATP’s measurement from the outer ring gear teeth to the inner ring that the CPS reads was 1/16” more than each of the originals. That is, the originals measured 7/16” from the outer ring gear teeth, and the ATP measured 1/2”.
Therefore, even with modifying the CPS to get closer to the flex plate inner ring, the ATP ‘s inner ring was still too far to get a reliable signal to the ECU. Thankfully, the original from eBay fired right up! I was truly relieved.
After putting everything back together and replacing all of the spark plugs for good measure, the Cherokee sounds just like it did before I started all of this a year ago. I hope this follow up helps someone. I have read many threads online dealing with flex plate replacements that didn’t get resolved. In retrospect, the Omix ADA plate might have been o.k. if the 120 degree openings had been in the right places.
Also, yes, the flex plate bolts onto the crankshaft only one way. And, yes, you can replace the flex plate in your back yard without pulling the transmission all of the way off. Use the two 12”-14” pieces of 7/16” threaded rod with nuts to replace the transmission to engine bolts method and a floor jack under the crossmember. It can be done because I did it three times by myself with this exercise! It ain’t fun, but it is possible.
Thank you Cruiser 54 for all of the tips that I will be working through shortly!
John, thanks for the update. You made my day.
Cruiser, I just finished going through 3 CPS units from NAPA. My old one was bad( quit on me while driving in traffic) . Two standard units,one premium. one standard gave .1vac, the other gave .2vac, the premium wavered from .2 to .3 vac and once gave .4vac. None would start the engine, the premium started once but the engine didn’t rub well at all. The guys at NAPA said none of that had ever happened before and it sounded like there was maybe another problem. Have you got any ideas as to what the problem might be? This is a 1990 Jeep Comanche Eliminator. I would appreciate help asap sir.
Sorry for the late reply. The website is supposed to notify me as soon as a comment is made. didn’t do it til today.
I just went through the same thing with a pile of new CPSs that came with a Comanche I bought.
Have you done the drill mod to move it closer to the flywheel?
I don’t know if my last post got thru so here goes again. I have tried from NAPA two CPS units, got .2 and .1 VAC, then a premium CPS and got .2-.3, one time .4. The store guy said it sound like I have another problem. With the CPS unplugged, what else could it be? This is a no start situation. Help!
Have you ever tested at the ECU to see if it’s getting the signal?
Check at C1 and D1 terminals.
Also look around your CPS connector and see if there is one just like it nearby.
There was a factory fix to put another CPS patch harness in and I have seen where the mechanic didn’t cut out the old one. Then, someone down the road accidentally plugs his cPS into the dead connector.
Looking to see how many more comments there are.
As explained earlier, I got NO notifications of anyone’s posts/comments here until today. Sorry.
Cruiser, if the cps is disconnected, is there anything else that could affect the voltage reading. I have gone through 3 sensors from NAPA and none recorded more than .3 vac. The guys at NAPA said they had never seen one bad out of the box like that and it seemed that there was another problem. What else could it be?
A dirty C101 connector if it is an 87 or 88.
Just curious – if he is getting low voltage when the CPS is unplugged, what would the C101 have to do with that?
Because low voltage at the CPS must then try to get through the C101. With a clean path to the ECU, a low voltage from the CPS might still work. That’s why the factory came up with a kit for the CPS wires to go directly from the plug to the ECU.
I put the premium CPS from NAPA in my Comanche, it has the holes drilled out. It still shows .1 vac. that’s the third one. Seems to me there is no quality control anymore. All they need is a test stand at the factory to test each one as it comes off the line. This is really crazy, you could go through a lot of money and time getting one that works.
I have a horror story on CPSs. Tried 5 on a Comanche I bought and none would put out any voltage. I had to modify the crap out of one to get a signal.
I modified the CPS as your tip and someone else’s tip said and it still wouldn’t start. Then I looked at the coil, all contacts were corroded and dirty. cleaned them all, used Oxgard on them and it fired right up several times in a row!
Woohoo!!! Glad to hear it.
Cruiser54 are both of the wires that connect to my cps supposed to have voltage? I have a 89 jeep Cherokee 4.0 and have gone through 3 cps and when I check them they have .1 volts and the two wires that connect to the cps have voltage in both of them going insane trying to figure this out please help anybody thanks
Hey Frank. What scale are you using on your meter when testing?
Should be AC voltage while cranking.
Thanks cruiser I was using the wrong voltage turns out it was the remanufactured ecu from cardone put the original back in and all is fine turns out the ecu was causing a lot of other issues going to buy a new ecu want to have a spare one cause there getting hard to find new and thanks for the awesome site it’s a renix owners dream and to all renix owners out there invest in a snap on mt2500 it’s a lifesaver thanks again
Glad to hear it. You can find ECUs in the junkyard.
https://www.youtube.com/watch?v=52CGI5GLiYk&feature=youtu.be
As for an MT2500, here’s an affordable alternative.
http://cruiser54.com/?p=568
That’s awesome I was reading about that probably on your site that’s now on the top of my list once again thanks
You bet.
Would the CPS be responsible for a start to stall or an intermittent stall? I’ve had 3 different cps sensors in there now with no reading at all, even with modifying them. One of them did show .5 volts for about a week but still had intermittent stall and start/stall issues before it went back to 0.
You have to wonder about the quality of these replacement parts.
So, it quit running when it began reading 0?
Hello cruiser, matt rowe from jeep forum. you said in a post that you modified your cps sensor to put out .8 ac volts. Could you enlighten me on the mod. Also, mine which is a 90, is the round style, my sons a 96 xj, has the square one.
Now with that said, do the cps after 92 are better than the early versions, if so, are the wires the same, so i could file the bell housing and make a later one fit, or is the housing able to fit a newer style in it, if the wires are identical, the plug that is.
I have done about 4 of your tips, and have to do the tb clean, injector upgrade(bought them already), I am going to do the iac motor. Have done all ground refresh except fuel pump.
They work differently Matt. Renix is one style, the later ones a different style.
How much is your current one putting out? Have you done my CPS bolt hole mod?
I have not done the bolt hole mod. I just put in a new one from Auitozone, a Durolast. I will check the voltage tomorrow and post back. It is running and starting fine now. But my son drove it to work for a coup[le months, then one day, no start. I picked him up from work, then we went back next morning and it fired right up.
Si bought this one in there now. I am going to buy one from napa, and make a tool and keep as spare. Probable weld a long extension, to a wobly socket, so i can change out the sensor with ease.
I’m having what l believe is a CPS issue but, l am a little confused. When testing the CPS l am getting 0.00 volts (yes in A/C mode) but the engine will start, but it will not rev beyond an idle. I do have resistance through the CPS. So, l guess the question is As long as the CPS is in place and a part of it’s own circuit, is it just starting and running on base timing?
It could be a weak CPS. Timing is controlled by the ECU.
Will do the bolt hole mod next, just had a no start condition. After using my klein meter, i had no voltage, but when moving the probes around the wires, the voltage came back to around .45 to .48. It starts now, but will buy another one, try it, and then buy a spare also. Thanks for all your tips and website. I will be doing more of your tips, have done about 4-5 so far. I have a 90. Pioneer./
You’re doing a great job. stick with it.
Hey thanks for all the wonderful information you are sharing with us! 88 xj 4.0 went ahead and ran a test on original cpsbefore swapping. Also ran a test after replacing with a new one from oriellys. my ac reading came out the same. 3.5. Any thoughts?
Are you having CPS issues?
I was thinking about cutting the plug out, and using water proof spade connectors. When i was looking at the contact pins in the plug from the cps, one was silver, and the other looked tarnished. Bit i have gone through no water, and we have had no rain. A spade as you know scrapes when you remove and reinstall. The cps i am working with is only 6 months old, a durolast.
You can tweak the original connectors to have better contact using a small pick.
ok, i can try that. Could i use electric cleaner in a spray can to clean it, but it might not remove tarnish though
My engine would run fine for the first 2 minutes of driving then it would start missing and backfiring badly. Discovered the CPS wiring was touching and shorting out on the exhaust manifold. Installed a new CPS from Napa and only getting .2 – .3 volts out of it. Kind of hesitant to modify it to see if I can get more voltage just in case I have to return it.
The wire routing is very important. So, it’s installed and putting out .2 to .3 AC milivolts?
Starts and runs? If so, you could just leave it and hope for the best or modify it. What happened to the old CPS?
You could repair the wiring with solder and shrink tubing and use it…..
It ran with the old CPS but was giving me trouble I believe when it was shorting out. I have the original one before rebuild, and the new one the mechanic drilled and installed. Both read . 2 volts. New one I installed without drilling to 3/8″ is reading . 3 while cranking. I have not hooked it up yet because there is no plug on my wiring harness I will have to remove the plug and solder it in. When I do I will add another length of wire off of the old CPS because the new ones are only about 12 in Long. Would you recommend drilling to 3/8 and see what that gives me. On a tight budget and would hate to waste $40
Going to drill it to see what that gives me.
Hard to say. If it runs with an old drilled one, go for it.
Running it with the distributor indexed timing light is showing firing at about 8 degrees from zero. If drilling this one gets me the desired voltage output would you also recommend advancing it?
If you’re up to it, go for it.
Thank you for your responses. Drilling it brought it up to .5 volts. I will take it back off and modify it.
Excellent!!!
Hi Cruiser. I put a Renix 4.0 in my 84 CJ7 in 2005, recently decided not to start I believe CPS is problem. It has a speed sensor on the front of the engine, under water pump, reading notches on small wheel. It doesn’t have a rear (bell housing) CPS. This might be a version of this engine that is less known, not sure. Have you heard of this setup?
It’s aftermarket. It was designed for applications such as yours. I would think it’s output could be tested according to my Tip on testing a factory one. It has to put out .5AC volts.
Thanks cruiser I will test the output. Ordered new replacement from Hesco which is different design all plastic. This one is metal with pivot to adjust position it must be really old. I suspect it’s going bad as after 10-15 from cold start the engine just dies when warms up. I’ll test this sensor and try replacement, if not this maybe fuel pump is on it’s last leg.
Why not test it and adjust it if possible?
Ok, so I purchased an 89 XJ for my son. The previous owner was clear that it ran very bad. Brought it home and I’ve been trying to figure out the problem since. The previous owner replaced the clutch, fuel pump, CPS, distributor, cap, rotor, plugs, and wires. After some diagnosis done by myself, I found no spark on cylinders 3 and 4. Great spark on 1 and 6 and mediocre spark on 2 and 5. I’m trying to provide you with as much info as possible but I’m sure I’m forgetting something. Any ideas as to what to look for next? Also, I noticed the Tach has a very random and inaccurate reading. (after I get it idling and rev the engine to what sounds like 4000 RPM, the gauge reads merely 2000 and it jumps around)
Have you indexed the distributor? This is gonna be somewhat a process of elimination.
H Cruiser, hoping you can advise on this. I got the front harmonic balancer mounted CPS replaced and seeing .5 AC volts. Also followed your instructions on grounding, cleaned the huge connector, tested fuel pressure at the rail. the 4.0 cranks and sputters/coughs but won’t start. I checked spark from coil to distributor and at plugs, Distributor/rotor are really new and still look good. Any ideas why it would sputter and cough during crank but not start? Thanks! Dan
Is the distributor indexed properly?
Tip 13.
Any point in testing the CPS if the jeep has no problem starting? I have been considering doing CPS timing advance mod also, but am trying to be wary of “if it aint broke don’t fix it”, also I don’t wanna break the plastic and have to buy the crappy new ones like was mentioned in that thread, is the risk worth the reward if It runs good anyway?
You can test it for fun. I agree with you on not doing the mod to a real old CPS. It could break. CPS advance isn’t a huge deal, but you can feel it.
haha I think I will stop myself short of testing sensors for fun, otherwise I may need a psych evaluation! I will leave it alone, thanks!
So my 88 comanche is having an issue with what I’m assuming is a misfire at this point just replaylced fuel pump and filter I have not done a pressure test but what I’m getting is itll run fine at lower speeds hit 3rd and it starts jerking real bad and losing power and its intermittent (one day it does it next day it doesnt) should I start with the cps are go elsewhere first like coil contacts etc ?
Of my Tips, which have you completed?
Test the fuel pressure as there are many JUNK new pumps sold these days.
I actually got this figured out the balance resistor dropped my voltage to low reading 8.9v output and fuel pressure was right at idle low when above
Hey there. I’ve got a good one for you.
I have a 90 Cherokee. 4.0. Was an ax15. I did an aw4 swap from a 98 Cherokee. I’m using a rad shifter to bypass any tcu stuff.
Sense the swap my Jeep has a bad stutter above 2500 rpm. I am using a Renix era flex plate and I have tried a different crank sensor. I’ve made sure my timing is correct
I’m not sure what to try, I’ve tried 2 new flex plates from the parts store with no change.
Before the swap it ran great. Now not so much.
I
Some of those aftermarket flexplates are made wrong. Can you find a good used one?
Do you dill the CPS sensor mount hole or the transmission mount hole?
CPS mounting hole. A photo should be in the instructions for ya. Enjoy!!
3 Seperate sensors from Napa all gave me .3 v so I’m gonna try drilling to get .5. Thanks for all the info, would have been lost without it. Might be back if it doesn’t work.
Thanks for the CPS tip, my echlin was at .3 out of box. Now .5 with new mounting hole diameter. It still won’t start but it ticks another box.
That’s good. You’re getting a signal!!!
Is it getting to the ECU though?
You have an eCU diagram I imagine? If not, contact me at cruiser54private@gmail.com and I’ll send you one.
Hi. I’m hoping you can help me. I have put a 89 Renix 4.0 into my CJ7. completed the wiring and it was running. The CPS signal was low .26. I hard started and ran like crap but was running. I was nursing it home from the muffler shop to trouble shoot/tune it and it died. No voltage at all from the CPS. Bought and installed two new ones and still not voltage. Checked the sensor ring on the flywheel was tuning by turning the motor by hand and all good. But still absolutely no voltage at all from the sensor when cranking. Any ideas? Any help would be appreciated. It’s been three long years and I really want to drive this thing.
Thanks in advance
Is it possible to test a new cps sensor without it being installed into the vehicle. Say hooking it up to the volt meter and then waving a screw driver across the magnetic pick up? Would that be able to tell you if the sensor is good? Or would it need to be moving much faster to generate ac current?
Not fast enough.
Thanks for the info, I had figured that was the case but I wanted to be sure before I went chasing my tail testing sensors thinking they were bad. Guess I’ll just keep swapping them into the jeep until I get one that reads some kind of voltage. I have swapped 3 Napa sensors so far and still cant even get it to register .1 volt on my meter. It is a digital Napa volt meter part number 700-2601. This should be sufficient enough to read that level of A/C voltage right?
I can’t speak for your meter’s calibrations. Look in the manual and see the ranges it works in.
Since by now you’re an ace at installing CPSs, take the one that gave you the highest reading and do the CPS mod and see what happens.
Do you know which color wires coming out of the vehicle harness go to which wires on the CPS harness? Does it make a difference? The CPS is labeled A (red wire) B (white wire) and C (no wire). The vehicle harness wires are purple/white tracer and white/black tracer. The previous owner cut the harness out. So I guess my question is, which wires from the CPS go to which wires in the vehicle harness and does it matter if they reversed? Thanks,
It does matter. The harness should have violet with tracer and a white with tracer.
CPS same thing.
Hi Cruiser54,
Thank you for the Great tips and your dedication to keeping all of us running!
I have an 87 xj which just started almost stalling / occasionally dying at idle. It seems to go away once it’s at full operating temperature.
I changed the IAC and had the same results. When I test the CPS it shows .1 volt, but it never has any problem starting. Should I still pursue the CPS, or be looking elsewhere for the stall/near stall during idle (until it’s warmed up)?
Note – several years ago I eliminated the C101 per recommendation 🙂 Thank you!
Mike
Review Step 5.
Changing transmission in 89 cherokee from BA-10 to a X5 out of 95 . Wondering which flywheel and CPS to use on the new trans.
CPS and flywheel from the 89.
So I swapped a 93 ax15 into my 87 comanche and I used the 93 flywheel. Now when I go to test the cps after replacing it with one from napa it consistently only read 0.1. Both vehicles were running before the swap.
You must use a flywheel from a Renix.
Damn alright thanks for confirming that for me.
I don’t know if my last comment went through so I’m going to try again.
I have a 1987 jeep comanche that I swapped a 1993 ax15 into, during the swap I used the 93’s flywheel. After installation the truck no longer runs, the old cps was reading .1-.2 so I bought a new NAPA cps it only read. 1 so I did the drill mod and I still only get .1 . Could it be the flywheel that is causing me grief.
If us use the renix computer have to stick with the renix flywheel I found out the hard way too
Yeah I guess its just one last kick in the balls before this thing is finished.
I have 88 cherokee crank no start has correct fuel pressure good spark and will only run idle / throttle up while ignition is held in start position I have tried ecu icm ignition switch and repaired some rough ground wire with no luck on a positive result I know the solution is simple but I am lost please any guidance will be appreciated.
Likely a bad ignition switch.
Cruiser, I’m “re-restoring” an old 88 comanche that hasn’t run in over 10 years. When it was parked it around 2011, I had restored it to daily driving status. I don’t remember if I started having cps issues or why I quit driving it other than kids. So today, I have replaced fuel tank and pump (bosch). I have a new NTK cps. (Also have an old autozone one (Siemens brand) and the original remix one. I get zero volts on the Siemens and ntk. I haven’t tried the original. So not sure what I am doing wrong. I’m reading AC 200V setting on the meter. I can jump the fuel pump relay and get it to run. So I know I have other wiring issues. I have cleaned most of the grounds that I know about. I thought my first step would be cps….but apparently, I need more direction.
Thanks,
Have you cleaned the C101 yet?
Cruiser, my 88 comanche 4.0 has been parked for years. I’m trying to revive it. I have 3 cps. One from autozone 10 years ago. A new ntk one from Amazon. A new napa one. All 3 gave me a .1 reading. I drilled out the AZ one and now it gets .2. I am still well below the needed .5. Worried that if I drill out the new ones that I will get the same results and then I can’t return it.
Thoughts??
Try drilling out both holes.
I’m having a no start problem on my 88 Cherokee. I have fuel pressure and spark. The spark seems maybe a little weak. I have eliminated the C101, cleaned the dipstick grounds, cleaned the ignition coil contacts, and connections. Tested the sensor grounds. Plugs and wires are 2 years old at most. I have replaced the CPS with a new Napa one and still haven’t gotten a reading over 0.1 ohms when cranking. Before it died on me, I had intermittent low idle, which occasionally resulted in stalling when stopped in drive. Also the Jeep would occasionally have a racing idle upon startup that would normally settle down when I tapped the gas. I’ve adjusted the TPS and cleaned out the IAC and throttle body. When running, the Jeep would normally crank for 3-4 seconds before starting. The battery tested good. I pulled the injectors and they are all working well.
I’d like to quickly point out that voltage readings may be different depending on the multimeter used to measure the CPS. Inexpensive multimeters will give incorrect voltage readings of the irregular and non sinusoidal waveform, and even a true-RMS multimeter may not have sufficient frequency response to measure the waveform.