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 th
e 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.
If you want to UPGRADE YOUR GROUND AND BATTERY CABLES with custom made parts, contact Paul at www.jeepcables.com
Revised 02/04/2017
Great post; thx for all the tips; much needed Rx for my 90xj.
I refreshed the dipstick tube stud grounds today; was expecting only sensor grounds at that stud. Surprisingly, the battery negative cable was grounded to the dipstick stud along with the sensor grounds (battery cable not attached to its own stud).
If this is a mod then it must have been done by a Jeep service tech which makes me think it might be okay or maybe even advisable (I didn’t make the change and I’m the original owner).
Have you heard of this mod before? Is it okay to leave the battery cable co-grounded with the sensor grounds on the dipstick stud?
That’s perfect!!! Clean it and leave it.
Thank you. I cleaned it and left it. Today I followed your second “suggestion” and added a 12″ ground cable between the battery negative bolt and the closest 10mm radiator support bolt.
With my sensors and battery already co-grounded at the dipstick, there’s now a much more direct and irresistible ground path to the chassis for the sensors. TPS ground resistance measured at the connector dropped by nearly 1-Ohm from 1.7 to .8-Ohms; I’m jazzed! Thanks for the great suggestion.
Excellent.
Hello Cruiser54
These past week my grandpa Had given me his old “1987 Jeep Comanche 4.0l (Renix) 2wd base” And Ive started to work on it and read countless forums of information on problem troubleshooting and tricks for my old jeep, And I was wondering if you could possibly help me out I have a million questions, And a handful of problems with my Mj. By any chance is there an easier way to contact you directly? I dont mean to bug but from reading it seems you would be the best option for the problems that I’m encountering.
Ok Problems right off the bat, (Mind you this Mj has been sitting for 19+ years in California desert climate)
-No Power to gauge cluster
-Fuel tank is filled with gas sludge (Will probably need to be replaced) *Fuel sending unit already replaced
-Injectors dont seem to be pushing fuel *Has fuel pressure
Items to be replaced-
-Vacuum lines
-Ccv hoses damaged
– Wiring dry rotted aswell more hoses also dry rotted
– Oil changed With oil filter
– Seats reupholstered
– Set of tires
– And a million other miscellaneous stuff
I have a wrecked 1995 Jeep Cherokee sport aswell with the HO Motor and all the bells and whistles for parts.
From the information I gave and more information I can give (Plus countless photos I can send) Would you be able to help me troubleshoot these issues ?
Im just a 17 year old kid, Who’s fairly new to actually working and troubleshooting a vehicle but Im a quick learner And will do anything to get this MJ on the road again.
sure. Use cruiser54private@gmail.com
New here and you have a ton of great info. How do I sign up or did I just do it
I don’t really have a way for you to subscribe. Just come on by and look around. Post any questions you may have.
Wassup Cruiser, thank u for all of the information u have shared. You should get a Nobel prize for literature for this for realz…I have a 95 Jeep Cherokee Country. I recently upgraded to led headlights and then decided to go ahead and upgrade all of interior and exterior to led as well. I noticed that when I have my headlights off my side marker signal lamps beside headlights work great but the same bulb when signal isn’t on are dim on both sides. But when I turn headlights on they go out. If I pull the bulbs out and turn them around they do the exact opposite, dim while blinking bright while not.(The lights under headlights works great on both sides with and without headlights on) I am pretty sure that it has to b a ground issue to turn signals but the side marker bulbs only have two wires rh tan and blue/red stripe lh is green and blue/red stripe. If I’m not mistaken blue/red striped is park lights and the tan and green are the turn signal wires. So do the side marker/park lights work off of the other park light grounds or am I missing something. Any help would b greatly appreciated. P.S. I have already changed out to an electronic flasher, they actually blink a lil slower than normal to b honest. Thanks in advance!
the bulb sockets for the front turn signals get wonky. Try cleaning that old factory grease out of them.
hey cruiser54, ive been buggin you with some questions lately hope that is alright, i have only about 2 weeks left to fix and recheck all these points so im making a hurry on it 🙂
ive added an extra ground from the negative battery terminal to the radiator support bar bolt 10mm. by looking up the part number you mentioned to get at Napa https://www.napaonline.com/napa/en/p/MPB781115/MPB781115_0196438759?interchange=1
this cable at Napa looks A LOT thicker than the one i have installed, i believe the one i installed is 10,12 or 14 gauge its hard to see but i count 18 strands in this wire.
will this give any trouble does it have to be as thick like the one from Napa ? will the current take the shortest way and use this wire now to start and eventually give troubles cause it might be too thin ?
marc
I am so put out by my comanche these days..1989 renix 4.0 auto. I have replaced coil..plugs..wires cap and rotar…new battery refreshed grounds..oil change..filters serviced transmission..UUUgghh! finally driving fine on way home and started spitting and sputtering…almost like a backfire up through the manifold…slowly loosing power get it home and each attempt to restart and simply quit wont start at all…replaced the CPS,TPS..new CPS only shows maybe .2v at crank. weak spark..I need help any suggestions..rail has fuel..starting fluid nothing..
I wanted to add That I did remove the thermostat for one day until my pump came in…could that of caused a problem with the temp sensor???? Im frustrated as H#$% and don’t wanna kick any more dents in her since maybe it’s just bad mechanic. Cruiser if anyone can help it’s you sir??
Wow. Lots of stuff done. So, there’s an orange spark instead of a crisp blue one at the plugs? If there’s any spark at all, the CPS is good enough. Too bad you didn’t drill it before you installed it though.
I’d be suspicious of the coil/ICM. No real good way to test them though. Tip 4 might be worth doing at this point.
thank you for responding this now is a mission if it turns out simplicity ..New coil by the way strong spark going to middle point..made me drop it quick…at this stage I guess fuel pressure or maybe injectors??? although there is fuel at rail..even after starting fluid will not fire for even a second
new CPS and I will drill it if you think that might help just the actual holes on the sensor itself correct?..but out the box “NAPA” only reads 2v. i appreciate your time Cruiser your the man.. real quick does the CPS connector from the harness have any power coming from it? it reads a flat 0 .
CPS itself is an aC generator of sorts. So, no power TO it. Only FROM it while cranking.
Have you checked for sprtk at a plug?
Hi Cruiser. I swapped a ’98 4.0 into my son’s ’90 XJ. Tranny stopped shifting. He has to shift manually now. I suppose this ground would influence the shifting? All I’ve done thus far is adjust the TV cable and TPS. Is/are the grounds a single bundle of wires or several individual wires? What should I look for?
Thanks, Scott
Scott, if you didn’t get all of the ground wires on a clean and shiny dipstick tube stud, the TCU may not have a ground. Tip 1 details the grounds at that stud.
I’m embarrassed to say but I didn’t pay any attention when I removed the original engine. Are there multiple wires that go to that stud? I’m wondering if I missed one. I understand about ensuring good contact. Thanks.
Yes. Multiples. 2 or 3 terminals with black wires. Poke around the trans dipstick tube and see if you missed one.
Thank you Cruiser.
You are welcome. Let us know what you find.
Hi Cruiser 54, I have a 89 Jeep Comanchee and I have been having electrical problems with it , it started with the alternator gauge showing down about 9 volt and the rest of the gauges going crazy , the heat gauge would bottom out all the way to the right when I would turn or sometimes when I hit a bump in the road, the oil pressure gauge would show low pressure and the head lights would flicker and dim out. The other day while driving it it started this again and stalled out , I noticed smoke coming out from the rear left wheel well and assuming the brake might of been to tight I felt the brake drum only to find it was cool , upon looking under the rear I seen the emergency brake cable was so hot the plastic was melting off the outside of it and about to catch fire, luckily I was by a creek and dowsed some water on it to cool it off and prevent a fire , few min later the gauges went back to normal and it started but the radio and gauges would act up off and on going down the road . First chance I got I took out the dashboard looking for some type of short only to find nothing that I could see but I did noticed while looking under the hood the body to engine ground strap was melted in two and I replaced it and it seemed to fix the problem with the gauges but I noticed the headlights would go dim in sinc with the flashers or turn signals when on but the gauges seemed to work and r
the radio stayed playing on the way to town and back.
Next day I started it to go to town again and a few hundred feet down the road the truck stalled and there was smoke coming up the trans tower into the cab and I noticed had lost pedal to my clutch , few mins later the smoke cleared and it started but I had no clutch so had to limp back home starting it in 1st gear and not using the clutch . Upon looking at the clutch problem I seen the hose going to the slave cylinder had a leak and looked like it was caused by the metal end getting too hot ,so I replaced it only to find the slave cylinder was also leaking like the heat had affected it also . I’m having a big short problem where I can’t seem to find but it is not blowing any fuses or fusible links but keeps melting things like the brake cable and the clutch hose and slave cyl. It must be alot of power to heat these parts and render them useless .But I can’t seem to find the short and have looked everywhere I can . Hoping someone will have some advice before my beloved Comanche burns to the ground . Any suggestions ?
This is a tough one.
I’d start looking at the area around the park brake cable and the fuel pump/gauge wiring. Did they touch?
Ive looked everywhere , and found nothing that looks grounded out or burnt on the wires, but something fried the brake cable and the clutch hose and slave cyl , yet it does not blow any fuses or fusible links , can anyone give me some advice or have the same problem in the past
This is common when there is not a good ground path from the engine to chassis. It tries to ground through components like you describe.
Ive know of melted clutch cables because engine to chassis ground straps not connected propperly. the clutch cable becomes the ground strap!
Absolutely!!
Is it 6 different cables that you’re talking about when you say: “All the components listed below ground at the dipstick tube stud:”, or just 6 components, but a different number of cables connected to those components?
I count 6 COMPONENTS in your description, but I want to know if those 6 components are grounded through 6 CABLES (or less) at the dipstick tube stud (because someone who I hired to do the ground refresh told me, “There were only 4 wires and the ground cable (5 total) for the battery connected to that stud at the oil dipstick, not 6”).
Here’s the 6 components I’m reading in your description that ground at the dipstick tube stud (please let me know how many cables that sends to the dipstick tube stud):
1. Distributor Sync Sensor,
2. TCU main ground,
3. TCU “Shift Point Logic”,
4. Ignition Control Module,
5. Fuel Injectors,
6. ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal.
Thanks!
Ted
There are not 6 cables there. Only 3 or so depending on the year. But, all those components are grounded through those cables.
I am chasing a no start/no dash power issue. The Jeep ran fine when I pulled it into the garage this spring. I have checked and up graded all the grounds above. Anything that could cause a sudden loss in power to dash? I checked all the fuses I could find and all check ok. 90 Cherokee.
No dash power meaning none of the indicators/gauges come on?
If so, I would suspect the ignition switch.
Yes, no lights no nothing to the dash. Jeep will crank but not fire, fuel pump does not kick on.
Has anyone monkeyed with underdash wiring?
the Jeep has 256k on the clock and 5 previous owners, some of the under dash wiring has been monkeyed with what and where i can not tell. I have not messed with anything, it ran fine then wouldn’t start after it sat in the garage.
This is gonna be a tough deal. You’ll need a wiring diagram and lots of time.
I have a 87 XJ. I have upgraded the battery cables and grounds with 2awg. The wire that ran from the alternator to what looks like a fuse block behind the battery did not have a fussible link in it. Should it have had one? Should I install an ANL fuse in between the two?
Yes. It should be fused.
I thought it seemed odd. Big thanks man.
Cruiser,
I’m having a no key on power problem. I pulled the ignition switch, noticed that the brown wire (for the blower motor I assume) was burned but still making good contact. I installed a new ignition switch. Then after charging the battery which was dead after i replaced the switch, it started and ran decent. THEN, I turned on the heater/blower again and it died immediately. Same no power with key on. The blower fuse is also burned up really bad.
I checked the battery voltage, refreshed grounds, bigger head/firewall ground, c101 eliminated. Aft
I have 12v+ at the red wire and am getting 12v to the green wire going to the starting solenoid (when I bridge the red and green wires, it will crank.) but when I plug in both the connectors to the switch, it will not give power in the key on, acc, or start positions. Headlights/running lights are working. Brake lights working.
Getting extremely frustrated with this problem. Need some help where to start diagnosis.
Sounds like something else got melted and shorted into some HOT wires during the initial issue.
It ended up being a combination of problems. Just my luck. After eliminating c101 and connector refreshing, I found that my blower motor had caused the initial problem. There was significant corrosion on the BM ground and I replaced the motor for insurance. Then when i unplugged the connector that passes through the firewall to the fusebox, i inspected each pin and found that one wire had come uncrimped over time. After soldering the offending wire, cleaning the connector, followed by oxgard, she starts reliably every time.
Excellent job!!!
You’ve seen the Tip on improving the BM ground?
Does the TPS ground at the dipstick stud also?
Yup. Through the ECU first.
Thank you.
Hi Cruiser54, I have caught up with all the grounds upgrades now. Regarding a similar electrical topic, I recommend “Greg Smith Power door locks” at https://naxja.org/forum/showthread.php?t=1874. A schematic is at: http://www.jeeptuning-foto.com/albums/userpics/10010/two-relays.pdf
You have to be methodical, but the schematic helped alot! This finally fixed what’s been a real bother I’ve struggled with for years! Rick
Love your site! You’ve been a gold mine of information! Want to pick your brain again. My 1990 dies randomly. Usually starts right back up again but once it starts doing the dieing thing it’ll happen multiple times. Sometimes it doesn’t want to start right up. Occasionally going down the freeway it’ll cut out for a split second, the tach drops to zero, then it keeps running. My cps connector had a lose pin, fixed that and it ran fine, no problems for several weeks. Now it’s back again. Checked cps connector, it’s tight. Checked cps voltage and it’s .43-.46. I think I’ve done all your other tips. Double checking the icu/coil connections now but they look ok. Any ideas? Thanks.
The tach dropping points to CPS and ignition control module. Have you refreshed the connectors on the ICM?
check your CPS harness routing also.
I refreshed the icm/coil connections and rerouted the CPS harness behind the head to the stock clip on the valve cover. That solved 98% of the problem! Drove it for a week with no issues then 2 times on the freeway it had what felt like a complete misfire but only for a split second and no tach drop. Decided to fire a parts cannon volley and replaced the cps (covered the wire with spark plug wire heat guard, did the cps advance tip and enlarged the upper hole tip), routed the wire as far from the exhaust as possible, replaced the coil and icm. Figured the coil and icm are 30 years old with 327,000 miles that it was time! The icm still had the “made in France” sticker on it! . Now it seems to run just fine, maybe a touch better than before. Next is the distributor to replace, it recently started a squeak occasionally, any recommendations on brand?
Great job Kevin!!
It’s hard to recommend a brand of any part these days. So many chicom knock-offs. Maybe your local Napa?
Don’t forget the o-ring mod instead of the gasket, and then index it properly. I bet you see even more performance.
These are great tips especially for an XJ newbie. I’ve done the ground fixes and have less than .1 ohm read with a 4 wire ohmmeter. My Snap On brick says ECU voltage is 13.5-13.8 but voltage at the battery is 14.4. Is that to be expected or is C-101 cleaning in order?
Thanks for your great site!
c101 cleaning is ALWAYS in order!! Elimination is best. That said, it’s normal to see a voltage difference.
89 Cherokee with the 4.0.The only ground I have near the dipstick is the battery ground. There are 2 other grounds on the same stud. Where else could mine be?
That’s pretty common. clean em up!!!
Thanks. I already cleaned them. My question is actually what other grounds should have been there and how can I locate them?
They varied in configuration over the years. first place to look is back at the loom where the ones you have found originated from. It’s a total of about 4 wires.
Hey Cruiser do you recommend replacing the braided cable ground on cylinder head with #4 cable?
Absolutely! You can even leave the braided and run #4 from the firewall to a bolt on the intake manifold.
Watch that braided cable. Prior owner had engine replaced, shop of course had to remove then re instal that cable, they routed it over the wire bundle rather than under it. vibration caused the braided cable to cut into the wire harness! braided cables and braided hoses act like a hacksaw when vibration moves them around, be aware of this! Route that cable carefully, do not allow it to rub on the adjacent harness!
Hi Cruiser, having some issues with an ’89 Cherokee that are puzzling. I was in process of installing a new set of fog lights and the red wire to the 10 pin connector for the front lights had gotten rubbed bare and grounded out to the core support, after replacing that wire, checking the fuses, grounds, etc. Im stumped. The Jeep starts and runs, but brake lights, running lights, head lights, fog lights, and radio all dont have power.
Check for a burned fusible link at the solenoid/relay on the right inner fender. Right next to the bank of 4 relays.
when you say “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 you say”
you are talking about adding the ground to the existing ground strap at the firewall right?
Yes
Do the Jeep cables MJ “big 7” include your Napa grounding hacks? Didn’t feel like buying them off the kit already included it. Truly awesome page by the way!
The Big 7 has it all covered. My “hacks” are just a simple upgrade for the average guy or gal.
Hey Cruiser, loving these tips. Thank you for this. My 88′ Comanche was developing the infamous “starts then immediately dies” problem. Long story short, it was a bad fuel pump ground. Fixed after completing the latter parts of tip№1. Ive already moved on through the next few. Just awesome knowledge. Thanks for passing it down.
I have a question; why are some of the last tips in your series removed? It’s like the links have been removed. Example: running an open cooling system. Just curious.
those are not removed, just never written. LOL
Hi Cruiser54,
I’ve done most of the ground improvements you suggest on 92 XJ 4.0 L.
However I did read somewhere about a ground improvement to be done in the driver-side foot well, behind the side panel I believe. Unfortunately when I searched again, I couldn’t find this post anywhere, and I haven’t seen it if your list of suggested improvements.
Does that ring any bell?
Best regards
Pascal
tip 18 is what you’re looking for.
Just wanted to throw this out there because it caused me a massive headache and a bit of prevention could save someone else down the line.
On my ’89 Cherokee 4.0, auto trans all six fuel injector grounds, and three other ground wires (One is for the IAC, the other for the square plug on the TPS, the third I havent chased.) splice into two wires which go to the dipstick stud. The splice is very similar to that of the sensor grounds in tip 6 (awful and covered in 34 year old duct tape). Yes, 9 ground wires, spliced into 2, which meet at the same groud point. Quite the recipe for disaster. If you are having issues with weak, intermittent, or no fuel injection pulse then start here before paying for an ECM, this splice failing can also cause a lack of voltage at the square connector of the TPS, and the IAC.
I’m commenting here and not on Tip 6 because despite having to open the wiring harness for both, my recommended fix is to remove the two wires at the dipstick stud end, delete them entirely (because two wires spliced into 9 is ridiculous) pair the injector and other ground wires in pairs of 2 or 3, add heatshrink, splice and solder them into one 10ga wire per bundle, add a ring terminal to the end of each and reattach to either the dipstick stud or the stud on the block a few inches forward of the dipstick stud. The dipstick stud is the more efficient grounding path, but it can get a bit cluttered and hard to install/remove by adding another 3 or 4 ring terminals. You can also add a 4ga jumper from that forward stud to either the battery negative or to the dipsick stud if you want a bit more redundancy on that circuit than grounding straight to the block. If there’s one thing the last few weeks of Renix induced headaches have taught me is that the more grounds the merrier and to oxgard everything.
Ideally you should perform tip 6 while youve got the wiring harness opened up if you haven’t already, as well as check for, and repair any other wiring issues as well. Probably a good idea to resplice and solder any other duct tape covered nightmares you find in there as well. 34 years is definitely past the expiration date of those old splices.
Crusier,
New to me jeep, put a fuel pump in and it started up.
Idles pretty decent, but anything off idle is massive back firing out the exhaust, chugs in drive off idle, until about 80% throttle, then it runs great! Free revs good unless you go slow.
Tps set
Sensor grounds are .4
New coil, plugs, wires, fuel pump, and distributor.
Cleaned idle control valve next to tps
All vaccumm line have been traced and look good and going to the proper areas
Make sure the intake manifold bolts aren’t loose. Also, the vacuum hose to the MAP sensor may be compromised. Melted. cracked etc.