86rutmaker

hello everyone, im new to the jee world and new to the forum.
I recently bought an 86 cherokee 2.5l.. highly modified suspention-body. (im posting in the stock section because the engine is stock) i went mudding to test it out and it did great 2 or 3 days later i start getting a slight sputter and she dies, it wont start, untill my buddie pull starts me. and after that its been suttering worse and worse. yesterday i go to start it and it didnt fire, so i spray some either in there thinking that it might not be getting gas, i was wrong, no spark. i put a charger on it and after a little bit i cranked it, the engine turned over fast and finally fired with massive slugish throttle response. it fired fine after that but has been acting like it runs out of gas, or its missing.
i have searched but no one has had my exact problem. please help, thanks for your time

cruiser54

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, failed emission tests, and wasted money replacing components unnecessarily.
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.
For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.
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 03-04-2013

cruiser54

Since you went mudding:

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals making sure they haven’t retracted into the plastic holder, and then plugging it back together. There’s a critical 10-pin connector for the front lighting system located in front of the air cleaner and behind the left headlight assembly. Don’t miss that one
. Also be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.

ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then plug them back in. I do this on every Renix Jeep I purchase or work on for someone else.

Revised 07/23/2012

cruiser54

Also:
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 and some fine sandpaper.

Squeeze the springy contacts closer together with some needlenose pliers. 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.

I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.

　

Revised 04-04-2013

86rutmaker

thanks for all the help. what is the braided wire on the firewall for exactly

cruiser54

Major ground for alot of electrical components. Critical. Take care of it. Add to it. Don't ignore it.

DFlintstone

Not really your "symptom", but always good to check the MAP tube.



There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich. (black smoke, fouled black plugs). You can pull the line off the MAP and feel for vacuum with your finger. If it runs!



Besides your grounds, it can only take a minute to check that tricky CPS. (we're lucky here, it's a pain to check the newer ones)



AC voltage CPS test; Small clips on the meter leads really helps.

Unplug the connector at the back of the manifold with wires going down to the bell-housing/cps.
Probe the two wires to the cps with the meter set on AC volts. (a 200 scale on mine).
Crank the engine and note the voltage. (jump it if your battery is low)

Mine somehow works with only .3 my wiring/grounds must be pretty spiffy. .5 seems to be a good mark. One article talked of .5 to .8. **Update, it soon failed. I installed Napa #css980 in my 90.**

86rutmaker

i think i may have fixed the problem, i cleaned off the grounds like cruiser said and i drove it, it hasnt done it yet, thanks for everything guys have been a big help

86rutmaker

so it started doing it again, so i pulled of the same ground wires and wire brushed and put them back on, it started sputtered and died hasnt started back up, it does not have spark now, what could be the problem

cruiser54

Test your CPS.

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 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.



　

　

Revised 01-26-2013

86rutmaker

can relays slowly go bad? and cause my symptoms? cause two are junked my fuel pump relay and another that im not to sure what its for.

DFlintstone

Those SPDT, (single pole, double through), relays actually seem pretty hardy. They DO fail, but more likely if there is a problem it's where they plug in. There is a diagram in my signature that shows them. You can swap them around, like put #4, (AC) in #2 spot, (fuel, (and more)). I guess in our 87-90 Renix Jeeps, the fuel pump relay handles stuff the ASD (auto shut down), relay handles in the later OBD Jeeps. Something like that anyway.

You can use the $4 harbor freight meter (DVM), to check that CPS Btw.

86rutmaker

i have 3 relays, one is for fuel pump, it is out and one tothe left is out, but the one on the far right works, i dont have ac is that what its for?

DFlintstone

Oh...86. It is helpful if you fill in your info so we can easily see what you have. Scuse me...the 87-90 has the four I mentioned. I Usually pick up a few relays any time I'm at the JY. Anyway, maybe stick new, or replacement relays in any/all cleaned sockets, and take it from there.

I still think you should check the CPS. Since you were lucky enough to hear from Cruiser, I assume your 86 can be tested that easily.

86rutmaker

i got it to run havent been on in a while, no more sputter. replaced relays and cleaned the wiring to the tranny cps maybe, i dont know where that was located. thank you for all your help guys