Jeep Driver Posted August 2, 2018 Share Posted August 2, 2018 Two years ago I replaced my fuel pump with a Bosch. At the time I complained that the pump was slow to respond and remained sluggish, I referred to the pump as a POS. Pump would slowly prime to 14lbs but when throttle was applied it would dip down to 10-12lbs. Cab forward, I have gone through most if not all the wiring- Head light harness C101 delete. New cables, new grounds. Eliminated all unnecessary wiring. Aftermarket ignition switch. New fuse block. New alt, new starter, new ignition module (NOS).........etc..etc....etc............. Still have more to do, aftermarket gauges, existing gauge wiring will be modified or removed. Still have to wire the amp and so forth. The only wiring that I have not gotten to was the rear, tail lights and fuel pump. Bed is coming off for paint, new tail lights, and I will rewire for trailer brakes/lights and peekaboo back up lights. Back to the fuel pump- Last weekend, after reading of some of the complaints here, I decided to remove the taillight and look at the G107, I've been aware of it, just never bothered. Here- Not only was there common corrosion around the sheet metal screw (no rust) but as you can see the corrosion runs deep into the wire. I ran a new ground temporarily to a ground post at the rear. Pump now primes immediately and will hold 17lbs regardless of throttle. Pump is now running as it should. More here- Anecdotal? No, Jeep wiring is notoriously for $#!&. Why my post? Currently, page one- No start. Strange blinker. Battery overheats. Radio pops. No back up lights. Wiper speeds. No spark. Horn relay. Same questions, same causes, same answers. If you have not gone completely through your wiring, you need to. If you are not comfortable, take it one wire at a time. But look at the big picture, otherwise, you'll spend all your time chasing one problem after another. Link to comment Share on other sites More sharing options...
cruiser54 Posted August 2, 2018 Share Posted August 2, 2018 1 hour ago, Jeep Driver said: Two years ago I replaced my fuel pump with a Bosch. At the time I complained that the pump was slow to respond and remained sluggish, I referred to the pump as a POS. Pump would slowly prime to 14lbs but when throttle was applied it would dip down to 10-12lbs. Cab forward, I have gone through most if not all the wiring- Head light harness C101 delete. New cables, new grounds. Eliminated all unnecessary wiring. Aftermarket ignition switch. New fuse block. New alt, new starter, new ignition module (NOS).........etc..etc....etc............. Still have more to do, aftermarket gauges, existing gauge wiring will be modified or removed. Still have to wire the amp and so forth. The only wiring that I have not gotten to was the rear, tail lights and fuel pump. Bed is coming off for paint, new tail lights, and I will rewire for trailer brakes/lights and peekaboo back up lights. Back to the fuel pump- Last weekend, after reading of some of the complaints here, I decided to remove the taillight and look at the G107, I've been aware of it, just never bothered. Here- Not only was there common corrosion around the sheet metal screw (no rust) but as you can see the corrosion runs deep into the wire. I ran a new ground temporarily to a ground post at the rear. Pump now primes immediately and will hold 17lbs regardless of throttle. Pump is now running as it should. More here- Anecdotal? No, Jeep wiring is notoriously for $#!&. Why my post? Currently, page one- No start. Strange blinker. Battery overheats. Radio pops. No back up lights. Wiper speeds. No spark. Horn relay. Same questions, same causes, same answers. If you have not gone completely through your wiring, you need to. If you are not comfortable, take it one wire at a time. But look at the big picture, otherwise, you'll spend all your time chasing one problem after another. Let's go a step further..... The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, and behind the driver’s taillamp on an MJ. Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture. Locate the black wire on the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire. Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.Solder the connection. Tape it up and reinstall the split loom covering. At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces. Revised 1-31-2016 Link to comment Share on other sites More sharing options...
cruiser54 Posted August 2, 2018 Share Posted August 2, 2018 This is a good one to do, along with the blower motor and wiper ground upgrade. The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release knob. The screw will have either a ¼” or 5/16″ head on it. This ground point is responsible for handling the ground circuit for the following items: Dome lamps, seat belt and key warnings, transmission power/comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things. The problem is that where the ground point is located does not share good contact with the chassis where the ground should be. The solution is simple: Make up a jumper wire with #10 gauge wire about 10″ long. On one end, crimp on a ¼” round wire terminal. On the other end, crimp on a 3/8″ round wire terminal. Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other. Look above the driver’s side plastic kick panel just forward of the top of the hood release knob. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely. Use a coating of OxGard at all ground contact surfaces when attaching the screw and nut. **Special note for Comanche owners: Make your jumper wire 12″ long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.** Link to comment Share on other sites More sharing options...
cruiser54 Posted August 2, 2018 Share Posted August 2, 2018 On 87 to 90 MJs and XJs, the blower motor’s factory grounding point is on the driver side inner fender under the sheet metal screw. This ground is shared with windshield wipers, front windshield washers, rear windshield washers, AC clutch relay, fan control relay, fog lamps, fan motor, headlamps, front turn signals, front side markers, and park lamps. So your blower motor has its ground point 10 feet away from where it is located!! What we’re going to do is leave that ground intact and also ground the blower motor on the passenger side inner fender much closer to the blower motor itself. This will also benefit the other components on the factory ground circuit. Take this opportunity to refresh the factory ground as a matter of course. Remove the screw, scrape the surface to bare metal and reinstall the screw securely. Here’s what I do to get the ground much closer to the blower motor and add another ground point to this overloaded ground circuit. Find the blower motor connector on the passenger side. Red and Black two wire connector. Find a location where the black wire can be made to reach the passenger side inner fender, and cut the wire. You may have to do some rerouting of the harness to achieve this. Take both cut pieces of wire and put them together into a yellow eyelet and crimp. Fasten the eyelet to a place on the passenger side inner fender with a sheet metal screw after applying OxGard to the contact surfaces. Be sure to scrape the attaching point on the fender to bare metal first. Your blower motor will now turn faster and last longer, and the other electrical components on the circuit will benefit from a better ground path. Link to comment Share on other sites More sharing options...
ratty Posted August 2, 2018 Share Posted August 2, 2018 Good info. Thanks. I have a lot to do still. Link to comment Share on other sites More sharing options...
Pete M Posted August 9, 2018 Share Posted August 9, 2018 bump for great info! Link to comment Share on other sites More sharing options...
cruiser54 Posted August 9, 2018 Share Posted August 9, 2018 Here's the current Tip content at www.cruiser54.com There are also a bunch of links on the home page. INDEX Cruiser’s Mostly Renix Tips Technical DIY instructions covering common issues on the Renix XJ Cherokees and MJ Comanches (1987-1990). Preventative and proactive procedures to save you headaches, time, and money. Many of these tips were provided to me and my buddy Joe by JeepTech when I was Service Manager/Shop Foreman at a Jeep dealer from 1980 through 1992. That’s what “The Book” is all about. Our notes from back in the day. Right from the Field Service engineers. Thanks Lonnie and Big Al!! Most were never published, until now. Tips 1 through 5 are a great place to begin before chasing your tail with parts replacements on your 87 and 88 Jeeps. These are pretty much “haftas” in Renix Jeep ownership. You can skip Tip 2 if you have an 89 or 90. But, do the Tips first……….Avoid firing the “parts cannon” at your Jeep!!!!!!! The next priorities are Tips 11, 13, 31, 25 and 26 A simple multimeter is handy along with a few other basic tools……so dive in and get to know your Renix Jeep. Some Tips also transfer to later years, or the techniques can be adapted. 1 – Ground refreshing 2 – C101 connector refreshing 3 – Connector and relay/receptacle refreshing 4 – Coil/ICM contacts 5 – Checking sensor grounds 6 – Sensor ground upgrade 7 – CPS testing and adjusting 8 – TPS testing and adjusting 9 – ECU connector refreshing 10 – Trans plug connector refreshing 11 – Throttle body and IAC cleaning 12 – Setting your 4.0 to #1 TDC 13 – Renix Distributor indexing 14 – Restoring Throttle Butterfly Adjustment 15 – Rear main seal diagnosis 16 – Vacuum test for exhaust restriction 17 – HO engine into Renix 18 – Improving the instrument panel ground 19 – Headlight harness installation 20 – 4WD shifting tips 21 – Renix EGR valve test 22 – Renix vacuum harnesses 23 – CPS timing advance mod 24 – 4.0 Engine date codes 25 – Valve cover mod ***NOW WITH VIDEO*** 26 – Oil Filler cap Mod 27 – C101 Connector Elimination ***NOW WITH VIDEO*** 28-Improving blower motor performance 29-Improving the fuel pump ground 30-Adding the Sentinel Headlamp feature 31-Throttle body to MAP hose upgrade 32-Renix metric oil filter to SAE filter 33-Converting to an open cooling system 34-Eliminating the Heater Control Valve 35-Reducing cabin wind noise 36-Bypassing the Power/Comfort switch 37-Best injectors for Renix 38-Improving the wiper motor ground 39-4.0 Engine Removal 40-More power for your 87 and 88 4.0 ***VIDEO*** Link to comment Share on other sites More sharing options...
MeanLemons Posted October 3, 2018 Share Posted October 3, 2018 Amc harnesses for the engine and the one that runs along the firewall, then past the battery, and out & travels across the front crossmember and back into drivers side and connects to the firewall has probably anywhere from 15-20 $#!&ty crimps & wrapped with duct tape without any insulation and are prone to corrosion. I had to search through those harnesses and soldered every joint I come across. Link to comment Share on other sites More sharing options...
SenorT Posted March 24, 2019 Share Posted March 24, 2019 With an '88 MJ that I had a hard time getting to start, replacing the battery cables using cruiser54's info made all the difference in the world. Good stuff. Link to comment Share on other sites More sharing options...
Jeep Driver Posted April 15, 2019 Author Share Posted April 15, 2019 Solving my ground problems for good. 1/4-20 stud welded at frame, all grounds at rear will go here, tail lights, trailer wiring, E-brake, accessories......etc. Just north of fuel tank, this ground stud is for the fuel pump and possibly the new gauge sender. Link to comment Share on other sites More sharing options...
Pete M Posted April 15, 2019 Share Posted April 15, 2019 nice Link to comment Share on other sites More sharing options...
jdwillys Posted June 16, 2019 Share Posted June 16, 2019 Great thread! Big help, I will be using all of information, thank you! Link to comment Share on other sites More sharing options...
Swampy Posted August 14, 2019 Share Posted August 14, 2019 I have been meaning to ask this question, but are all the grounds necessary to have or can I eliminate some? Like on the 2.5 there is one that goes from the head of the engine to the firewall. It doesn't seem to be connected to anything so can I just get rid of it? I just got a new wiring harness for my mj so I am going to be going through all the grounds and wiring to clean it up as much as I can and eliminate what isn't necessary. BTW anyone have mj 2.5 wiring diagrams? Link to comment Share on other sites More sharing options...
Pete M Posted August 14, 2019 Share Posted August 14, 2019 without knowing any specifics, I can tell you that more grounds is always better. I have added at least 3 to my old 88 so far just to make the thing work right. Link to comment Share on other sites More sharing options...
Swampy Posted August 14, 2019 Share Posted August 14, 2019 10 minutes ago, Pete M said: without knowing any specifics, I can tell you that more grounds is always better. I have added at least 3 to my old 88 so far just to make the thing work right. Good to note Link to comment Share on other sites More sharing options...
Pete M Posted August 14, 2019 Share Posted August 14, 2019 specifically those were: a ground right by the fuel pump, a big general dash ground right to the battery, and a new block-to-battery ground. next up is a fresh ground for the blower motor. brand new copper wires are a great path for electricity. old painted sheet metals, corroded wiring, self tapping screws, etc... not so much. Link to comment Share on other sites More sharing options...
Otg 92' banger Posted January 29, 2020 Share Posted January 29, 2020 LHello...first post here... going to put my vin in the registry in a bit. I'm wondering if comanches have dome lights? I bought my 92' with the interior already pulled and I'm about to start putting it back together, supposed to have all the peices but haven't seen a "dome" light or wires... Link to comment Share on other sites More sharing options...
Pete M Posted January 30, 2020 Share Posted January 30, 2020 15 hours ago, Otg 92' banger said: LHello...first post here... going to put my vin in the registry in a bit. I'm wondering if comanches have dome lights? I bought my 92' with the interior already pulled and I'm about to start putting it back together, supposed to have all the peices but haven't seen a "dome" light or wires... nothing in the middle, just lights in the b-pillars. there are a couple writeups on using newer LED housings in the factory location in the link in my signature. Link to comment Share on other sites More sharing options...
Otg 92' banger Posted January 30, 2020 Share Posted January 30, 2020 Thanks... I will probably be doing a lot of custom work with this as it appears to missing panels and some broken ones... Link to comment Share on other sites More sharing options...
CoastChief Posted January 30, 2020 Share Posted January 30, 2020 How’s it going everyone! Happy almost Friday. got up early with some notes from the forum. I found this unattached and could not find the proper port. any help is huge, learning as I go! Link to comment Share on other sites More sharing options...
jdog Posted January 30, 2020 Share Posted January 30, 2020 If it's a red wire it will go to the underhood light. Stock 1988 swb 4.0 ax15 np 231. Link to comment Share on other sites More sharing options...
High2by Posted January 30, 2020 Share Posted January 30, 2020 That wire just won't go away...... Link to comment Share on other sites More sharing options...
jdog Posted January 30, 2020 Share Posted January 30, 2020 That wire just won't go away...... It's a nightmare wire Stock 1988 swb 4.0 ax15 np 231. Link to comment Share on other sites More sharing options...
ValpoManche Posted April 26, 2020 Share Posted April 26, 2020 Has anyone located, like @Pete M , the ultimate places to put new grounds on the MJ? I’ll be rewiring mine as I covert to 97+ Cherokee. Just curious. Or, has anyone coated it in dielectric grease and found a way to trap the grease on the ground? Link to comment Share on other sites More sharing options...
jdog Posted April 26, 2020 Share Posted April 26, 2020 Cruiser54 knows I believe Link to comment Share on other sites More sharing options...
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