Fuel Gauge reading in reverse

Just installed a 1994 XJ motor,trans and front end into my 1990 MJ 2wd Eliminator. It's now 4X4 . Changed the wiring harness,dash and computers. Everything works great except the fuel gauge. When the tank is full it reads empty and when it's empty it reads full. Anyone know why this would happen??

Thanks

Roy

Yep...

After 91 they reversed the polarity on the fuel gauge. You are using the old sender, and a new gauge. You need to swith one or the other.

Yep...

 

After 91 they reversed the polarity on the fuel gauge. You are using the old sender, and a new gauge. You need to swith one or the other.

yep opposite problem here we put a nonmolested tank from a parts 93 jeep in the xj and the thing reads backwards doh! :roll:

we just laugh when the E light comes on to let us know its full :brows:

Yep...

 

After 91 they reversed the polarity on the fuel gauge. You are using the old sender, and a new gauge. You need to swith one or the other.

This is true. Prolly be easier to swap out the fuel gauge from your old cluster than pulling the sender out of the tank and changing it. Pretty sure the gauges are interchangible unless your old cluster was the one with the idiot lights and the HUGE fuel gauge.

My 91 reads like this also. makes for finding mileage a lot easier. Since the light normally comes on with two gals left, I can now figure that mileage i got in those two gals once it goes off.

Alex

My 91 reads like this also. makes for finding mileage a lot easier. Since the light normally comes on with two gals left, I can now figure that mileage i got in those two gals once it goes off.

 

Alex

Errr Alex, why is your 91 fuel gauge reading in reverse? Thought your rig was a 91 w. no mods??

Errr Alex, why is your 91 fuel gauge reading in reverse? Thought your rig was a 91 w. no mods??

Now where would be the fun in a rig with no mods? lol

Nah, it is like 3 trucks in one (a red one, a smurf truck, and a white one) plus some XJ parts. It has a new Jasper motor with like 16k miles, XJ Waggy lighted mirror visors, XJ Waggy OHC temp/comp, XJ Waggy control center display, CAD "fix", 3" lift...

The doors are both from an older truck which uses the old AMC keys (each door diff too, only had drivers side key) rather then the one key setup like the 91 should have for doors/ign/glovebox. I put an old 86 chrome 10 slot grille on the stock 91 header panel (that was a pain).

So, as you can see, not all that mod-free now is it? But to throw this out there, I'm sure the fuel pump might have gone out and just been replaced with an older one maybe before I got it? Who knows.

Alex

Yeah, knew you had plenty of mods, but didn't know a PO swapped out the pump/sender with the reverse polarity older sender. Not too smart........ :nuts:

Yeah, knew you had plenty of mods, but didn't know a PO swapped out the pump/sender with the reverse polarity older sender. Not too smart........ :nuts:

Talk to rob about that one. One of these days I am going to fix it, but I am so use to it I don't notice it anymore, just freaks out people who ride with me and I just filled it up before I picked em up. They are always waiting on it to die at any moment. I think fixing my missing floor is top on my list right now though. lol

Alex

Thanks for the help guys. Fuel pump and sending unit gets changed this weekend.