Ground Cable Getting Hot

[MJholic]

Have recently become a Comanche owner. Started two months ago. I'm up to 5 trucks with one more on the way as soon as I get one road worthy enough to go get it. My kid lost the keys to my Cherokee which has been my primary road tow vehicle with a tow dolly. Any way I have two trucks that have about one foot of insulation melted off of the ground cable back from the engine attach point. I'm puzzled by this because of the main ground cable from the battery going to the engine puts the biggest load from the starter directly in the proper current path. The insulation meting is coming from heat. It is either internal in the cable due to current load or it is external from the engine. Because I have 2 trucks with the exactly the same conditions I would expect that somebody else has seen this. The starter on one of the trucks that I can start does sound really loud when compared with my 1995 Cherokee. Is it just a bad starter overloading the cable? 

 

MJ Holic

 

 

[86FUBAR]

I just went through a grounding issue with my manch a few months ago after I burned the ground strap from the cylinder head to fire wall , my problems may or may not be the same as yours but this is what I came up with . Wile driving and after hitting a bump usually the lights , stereo and sometimes the engine would cut out . I figured it was a power issue so I started cleaning all the power and ground connections along with the bulk head and all other plugs . What I didnt see was the main battery cable to the starter had rubbed a 3/8" hole in it and after all other connections were clean and having moved that wire around a bit the whole thing went up in a ball of smoke when I hit the key . After that I fixed the cooked wire and added 4 more grounds to the engine at various points as it turned out I only had the one that burned up.

[jimoshel]

You should be able to visually inspect the area and see if there is something near by, exhaust pipe, exh manifold, cigar smoker, etc, that is melting the insulation. My guess would be dirty, corroded connection(s) in the circuit. Take a volt meter and go across each and every connection in the circuit. There should not be a greater than .1 volt drop across any connector. Take the reading while cranking the starter.

[MJholic]

Thanks. I did check the cable just now with an ohm meter and amazingly it has 0.1 ohm resistance from the crappy old battery clamp thru the exposed section of cable to the round lug that goes on the engine block. I was maybe thinking it could be the crimp on the ring lug but that just got ruled out. So that leaves the ring lug connection to the engine block which I can't check now that it's apart. I was going to attach a picture of it but not figuring out how I do that just yet.

[MJholic]

Put new cable and a used starter on last night. It cranks much better than before. Got a steering box leak to fix and a rough running engine to take care of and I will have my first functional MJ. It's a 2 wheel drive 1999 long box from Tennessee that is unbelievably clean underneath. I'm picking up my AX-15 ,231 this weekend. Got the rest of parts needed for the 4x4 conversion from my completely rusted in half donor 4x4 that is getting split up between at least 3 trucks. My first truck was a lifted 1986 from Florida. Real clean except for the wire harness fire that took the 2.5 out. Converting it to a 4.0 from the donor. I have figured out on my own and with reading on this site the things that will have to happen to it to get it switched. There does not seem to be a definitive list for this undertaking which I think needs to be available to other 1986 owners. Also a few bits of the threads I saw about the differences are wrong.  So If some one could help me figure out how to put pictures up I intend to show and list my conversion process that I'm mid stream into. I got side tracked getting a tow vehicle going because of my kid losing my keys to the Cherokee. I have searched the help section and there is nothing there about picture posting. Need help please. Also is there a place where all of the short hand parts conversion descriptions are defined. I'm a fast learner but what would be helpful is a definition of the part and from which year model jeep the part can be found. Also the vin number decoders are mostly  wrong. The one from Jeep all most worked for all 5 of my trucks. I have two 1989 trucks. One worked with the 1989 listing in the decoder. The other one worked when I used the 1990 listing. I saw another post talking about this. So they shifted the codes somewhere in the 1989 production year to the 1990 standard.

 

MJholic

[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

[MJholic]

Typo on my Tennessee truck its a 1989 of course.

[MJholic]

I have seen this page and read it a few times including all of the points. Questions is it is my understanding that the Renix trucks are 1986 1987. I'm sure some to most of these tips apply to the Bendix injection trucks. Am I right that the Bendix injection trucks started in 1988? Is there any thing that I need to NOT do on the Renix list if I have a Bendix system??

 

MJholic

[Strokermjcomanche]

Renix is 86-90

[MJholic]

List of what I got. Will have to check tonight on two of them

 

1986 -  Renix

1988-  ?

1989  -Bendix

1989 - ?

1990- Bendix

 

My 1989 does not agree with Your 86-90 list of Renix. The 1989 is my donor which is completely stripped and I'm 100% sure I pulled a Bendix Main Module out of it. I have to crawl under the dash's tonight to check the other two. 

[64 Cheyenne]

88& 89 both Renix.  No Bendix by itself, Renault + Bendix = Renix

86 is its own animal by its self.

[HOrnbrod]

As the man said, Renix = 1986-1990.
 

The Renix control system prior to 1991 can be tested only with Chrysler's DRB tester, and the diagnostic test modes for 1989 and later engines with SBEC controllers differ from those provided for 1988 and earlier.^[10]

Model years:

• 1986 - Renix TBI available on Jeep 2.5 L four-cylinder engines.
• 1987 - the new Renix controlled 4.0 L six-cylinder engine was rated at 173 hp (129 kW; 175 PS) and 220 lb·ft (298 N·m) of torque.
• 1988 - 4.0 L output increased to 177 hp (132 kW; 179 PS) and 224 lb·ft (304 N·m) of torque, due to higher compression ratio.
• 1989 - Changed to Renix MPFI.
• 1991 - Chrysler Corporation (then the owners of the Jeep brand replaced the Renix control system with OBD-I-compliant control electronics, the Chrysler HO EFI).

The Renix control system was only found on the 1987-1990 Jeep Cherokee and Comanche with AMC-designed engines (the control setup used with the 2.8 L (171 cu in) V6 was OBD-I General Motors, and the early Diesel was a 2.1 L (128 cu in) Renault turbodiesel I4 that used its own specific control setup.)

 

[MJholic]

Roger that. So to restate it a Renix system will have a Bendix control module except for the 1986 which has a Renix control module. Did I get it right? Appreciate the education.

[cruiser54]

Roger that. So to restate it a Renix system will have a Bendix control module except for the 1986 which has a Renix control module. Did I get it right? Appreciate the education.

Bendix and Renix are one and the same.

Renix was a joint venture of RENault and bendIX 

 

That said, the ground refreshing and upgrades apply to your rig. 

[MJholic]

Thanks again!  I can tell that your list is going to be a good thing to go thru. I noticed a big difference in engine performance by just redoing the grounds by the dip stick. I have a leaking exhaust manifold between the manifold and the head on the front cylinder to fix which will eliminate loose manifold bolts and I need to make sure that the CAT is not blocked. I have a rough idle with a hesitation just off idle and a back fire when I let off the gas. Also engine does not warm up very fast so I probably need a thermostat also. Need to get all of that fixed and then hone in on your list. Got rid of the death wobble this weekend. The cross bar going from frame to front suspension was loose at the frame connection mount. Had a elongated tapper hole in the bracket. Grabbed  a used one from my donner truck. Got it out on the Freeway and found out my rear end is going out. Front bearing on carrier is getting hot. I was hopping to use the truck in 2 wheel drive mode for awhile before I converted it. Guess I need to upgrade sooner. I want to put disk brakes on the Dana 44. Will the jeep liberty brakes fit the 44? Do you just get the mounting brackets and buy new disks and calipers? I've seen the bigger power assist for the master cylinder which I intend to do also. 

 

MJholic