My '88 with the #1 cylinder problem was really bugging me because on top of the rough idling, it would decide not to start every once and a while-usually right when I wanted to test something out. Well, I was looking at some of the horrible wiring and started working on the C101 connector (full of tar like Cruiser said). I put that back together (not completely cleaned out but better) and then the Jeep wouldn't start. Mad. Left it for a hour, came back out and it started fine. Ok, went to clean up wires on the passenger side with a zip tie. Moved a wire and the engine stopped. Huh? Key was still in ignition in run and I started to move the wires near the dipstick ground stud. Fuel pump relay clicked off and on. Wow. Took all the crap apart (PO had a lot of splices in there) and there were 4 grounds to re-connect. I sprayed degreaser and scraped the block and the dipstick bracket and cleaned up the bolts. I made a short bus-bar to bolt the too-short groundwires to the bus-bar and then ran a nice big piece of wire to the cleaned up ground. Jeep started right up. Checked it again an hour ago-Fine again. So I'm hoping this was the culprit. I still have a new CPS to put in but I'm wondering if it was a bad ground all the time.

BTW - that bolt is hard to get back in while trying to hold wires, bracket and wrench all at the same time. I got pretty dirty but it will be worth it if that was the big issue.

Now to try a new fuel injector in Cylinder #1!

 

More than likely. If you own a Renix Jeep and ignore the ground refreshing, you're asking for trouble down the road. Just like not checking the sensor ground issues and cleaning a C101 if you have one.

That's why I wrote this:

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 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.
　
　
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 11-28-2011

 

Yes-That's what I did-Great posting. There were 4 black wires plus the battery negative on that stud. Does that sound about right as for the number going to it?

Looks like my Jeep got a little hacked up electrically-apparently there's a remote car starter hooked up but no idea if it was working. Lots of splices.

Thanks for your help.

 

3 or 4 wires at the stud. Sometimes the negative cable is attached there or further forward on the block.

I've seen the studs loose in the block, too.

 

Yeah-I did see another potential threaded hole forward from that one. Just gave it a try again and it started fine. Normally, I was getting about 50% success having it start so i'm thinking this was the issue.

 

I actually prefer having the negative cable at the stud if I can. If not, a cable from the stud to the passenger inner fender stud by the shock mount.

 

I re-read your instructions. I put the negative battery cable and the cleaned up wires back on the stud together by the dipstick. That's where they were on my Jeep when I took the bolt off. Is the stock location to have the battery negative on its own stud and the smaller wires from the harness on the dipstick stud?
In retrospect, it would be easier to have them separate since it was hard to maneuver all the wires and hold that dipstick bracket and put the bolt through everything.

 

I believe they normally have the negative cable further forward on the block.