Kuro89

I was driving to work and the the engine just cuts off, like I turned the key off no funny noises. It cranks but it won't start, first thing I checked was the cps and it checked out good, tested ohms and ac volts. Battery does while cranking it so I need to charge it so in the meantime I need a sort of checklist of the other possibilities that can cause a no start.
Note: I do hear the fuel pump prime so I think it is still good

F1Addict

Do you know when the CPS was last replaced? The past couple months I've read a number of threads where folks were facing the same crank-but-no-start situation and even though their CPS tested good (~.5v AC and proper resistance), replacing it solved their problem.

Other things to consider would be fuel pressure (clogged filter, bad fuel pump). I know you said you hear your fuel pump prime but that's not a guarantee of sufficient pressure to run the engine.

Start simple, check fuel pressure and pull a plug to test for spark. You need two things for combustion... gas and fire.

F1Addict

I think there are also some fuses/relays that could cause it to just die but I don't remember which one it is. Maybe Cruiser or Flintstone will chime in, they know a lot more than I do.

Kuro89

I think mine tested at around .6-.7 V, since someone made it "adjustable"
I did replace it and that one tested at .2v. I'll be refreshing the grounds and once I have a charged battery I am going over fuel and spark again

Kuro89

So besides the cps, I haven't ruled it put though, what else should I be looking at?

RTorrez1

Start by checking your fuel pressure with a mechanical pressure gauge on the fuel rail. Also make sure that you have a good strong blue spark. Those are the things that you need to start out with.

Kuro89

Once I have a good battery that is the first thing I am going to do after work
I also have to get it back to my house

cruiser54

This first:

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

This is never a bad idea:
Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

nickxj94

First thing you always check on a no start is fire from the coil then fuel. I bet the coil went out it happened on my buddy's 90 renix on the trail a few months ago the coil was very hot when it died and was not firing ran back to town got a new one its been going good ever since with no problems,

Slick761

Cps

cruiser54

Cleaning the ICU/coil contacts is a good way to prevent the coil from getting hot and failing. Good maintenance and takes 5 minutes.

Kuro89

The jeep is running thanks to all.It was the coil contacts on the ICU, they where a little dirty but most of all they were not tight around the posts on the coil. The CPS had nothing to do with this I tested it multiple time and if Rod Blagojevich was selling it he would say its F*****g golden. I have also gone through most of the ground refreshing and am going to ditch the braided cable soon.
I really didn't want to start a thread on it but I was getting desperate since it was on a random street.

cruiser54

Glad to hear it. Get your ground refreshing done and Rod will be proud of you.

And BTW, if you own a Renix 4.0, you need to do the ICU to coil contact refreshing to prevent this problem from rearing it's ugly head. 5 minute maintenance procedure.

nickxj94

Glad we help ya get it going

Kuro89

Yes, lots of work to be done. I was considering an after market coil and soldering to the ICU any thoughts?