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Ground wire confusion

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I was planning to do the "Big 7" battery cable upgrade and was looking for the ground locations on all the wires on my jeep. I'm not familiar with where the factory grounds should be, but I do know there was a negative ground on the firewall next to the MAP sensor. Upon inspection of my jeep, this is what I found:


Of the 4 positive wires, one was connected to the alternator, one was connected to the starter solenoid, one to the positive relay (I think that's what it was) and one with a fuse to a black box on the passenger side fender. Not sure what that box is.


Of the 3 negative wires, One was connected to the passenger side wheel well, one to the starter motor, and one seems to go into the passenger side headlight assembly. I will be taking the head panel off tomorrow but I assume this is the fender ground, albeit badly corroded.


The firewall ground had nothing attached to it, and I don't think the other three negative ground locations were factory. So I guess my question is, should I put the wires to their factory ground locations (wherever they may be) or just attach them to where I found them? I've upload pics as well for reference:













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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.

All the components listed below ground at the dipstick tube stud:

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the 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. If the whole stud turns, you can use a 7/32″ six point socket or wrench to hold it so the nut can be removed. Worst case, cut the wires and remove the stud and nut. Install new terminal eyelets on the wires when going back together.  Scrape any and all paint from the stud’s mounting surface where the wires will attach. Surfaces 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. Apply a liberal coating of OxGard, which is available at Lowe’s and other stores. Reinstall all the wires to the stud and tighten thdipstick stude 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, apply OxGard, 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 its intended use and subject to corrosion and poor connections at each end.

  • 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. Apply OxGard. 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 with a liberal coating of OxGard.

2 STRONG suggestions regarding the ground system:

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 tail lamp 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.  Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply OxGard also.Fuel Pump Ground Comanche

If you want to UPGRADE YOUR GROUND AND BATTERY CABLES with custom made parts, contact Paul at www.jeepcables.com 

Neal's cables

Revised 02/04/2017


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20 hours ago, motownXJdad said:

sounds about right, but there should also be a heavy ground to the engine block itself in the general area behind\in-between the AC compressor and alternator.

So I pulled the head panel off today and besides finding out the lighting harness connector was corroded just as cruiser said, it seems the wire I thought was the fender ground was actually a ground for one of the headlights???????? It was connected to an orange cap. So that means I only have two negative cables attached directly to the battery, one on the passenger wheel well and one attached to the starter motor itself. I have no clue where the third one is and I'm not sure where I should look


I also believe I found where the ground should be for the battery- engine, attached pic cuz I'm not completely sure....



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23 hours ago, cruiser54 said:

Those grounds are gross!!

The places you have circled are fine to use. 

Correct me if I'm wrong, but from your tips and watching a nickintime cable installation video I have deduced the following:


There should be one negative cable going to the chassis, one negative cable going to anywhere that is solid metal on the engine block, and finally a cable going to the fender.


For the positive connections, there should be one cable going to the positive relay, one cable connecting the alternator to a fuse, one cable connecting the fuse to the positive relay, and one cable connecting to the starter solenoid.




Negative cable queries:

My jeep only has 2 direct connections to the battery, one is connected to the passenger wheel well below the positive relay, and one on a bolt underneath the starter. It's a weird place, but I'm assuming its acting as the "block-to-battery" connection. I cannot find a third negative cable on my jeep. Since I cannot find a third connection, I am assuming I am missing my battery-to-fender ground, as I would think the wheel well connection counts as a chassis ground. The only reason I possibly cannot find a third connection is that it is in a hard to reach spot connecting the firewall to somewhere on the engine block, similar to nickintime's video.


Positive cable queries: 

All 4 positive cables on my jeep were directly connected to the battery. The nickintime installation video shows only the relay and solenoid have a direct battery connection. According to google, a relay lets you use a lighter-duty switch to run things that have a more demanding power draw. So in lieu, I'm confused as to why the previous owner didn't connect the alternator to the fuse directly. Also, the fuse went from the battery to a black box on the passenger fender. I have no idea what that box is, pic attached.


Also, your tip states the block-to-battery ground should be on the bolt just forward of the oil dipstick ground, and the oil dipstick ground is NOT supposed to have a direct connection to the battery, right? I think my confusion is stemming from the fact that this could be a "more than one way to skin a cat" situation; my cables may not be how everyone else's are but still work just fine. Or maybe I'm completely wrong.


I apologize for asking so many questions, electrical stuff was never my strong suit and I don't want to put a cable somewhere wrong and then not have my jeep turn on.




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Your negative cables are okay. The one for the block was put on a starter mounting bolt? If so, move that to the bolt hole forward on the block. The 3rd ground is the 3 or 4 small wires with eyelets at the engine dipstick stud. all else you need is a smaller gauge wire from neg bat to inner fender.

Need more pics. PO mighta been a hack.


Factory had no fuse to alternator. Pos bat to relay and another from that terminal to alternator. 

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  • 2 weeks later...
On 7/14/2022 at 10:31 PM, cruiser54 said:

Your negative cables are okay. The one for the block was put on a starter mounting bolt? If so, move that to the bolt hole forward on the block. The 3rd ground is the 3 or 4 small wires with eyelets at the engine dipstick stud. all else you need is a smaller gauge wire from neg bat to inner fender.

Need more pics. PO mighta been a hack.


Factory had no fuse to alternator. Pos bat to relay and another from that terminal to alternator. 

Alright, stupid question. I'm installing the jeep cables upgrade kit tomorrow and was curious if the jeep will turn over without the headlight harness plugged in

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