eaglescout526

Lets see, where to begin. I spent a few hours collectively trying to figure out my fuel gauge issue. Same issue with another gauge, same issue with a later cluster but a little less sensitive. I added a ground thinking that was part of the issue and it wasnt. So I am now looking at the sender being an issue which will be incredibly odd but I shall see. Luckily I have a couple sending units to goof with and I plugged it in place of the one in the tank, recreated the sloshing effect and didnt have the issue on the gauge. I worry that I may end up wasting my time on chasing this bizarre issue. I even tested the current sending unit outside of the tank but I didnt account for any sloshing or anything like that so it could be busted in a weird way. Just 84/Renix things. Still have some stuff to do like the wiper bushings, oil change, cruise and AC. Gonna try that free zone stuff I acquired a while back. I also got this done: Whats different? Well I made some custom brackets to get it in place. Thanks to some examples of this radio for the XJ on ebay, I was able to copy the brackets to a degree and get this radio in place correctly. Im pretty proud of the few hours I spend cutting and designing the brackets. Now it wont flop around or move with the XJ/MJ specific radio adapter bracket.

It’s not locked right?

An interesting dynamic indeed. Course I don’t think the bronco II was a great name which probably didn’t help to sell it.

Ahhh my XJs direct competitor

If you know someone tossing out a set of washer and dryer, that’s great cheap floor pan metal that’s already treated to fight rust.

Indeed I am! Got all three palms. And then aged out haha.

Surprise it didnt turn into a DeLorean for the time traveling that has happened here haha. Well done finding the post for this MJ.

22?! Ive only owned 5 automobiles.

It should. The vac harness didn’t change from 87-96 with that control deck.

Ok did some more digging. I think I know why there is such an Ωhm difference on harness vs sending unit. Looks like beginning in 86 the cluster became known as "type 2" which has a solid state module for the fuel gauge. Probably thus resulting it working in conjunction with the new FSU vs the old one being just the float and not having a pump. So to probably fix my issue would be to swap to a 86 blue cluster and I shouldnt have any issue with the reading of the fuel level. Now the type 1's have a white housing, blue film to dim the lights and the fuel gauge has a printed paper circuit with resistors on it.

My thought too. When I get that resistor, I hope that solves the problem. While doing what Eagle_SX4 suggested I found something very very interesting. I didnt even actually start it up I just tested the sending unit first. It reads true at 75Ωs right now for an almost full tank. Connect it to the harness and that is instantly cut in half to 40Ωs. Now probing the two wires that B and C on the connector to the chassis side, I read .006VDC I went and added a ground from the fuel filter mount to the SU. No change. Harness side reads 57Ωs. Plug the two together and you have 40Ωs when reading the full tank. So I can only suspect one thing, 84-86 clusters may not be as plug n play as we may think with Renix. Im going to look in the 86 manual of the cluster and see. But that residual voltage is concerning. I should take a pic of the 84-86 style fuel gauge back side.

Uh huh!! and good call! Ill have to be quick on that one. Whats odd is the sending unit is from an 86 2.5L XJW that looks otherwise completely pristine.

Ok here’s a 50second clip of what it does. I backed out of the garage a little, pulled back in and recorded the gauge basically going from full to half a tank and twitching it’s way back. Just for context what it is doing. I have never seen this before.

Once power is off at the ECU it will shut everything down. 86 TBI used the same alt but 87-90 used a different one that has 4 wire plugging into it. One is for the gauge itself, the other is a splice of both battery and to a fusible link. I can see the tan wire providing some sort of back feed but this looks pretty basic with no issue. This is from the 86 electrical manual that has TBI with the above alternator.

Looks like a reman delco remy by ultima Ill try the diode and see what that does. Whats odd is my alt isnt doing exactly what it did to you with your Eagle and keep it running. Oh yeah I know that. I can do the same to my MJ and get the gauge to move. What bothers me is when I say it moves and is bouncy I mean it bounces and moves. Like it will move from where it rests after reading correctly to suddenly its at half tank when you slosh the tank or move like rolling backwards or driving forward. And when driving it will go down pretty damn close to E until you come to a stop and let it level out. This is what bugs me the most aside from the back feeding. It will bounce its way down or back up. Ive never seen a fuel gauge do this unless its the full speedo size matching gauge and even then that didnt move the way this one moves. I can plug another sending unit in and move the arm up and down and see the gauge behave normally with the engine off as thats the only way to really test the gauge functioning.

Like the title says, its getting back fed power. On the 84 XJ. Now its some, like maybe 6 volts at the most but not a full 12. Now I just want some working theories. I have a plan of how to get to the bottom of this and why this is happening. I only noticed this from two things. First, the fuel gauge is bouncy and sensitive. At first I thought the old gauge was bad as the light didnt really come on for low fuel. I swapped the gauge for a NOS one and that worked, light and all. Drove around, got some gas and noticed the float was stuck again. Great. Well its unstuck now and sensitive. And I mean sensitive. Like you can rock the whole XJ and it will start moving. Hell even just backing out with the trans not in gear and letting it roll back on its own and the gauge will start moving. Second, upon trying to figure out why this is, I removed the cluster fuse and found that the brake light was DIMMLY lit along with some of the gauges getting power when it should be dead. Which is how I noticed I am being back fed. Why? Not sure. This is when the engine is running. We all know what I have done to this XJ. TBI swap, System Sentry, dash to chassis ground per cruisers tips. But none of these I can find any correlation at all as to why this is. I could be losing my mind and the alt is back feeding the power to the cluster, but I would see the voltage gauge show some life with maybe 13v from charging. Nothin. ICM could be back feeding power to the tach, but not likely as those are pulses. But it is only about 6volts for the brake light being dimmly lit. I went on a whole rampage and pulled every fuse while leaving the cluster fuse out and the brake light didnt turn off. Is my sending unit back feeding power somehow? I could have two separate issues here for all I know. Just any theories one might come up with while having read this will be awesome. I dont think I will be tackling this today. Probably next weekend or after. Oh and Ω, I did pour over the wiring diagrams to see what it could be. I found nothin that stuck out to me.

5/1/2017 Found this absolute oldie. This is a great example of what happens when it becomes an addiction and an obsession. I wish I could find some of the older stuff from '16.

My two cents, don’t settle unless you are coming up empty on your search. Granted it does take time. I say this because 86 has the 2.8L which sucks but if you have time and money, you can search and swap to a 3.4L from a GM car and get better power and reliability 86 early 87 had a Renault 2.1L turbo diesel. If you’re new to Jeeps and this history, steer clear of this engine as you’ll have a hard time finding parts. If not, pick one of these up if you can find it. Renix is really easy to work it for 86-90. All you really need is electrical knowledge and a multimeter to diagnose damn near everything on these Jeeps. 91-92 HO is a different animal. It’s Chryslers OBD1 and provides better diagnostics but from what I have heard, sensors are becoming hard to find like some of the Renix specific ones. All in all, a damn good daily driver, a unique one too. If taken care of, it will take care of you and provide a long life of worry free and comfort. Reliable is an understatement for the engines and trans options. If you’re not careful, you might find yourself with an XJ or an SJ haha.

So lets see. AC as it turns out, has had a slight leak for probably since the time I owned it as there was oil on the underside of one of the caps and now the valve has failed resulting it being stuck open. So theres that, not the expansion valve like I thought. Oh well I will charge it with some freezone that I have as a 30lb keg laying around. I fixed the heater control valve. That was stuck and I dont know why. But all I know is that i was annoyed to be driving and not have cool air while the temps outside are cool. I have to figure out why cruise control isnt working Have to replace the wiper bushings And the float is stuck on the sending unit again....its got a full tank so I have to wait or hope it frees itself. All in all, a blast to drive still!

At the moment no but it’s hanging in my garage as decor haha.

Oh damn yes!! I forgot about the color matching. If you’re good at masking, it can be done. I did it on my MJ to match the charcoal. But I do have a honey one and it’s pretty neat. Had a NOS Baltic blue at one point.

................Hmmm. This is a new one. If I had to suspect, you need the LED specific flasher to get them to work together. Thats my guess. I was gonna say the sockets are bad but you said they work with the lights off.

Love it! Would’ve been too much work, effort, time and money to convert for it to be “easier” for them to work on.

No that doesn’t have to be removed. I think the rear splash guard instructions are in my signature. If not I’ll snap a pic when I get home. Nope it’s not. I’ll snap a pic when I get home.

That’s farmland Waddell. didn’t even know there was one out there.