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 10-16-2018
Not at all.
help thps mechanical/electrical non-genius. im working on a no start condition following a complete rebuild of my steering column. i fixed the column. its right, i know in my heart. ( i had extra parts after rebuild, two tjimes. i put it together 3x.) 88 xj ran like a champ prior to column rebui;d. i replaced 95 percent of the fuel system with success. after column replaced, NO START. ign. swithch good. starter relay good. ignition coil tested, good.
i began to examine the fuel pump ground. i peeled the wire and, having never soldered before, i foolishly began to solder my new ground lead for the pump. what a fiasco. trying to solder a connection, upside down, with a chincy iron.
finally, i just twisted the wire and shrunk it, feeling like i learned a lesson and id make it right later.
i put current to the circuit and last thing i saw was wires leading to the ballast resistor just pouring off their insulation and clouds of smoke. DISHEARTENING! basically, i said fudge it ,1.5 years ago. F that! i will overcome, with help.
I feel like, i put a fastener through a wire.. does that make sense?
if i melted insulation on that circuit, is the whole pathway fudged?
im not gonna let it beat me. ive fixed so much on this thang and its got low miles and purrs man, it purrs!
can somone give me vision? how should i approach this?
Appreciated! I came here from your link on jeepforum, and as I just replied there, I am wondering how to increase likelihood that this replacement pump will not fail as rapidly. was wondering if electrical ….something… might be contributing to failure problem.
will change the ground this time, too.
Gloria, a good ground for any Direct Current motor is very important to ensure motor longevity and peak performance. I have to ask what brand fuel pump you have currently installed.
I’ll be doing it either way, but have you or anyone else had any luck with this helping the notorious inaccurate XJ fuel gauge? I’ve tried two different pump/sender assemblies and cleaned the contacts on the back of the cluster with no change. I know my range, but it sure would be nice 🙂
I guess you’re now gonna be the guinea pig for that. It’s on your shoulders to report back!! LOL.
I completed the ground about a few weeks ago – it improved the sensitivity of my gauge (needle moves going around corners/uphill, never did that before), but did not improve overall accuracy (gauge still reads close to E on 1/2 tank.)
Still, can’t go wrong with more grounds! Thanks for the tip.
Progress!! Have you done Tip 18?
That may help with gauge accuracy.
Yes, I completed Tip 18 a while ago and noticed no change. Perhaps my sender assembly is just worn out, but I have often wondered if it is thrown off with modern ethanol blends/other additives not present at the time of the original design.
When u say harness side u do mean the wiring harness for the jeep under the hood don’t u? Probably a dumb question but I did the tip a while back and around that same time is when I switched injectors and new fuel tank/filter but started having trouble with jeep not wanting to idle. So It crossed my mind maybe I did something wrong with the extra ground. By the way I didn’t soldier I used but connectors.
In this case I’m referring to the HARNESS side of the fuel pump/gauge connector. The part that belongs to the vehicle, not the fuel pump. Not the side that’s part of the fuel pump assembly’s module. Under the vehicle.
I never use butt connectors. Only solder, especially in critical areas.
I guess what I mean is I know u are at the three wire plug near the fuel filter. However,. I still don’t understand which side of that plug? Would it be the black wire towards the front of the jeep or the rear of the jeep? I just went out now and looked at mine and I did the add in of the new ground on the black wire coming out of the frame. I will good back and solder soon. Wish I could send u a pic of what I’ve done.
Front of the Jeep.
I am pretty sure from ur reply I am on the correct side of the plug I just need to solder my wires.
Thanks for the help . This jeep detective work may turn me into a decent shade tree mechanic one day.
LOL. You will definitely learn from this experience. that’s the idea!! Solder away.
The pump on my 89 just went out after 518,000 miles. So I replaced it with a JY Bosch from a Renix era rig that I had as back up ( for the past 10 years) in the spare tire rim.
I have found that the OEM sensors and parts 25 years old, out perform most of the new stuff out there.
I totally agree. Good old stuff is better than crappy new stuff.
Can this ground lead to a poor fuel pressure over time?
Hard to say. A poor ground will cause the fuel pump to get hot.
I would do the mod no matter what.
Thanks for the fast reply! I’ve been working on my daily driver a 1988 pioneer 4×4. You have a great site with awesome info. I’ve done lots of the tips. Thanks for keeping this site up.
Thanks for the kind words. Keep up the good work!!
I’m trying to find a way to get a new return fuel line. The hose section. What would I use considering that part is obsolete now and is not made anymore?
The one in the engine bay?
Yes sir.
All you can do is use high pressure fuel line of the correct diameter and double clamp it at each end.
ok sounds like a project, im going to see if john deere can make me one with the connectors on it. thanks a lot! pulling my pump and the internal hose was loose so my pressure was only 21 psi and the strainer and return check valve was gone… lol jeep life. dropping the tank to fish them out! fun stuff but the wife is jealous!
LOL. You’re doing great!!
Is there a return check valve on the fuel pump assembly? If so what would the part be called I’m having a heck of a time figuring it out. It’s kind of a cone shaped black piece on the return line in the tank.
No return check valve. Are you referring to the conical piece that fits down into the tank?
Yes sir. Do I need it?
It keeps the fuel pump from making an obnoxious noise.
I spliced into the black wire, ran new ground wire to the fuel filter bolt. I did this on the tank side of the plug. 1. The fuel pump stopped working. 2. the new ground wire got very hot.
You did something wrong then.
Sounds like you chose the wrong side of the harness. I interpret the correct side as the one coming from the front of the vehicle. Example: If you were to remove your tank, you’d have disconnected and removed the tank-side end of the harness (because that “half” of the harness terminates into your pump/sender). In this case, you’d have only the front part of the harness remaining installed on the vehicle. That’s the one you splice from.
Perry, you are correct. Is that somehow not clear in the instructions?
Ever have the mj metal tank cause a short to the pump? I have two assemblies with pumps. One original to my truck since i bought it and one brand new. They run with a hot wire to the battery and hooked to the jeep OUTSIDE the gas tank. If i touch either to the tank at all. They won’t prime or run on trucks harness, or run on a seperate wire lead. Itll actually dead short the wire. But only.touching the metal tank. Otherwise it’s fine… Im not sure what this means. Here is a forum i started on comanche club.
https://comancheclub.com/topic/54840-fuel-pump-not-running/?page=2
Also i did your ground tip on the old assembly abd cleaned ground behind taillight. No changes.
Figured it out. Ground strap to tank and the pump was in wrong and shorting to tank.
Will this improve the fuel pump whine? Hoping so!
Let us all know!! Interesting idea.
I appologize if this comment is out of place for this thread. But wont know untill I post.
Did a compression test with the fuel pump relay pulled. Pump is loud but could no longer hear it after pulling relay.
During compression test I kept smelling gas even though I blead the fuel rail. After testing was finished, just for the heck of it I depressed the Schrader valve and gas squirted out.
Is there any reason why that could have happened?
Thanks in advance.
I remove 1/2 inch of the groung wire coating. Then as an afterthought decided to check it for current to be sure it had no voltage, after reconnecting battery.
I then tested the orange wire and got only 6v and 5v on the tan wire.
Is that normal?
Thanks in advance.
Trace the O2 sensor wiring harness from the connector up to the top of the engine and make sure it hasn’t gotten melted somewhere.
Sorry forgot to include this in my last post.
Wire colors for vehicle side fuel pump connector are pink w/blue stripe, tan and dark green, (not black). Were some 90 models different colors?
I don’t think so. I’ve been referring to the connector on the component, not the vehicle harness.
Sorry for any confusion.
The post made by John Springer(May 21 2016), he was confused as to which fuel pump harness the extra ground needed attached.
You had replied that it was the part that belonged to the vehicle, not the fuel pump.
My post may 14th I was referring to the fuel pump not the o2 sensor.
My o2 sensor had checked out 5v on the orange sensor wire.
As far as the voltages (6 and 5) on my fuel pump harness the vehicle should be running for that test.
The written word sure is open to all kinds of confusion.
I realy appreciate your time you spend on the forums and here. I will be making you a donation soon for all your help as you dont have to deal with any of it. I am sure it goes unapreciated by most people and I hate being like most people.
Thanks Cruiser.
90 XJ stalls when it’s warm. Temp gauge rises high when this happens. On the road one day and completely shut down, no power. Had a burnt wire at the starter relay which was the FUEL pump wire. Went to start and then I turned off ignition and pulled out the key, the Jeep was still trying to turn over when the key was out!. Had to pull ground at the battery to make everything stop and that’s when I noticed burnt wire at starter relay. Replaced the pump eventually. Didn’t find a grounding issue anywhere in that area from relay to fuel pump. Week later Jeep stalls again… Just stalls. Everything else worked. Took me 20 minutes to go 5 blocks home. Start then stall…start then stall. Replaced so many parts on the Jeep over the months. Mind boggling.Totally stumped. Any other thoughts? Possible short in ignition? IAC issue? Changed the CPS. Changed TPS. Changed O2 sensor. New fuel pump. Fuel filter. New spark plugs. New distributor. New starter. New starter relay. New injectors.
New parts are not always good quality, especially Airtex fuel pumps. Test your fuel pressure and do the fuel pump ground upgrade.
Hi there
My Mj has had problems with the fuel gauge( it read half tank when in reality it’s almost empty. Not a big issue since every time it’s getting closee to 1/2 tank I just refilled it.
I did the ground improvement today and now the fuel needle went beyond full and I’m sure it’s not.
Any toughts on this gauge reaction?
Thanks in advance
How far past full? I’d run it for a while and see how the gauge reacts.
My fuel gauge had the exact problem. I bought a cheapo sender assembly and it fixed it. The problem was with the old fuel level sender, it probably wore out. If I could do it again, I’d swap the bosch fuel pump into the sender before installing it, who knows how long the crappy chinese one will last. At least on these Renix jeeps you don’t have to drop the tank to get the sender out.
Cruiser,
I’m having an issue with my 1990 jeep reading completely E on the gauge, but only have used around 11-12 gallons when I fill up. I know the XJ has a 20 gallon tank, so something isn’t adding up here. Any ideas on what that issue could be?
The sending unit could be faulty. Have you upgraded the ground though?
Hi, I am having trouble with my fuel pump. I just got this jeep not to long ago and replaced the pump, filter and relay. The pump is not sending fuel to the engine. I’ve replaced all sensors, except the coolant temp, oil pressure and I think that’s about it. I’ve checked voltage at the pump and it’s 6.5, I’ve checked at the resistor and it’s the same then I checked at the relay and it’s 12v. Any idea what it could be?
bypass the resistor on the passenger side inner fender first.
I justwent thru the week of hell with my fuel pump. At one point I get this much larger external high pressure fuel pump made by Bosch and was going to put it in line with the pressure side of the old pump. NG won’t work because you can’t draw thru these pumps but low and behold you can actually put it on the in tank assembly! it is twicethe size of the old pump bot you can hold it on with a couple of large hose clamps. Be sure to get the pump with hose barbs commong out of the pump.
Now I need to replace the gas tank! The insides of the old tank are toast. I hope the old tank comes off OK.