Improving the fuel pump ground

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.1-fuel pump ground MJ

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.1-fuel pump ground mj-002Solder the connection. Tape it up and reinstall the split loom covering.1-fuel pump ground mj-003

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.1-fuel pump ground mj-004

Revised 10-16-2018



54 thoughts on “Improving the fuel pump ground”

  1. 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.

    1. 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.

  2. 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 🙂

      1. 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.

          1. 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.

  3. 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.

    1. 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.

      1. 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.

        1. 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.

  4. 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.

  5. 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.

  6. 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?

  7. 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!

  8. 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.

  9. 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.

    1. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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?

  14. 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.

  15. 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.

  16. 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

    1. 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.

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