Originally Posted by xj_maniac_newb

So the engine turns over fine? Sounds more like you have connection issues/ bad alternator. Try pulling the negative battery terminal while the engine is running. If your alternator is bad then it'll go dead in a few seconds or so.

Also.. your battery could just be bad. Go have the battery checked at your local auto parts store.

Originally Posted by wesleys1990xj

What connections should i check?

Originally Posted by xj_maniac_newb

Body side ground coming off the battery terminal, as well as the battery terminals themselves. But if you have low voltage then it sounds like your battery is bad, not too small. However you could fit a bigger battery in there if you wanted. I've got a size up battery in mine, its a tight fit in the tray, but it does fine.

You're alternator could still be bad, i know plenty of people who's replaced they alternator and gotten a dud. Go to the parts store and have the battery checked first. Its probably bad.

Originally Posted by xj_maniac_newb

So the engine turns over fine? Sounds more like you have connection issues/ bad alternator. Try pulling the negative battery terminal while the engine is running. If your alternator is bad then it'll go dead in a few seconds or so.

Also.. your battery could just be bad. Go have the battery checked at your local auto parts store.

Originally Posted by cruiser54

Start with these 2 things. Cheap and easy.


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


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

Originally Posted by xj_maniac_newb

So the engine turns over fine? Sounds more like you have connection issues/ bad alternator. Try pulling the negative battery terminal while the engine is running. If your alternator is bad then it'll go dead in a few seconds or so.

Also.. your battery could just be bad. Go have the battery checked at your local auto parts store.

Originally Posted by RTorrez1

You really should stop recommending this. I have seen a few pother post that you have told this to and it the WRONG thing to do on any vehicle with a computer in it. It was fine for older vehicles before they start putting in the computer to control everything. All you are doing is leading someone in the wrong direction and possibly damaging the electronics. No it wont always cause damage but why would you want to rick it??? Like I mentioned in another post that you recommended this. You should only recommend this if you are willing to take the responsibility for frying there computer and you are willing to replace it for them. Other wise you need to stop telling everyone to try this!

Originally Posted by wesleys1990xj

Ya im not gonna do that. But i cleaned the two grounds on the block. Then i followed the alt charging wire to see if it was good, and it went from a 6 or 7 gage wire to a 9 gage wire. So i cut that 9 gage wire out, then connected it where it was in the first place,and i can tell its charging better. So now right when the headlights get dim i hear a click under the driver side dash. Maybe my headlight switch? Or maybe the connections to the switch are bad. But they don't get as dim.

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Originally Posted by 5-90

DO NOT DO THIS!

Fine with pre-74 vehicles (points & condenser, next to no electronics,) but this can lead to a huge repair bill with vehicles that have more modern electronic controls!

I've posted a writeup here on how to check your primary electrical setup - search it up and follow that. (No, I didn't keep a link. It's its own thread, so it should be easy to find...)