hypersthenos

Hey All. I have an '87 with a 4.0 Renix. This thing is in remarkable shape & runs great. The idle speed was a little sporadic so I added a large ground cable from the rearmost bolt holding the heat sheild to the intake manifold to the original spot on the firewall (I left the original ground strap in place). To my surprise this eliminated the erratic idle. I am now going to make my own oversize battery cables to further improve the electrical system. I'm wondering if any of the rest of you have made similar improvements and where you ran the extra ground wires. I'm planning on adding another ground cable from where the negative cable from the battery bolts to the block to somewhere on the frame (engine mount bolt?). Any other ideas/ground locations that need attention? Thanks in advance.

freegdr

i have upgraded my cables on my 89 also both negative and positive ,my idle improved,alt charges better and lights got brighter. All cables bought from napa think it was about 35 dollars for all cables

89Laredo

5-90 makes a kit.
http://www.kelleyswip.com/electric.html
http://www.kelleyswip.com/price.html

hypersthenos

That's a cool kit. Very similar to what I'm doing with #1 welding cable. From the description of the kit I now know that I need to run a ground from the alternator. I'm wondering what other ground locations should be checked/cleaned-such as under the dash or other underhood locations.

cruiser54

It's amazing what a difference that firewall ground makes when it's been refreshed or upgraded, huh?

While we're on that subject, here's the first draft:

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.
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.

hypersthenos

Great info. Thank you! Yesterday I addressed the grounds at the dipstick tube mount & found the stud loose. Everythings good there now. Of interest is that my negative battery cable is also mounted to this stud rather than forward of it as indicated in your reply. This was done at the factory on mine as there was one of those goofy grommet/washers over the connection to keep it in place during assembly. I am now getting ready to make the positive cable. I'm using #1 cable & a solder connection at the battery end with a larger lead going to the connection under the relay cover. My question is that I've read on here that the terminal end at the starter has to be re-used. Is this the case or can I make something up? I'd like to know ahead of time so I don't have it apart & need to make another run to town.

cruiser54

I like having the negative cable hooked to the dipstick tube stud!! I don't remember the starter end of the positive cable being anything out of the ordinary.

The Rooster

i think i may have to do this...

Gee oh Dee

It can't hurt and its free.

cruiser54

Anybody with a Renix Jeep needs to do this, along with a few other things I'm doing write-ups on..

hypersthenos

Thanks cruiser54. You, sir need to write a book on these Renix Jeeps. I'm glad to hear there's nothing special to the + terminal at the starter. Just caught another thread where you mentioned cleaning the pickup coil contacts in the distributor. That's my next project. Thanks again.

cruiser54

Here ya go:
Renix Jeep ICU/Coil contact refreshing
　
　
The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.
The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.
Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.
While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　

cruiser54

Here's a list of the outline and what I've written an dwhat I plan to write. Let me know if something in particular tickles your fancy.

　
Introduction 11-25-11Rev
* means instructions have been written.
　
1-Ground refreshing*
1a-Adding engine bay grounds*
1b- Link to Kelley's Works In Progress*
1c-Improving the instrument panel ground
2- Checking sensor grounds*
2a- Repairing sensor grounds*

3-C101 Refreshing*
4-Connector refreshing
4a- Relay /receptacle refreshing
5-Coil/ICM contacts*

6-Checking for vacuum leaks
6a-Snugging up intake manifold fasteners
7-Throttle body cleaning
7a-IAC cleaning
8-TPS testing and adjusting*
9-CPS testing and adjusting*
10-CPS wiring bypass
11-ECU connector refreshing
12-Distributor indexing
13-O2 sensor diagnostics

hypersthenos

Well, pretty much all of them but as I'm focusing on the electrical right now the top of my list would be repairing the sensor grounds and instrument panel grounds. Thanks in advance!

cruiser54

You've checked the sensor grounds and found higher than 1 ohm resistance?

The write-up I have is for 87 and 88 with the C101 connector. You can still use it for an 89 and 90 though, just disregard the reference to the C101.

I haven't done the instrument panel ground improvement yet, but I'll put it near teh top of the list.

Find your Intake Air Temp sensor. It's the sensor just to the rear of the throttle body, has 2 wires, and screws into the intake manifold.
Where it's connector plugs into the harness you will see that one of the wires on the harness side　is brown with a white stripe. Follow the brown with white strip wire back into the harness. You'll have to open up the split-loom plastic sheathing to follow it. It will come to a splice with 2 other brown with white wires. They're from the TPS and the CTS. The 3 wires will be　 spliced to a single wire headed toward the C101 connector.
　
Now go to the MAP sensor. Follow the brown with white wire into the harness from there. You will find a splice with 2 more brown with white wires. At the splice you will find the 3 wires connected to a single brown with white wire going toward the C101. Along with the MAP sensor that you traced, they are the ECU sensor ground port and the diagnostic connector on the passenger inner fender.
　
You now have 2 sets of 3 brown with white wires, one set on each side of the C101 connector.
　
Cut the splices out of each set of wires. You will be connecting the 2 sets of three wires together.　Solder the 2 sets of wires together and insulate them properly with tape or shrink tubing.
　
Zip-tie up your new sensor loom to allow for engine movement.　I prefer to cover it with some new split-loom or wrap it neatly with electrical tape when done.