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Ground Refresh Cable Size


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Hello.

 

I will be doing this today but was wondering if anyone knows if a 6g cable would be ok for block-firewall and battery neg-rad grounds? I have a lot of power wire left from an amp I used to have but it is 6g vs the 4g recommended here.

 

Improving the Instrument Panel Ground

The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, you will see a black wire attached to a shiny piece of metal almost directly above the hood release knob. The screw will have either a ¼" or 5/16" head on it.

This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.

The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.

Make up a jumper wire with #10 gauge wire about 10" long. On one end, crimp on a ¼" round wire terminal. On the other end, crimp on a 3/8" round wire terminal.

Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point.

Look above the driver’s side plastic kick panel just forward of the top of the hood release knob. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.

**Special note for Comanche owners: Make your jumper wire 12" long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**

 

 

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 terminations 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 terminations. Inspect to see that none of the terminations 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 meta, clean and polish the cable termination, 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 termination. 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 16’ long with a 3/8" lug on each end works great and you can get one at any parts store already made up.

 

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.

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Probably be fine, but if you've got more cable left over and get put ends on it, do this.

 

Make another cable to run from the dipstick tube stud to the 8mm stud on the passenger side inner fender just below the upper shock mounting area.

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Probably be fine, but if you've got more cable left over and get put ends on it, do this.

 

Make another cable to run from the dipstick tube stud to the 8mm stud on the passenger side inner fender just below the upper shock mounting area.

 

 

 

I used 4g and soldered my lugs.

 

 

Me, too. But two 6 gauge cables will be fine, especially having one from the critical dipstick tube stud to the chassis. Actually, I have a 4 gauge from the stud.....

 

That is what I thought as the 6g is larger than the stock grounds. I planned on adding a jumper to the stud too but was unable to get it off as the stud is loose and I didn't have a female tamper-proof torx to hold the stud while getting the nut off. Also noticed the PO moved the neg terminal from the battery to mount to the stud so I will likely just clean the stud and mating grounds as I have a jumper from neg cable to the firewall anyways so once the stud is cleaned up I don't think there is a point adding a chassis ground to it as there is already one on the neg cable is there?

 

Original Dash Ground

 

New Ground Termination (other end of jumper cable)

 

Negative Cable to Chassis (Rad mount, and yes, I know I need to replace the terminal as it has been badly beaten for some reason)

 

New Block to Firewall

 

Had a lot of fun at the end too as I noticed my Serp belt was half cocked off the PS pump pulley and upon resetting it back onto the pulley in it's propper grooves I discovered the PO removed/lost the adjuster bolt for setting belt tension. A little cursing and rummaging through the spare hardware bin and I managed to find a nut/bolt combo that would grab enough to set tension and be able to drive home...

 

Joys of used vehicles I guess...

 

Thanks all

Dave

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Get that stud tight. It's super important!!!

Yup. Tomorrow I'll be heading to the parts store to get the proper socket and tackle breaking the nut off, retorquing the stud and cleaning all the contacts to finish my ground upgrade. Then the c101 and I can move onto mechanical checks/repairs.

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So I got the sockets the other day, but of course when removing the stud today the torx part snapped off in the first few seconds :mad:

But with some convincing I managed to get the stud off anyways and cleaned it all up. Also cleaned up the negative cable as it looks like the PO clamped some insulation in where the cable meets the terminal...

 

 

She seems to idle a bit nicer now, and I believe it has eliminated the cold stumble so I'm pretty happy for sure. Now just gotta figure out why my truck either runs cold or if it is just the temp sender being the wrong part for guages (my po installed the speedo cable designed for from the trans to the cruise control straight to the cluster so it would really not surprise me...)

 

Cheers

Dave

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