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New to me MJ have some questions


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Hi Guys.  I'm new to the forum but have been reading a ton of great info on this site since I bought my comanche about 6 months ago.  I have a couple questions and wanted to see if anyone could help me out.  The MJ is a 87 2.5L 2wd short bed that the previous owner swapped in a 93 4.0HO and converted to 4wd.  Everything works except for a couple things and for the life of me and can't figure out or find info on.  Any help or direction you guys can point me in would be great.  Thanks in advance!

 

-Radio comes on when the headlights are turned on (no key in ignition)

-No power to "dome lights".  Can't figure out where the wiring would go without tearing the interior out.

-Fuel gauge reads backwards.  I've read it all but the info seems scattered.  I know the polarity changed in 91? so that is why it reads backwards.  I'm not sure if the pump has been upgraded but truck drives good so I'm assuming it has.  I'll pull it to be sure soon.  What is the easiest way to get the gauge accurate and in the right direction?  I was thinking of doing the autozone pump assembly and swapping in a bosh pump if I don't have a tray in the tank.

 

 

Thanks!

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I'm guessing it has an XJ wiring harness in it, since you believe it's a 93 HO engine.

 

Radio...  Probably tapped the wrong wire for the 'switched ignition' to turn it on.  I think you'll have to pull the dash and chase what it's hooked to.  Radio/stereo installs tend to be the #1 hacked thing in vehicles since every person out there takes a stab at installing one.

 

Dome lights? I assume you mean the ones in the B pillar.  If so, I'm guessing because it has an XJ harness in it, there wouldn't be anything to hook them too without splicing or swapping some plugs and extending things.  Unfortunately you'll probably have to pull the entire interior to find out what they did and make it right.

 

For your fuel gauge sender issue, the easiest would be to try to find a HO sender/pump/pickup assembly from the classifieds here, eBay or a junkyard.  They aren't easy to find.  Hacking the tray to fit an XJ sender is well, hack, but if need be that would be the next option.  Or I suppose you could order a new tank that doesn't have the tray/baffle in it, but I'm not sure which comes without, and honestly it was in there from the factory for a good reason.

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Before pulling the interior apart;

The b-pillar lights tend to be problematic, with poor contacts that quit working over time anyhow. Not working doesn't necessarily mean they aren't getting power, so I would check that first. Should be three wires, one ground, one constant hot and one switched 12v with the doors. There are also optional footwell lights that attach to the bottom dash panel (the long one that goes all the way across with the ashtray in it) that are on the "dome" circuit and should also be getting power with the door switch.

The radio, even if the factory unit, could've been pulled for an aftermarket unit then this one was put back in when a PO sold it, so it's most likely hooked up wrong directly behind the radio. Pulling the radio out is much easier than pulling the whole dash. There's a couple threads on here about stereo wiring, but I found that my factory units had a diagram specifying which functions on the plug did what, and it should just be a case of matching those functions to what's on the wire harness. My money's also on the ignition switch and dash light wires getting reversed in there.

I seem to recall the "dome" circuit at the fuse panel doesn't actually have much to do with the dome lights, but I might be thinking about a different vehicle. 

 

But those things are both assuming the PO knew what they were doing when they did the 4.0 swap, and if things don't check out, you may end up having to pull it all apart just to be sure it's all done properly.

 

As to the fuel gauge, as was said the Renix gauges and the HO gauges are reversed polarity through the sending unit, so HO gauges will read backwards with a Renix sender and vice-versa. While you've got the dash bezel off to check out the radio, see what colour the back of the gauge cluster is, which will give you a clue as to what it came out of and how to fix the reading backwards issue. With the exception of the fuel gauge and also mechanical vs electric speedometer, I'm told the Renix clusters will work with an HO, so it's uncertain what sender you have. I can imagine someone leaving in the mechanical speedometer just cause it's easier to deal with.

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