Fuel sending unit question

[jeep690]

So, I'm swapping all my internals from my 89 renix Comanche to the 93 HO Cherokee. Will I need to swap out the old renix fuel sending unit for the Cherokees sending unit or what? How does this work?

[HOrnbrod]

The Comanche MJ fuel sending units will not work in a Cherokee XJ fuel tank or vice-versa. They are constructed differently; mirror images of each other.  Also the polarity of sender's output signal wire to the fuel gauge will be opposite; the change year was 1991. So if you are swapping the MJ Renix dash to the 93 XJ, you will need to use a 1990 or below XJ sending unit in the 93 XJ fuel tank so your fuel gauge will read correctly.

[87Warrior]

Awhile back there was an interesting post to the Comanche Lover's Facebook page regarding a fuel tank and sending unit swap. The post suggests you can use a XJ sending unit assembly in a replacement fuel tank WITHOUT the slosh pan. Even though the XJ sending unit wouldn't be quite long enough to reach the bottom of the tank leaving a few unused gallons of fuel, it seems like a solid idea. I would personally worry about the pump running dry without the slosh pan, but a couple Walbro pickups placed in the tank would fix that.

 

Finally received my new fuel tank and fuel sending unit assembly for my 1988 Comanche. I purchased these parts on Amazon, tank JP5A and a fuel sending unit SP7091H.

I had a bad issue with rust inside the tank and covering the original fuel sending unit so bad that I had to replace them both. The Comanche fuel sending unit is no longer produced anywhere and is very hard to find. So I did some research and found that a Cherokee fuel sending unit will work in the Renault Diesel Comanche fuel tank. The Diesel fuel tank does not have the "pan" in the bottom. The Cherokee unit is a reverse of the Comanche unit so if you were to try and install the Cherokee unit in a regular gasoline tank with the "pan", it would simply not fit. The pickup screen and level arm would hit the pan. Hope this helps anyone who is having fuel tank rust issues.

 

And it is working for one of our own:

I put an xj sender in my Comanche. I think it was for an '88. (Important so the gage reads correctly iirc.). I re- bent it just a bit so it would reach the bottom. I have an 86 long box with the bigger tank, and no pan in the tank because it was a carbed 2.8l. Works great so far...

[buckwheat]

I have done the same basic thing that 87warrior posted. I modified it a little bit, but the main idea is the same. No slosh pan in the tank and a cherokee sender. Has been working well for over a year now. And this is with an 87, so it is MPFI.