90 Start/Stall/noStart (already searched)

[Djmack]

Ok, to start off with this, i did a little research on this topic, and yes i used the search function and found a little. But, im not satisfied.

My 1990 XJ Will randomly start with little issue. Run at idle fine, Rev up fine and really purr's. But when i go to put it in drive, and give it gas, my RPMs will run, then dip to 0 and rise again and dip about 2 more times before complete stall. After this, it basically fails to start again. I check for spark coming straight from the coil, and my friend claims that it went from nothing to something and back to nothing. So it could be ignition related. I have come up with a couple of different situations, all which cost either alot of time, or more money than i want to spend at this moment.

1. GROUNDS. I understand this is a big issue, unfortunately the ground locations are in completely different area's than my '95. So ill look those up and refresh them.

2. I replaced the coil, but not the ICU. The ICU could be bad, or have bad connections. I could clean the 2 terminals to start with and see where this gets me.

3. I Replaced the CPS. (btw, hardest part i've ever replaced on a jeep) After doing this, it started right up and i thought i had everything good and then the symptoms came back. I did read somewhere about a TSB stating that you need to set the cps properly all the way down. TSB

4. My Ballast resistor, Which no one seems to carry, is broken on the mount. when everything is operating properly, i hear the fuel pump prime and everything. So, this isnt very high on my suspicion list.

5. Its a Renix.

 

[magimerlin]

Just bypass the fuel pump ballast resister. Almost all of us do that. Both my 89's have their ballast resistrs bypassed. Have had them that way for years with no issues. The CPS connector can be a bad connection point. When it dies unplug the CPS then plug it back in. Do this a couple times and then try to start it. If it starts either hard wire the CPS or you can get a new connector and wire it in or you can try to clean the old one.

 

[cruiser54]

Check your CPS, even though it's new.

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

 

[cruiser54]

If you have a 90 with a 95 engine, the grounds should be in the same place.

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

 

[cruiser54]

This might help with the spark issue as well. Takes 5 minutes to do.

Renix Jeep ICU/Coil contact refreshing
　
　
The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.
The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.
Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.
While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　
Revised 11-29-2011

 

[Djmack]

If you have a 90 with a 95 engine, the grounds should be in the same place.

The engine in the 90 is original.. If and when i can get it running, i plan to clean out the entire engine bay from oil and do a full gasket rebuild. then i will sell it.. i cant stand the renix years. every time i look under the hood of the 90, it makes me appreciate my 95 more.

I remember reading this article some where.. ill be sure to try all the CPS stuff first. and as mentioned, the coil is new, so ill just have to clean the icu connectors and check the connector pins.