Fuel and speedometer problem

[kook911]

Back story, I have a 87 MJ with a 91 xj drivetrain and engine. 4.0 and ax15.   I swapped out the complete engine wire harness and mated it with the MJ rear harness. I follow the write up on what to connect which wires to. Now onto the two problems. 

 

First one one is with the gas gauge. It is reading correct but backwards, empty is full and full is empty. Did I by chance hook up a wrong wire backwards?  Really don’t know where to start looking but would like to get it corrected. 

 

Second problem my Speedo and mile trip meter doesn’t work. The rest of the gauges read correct and work. So far I have taken off the speed sensor and tested it  on the multi meter. When I spin the sensor with the multi meter hooked up the sensor beeps every rotation. I also disconnected the wire harness inside the engine bay and clean the connectors out with contact cleaner.  I also have taken the gauges completely out and made sure all the screws were tight on the back of the gauge. My only thought is the sensor is giving me a false positive. Any other ideals?  

 

 

[HOrnbrod]

Fuel gauge:  The potentiometer polarity of your original Renix fuel sender is opposite that of your 91 fuel gauge, thus it reads backwards. The fix is either find an MJ HO fuel sending unit and swap it in (lots of luck finding one), or pull your Renix sender and swap the two wires on the potentiometer by soldering which will change the output polarity to the gauge. I bench tested this a while back and it works, however the Renix and HO potentiometers are of different values, so the gauge won't be very accurate, but will indicate properly. Best advice - live with it.

 

For the speedo, what instrument cluster are you using? An HO cluster? The 91 used a one-off 2-wire VSS sensor.

 

 

[kook911]

Well thanks for the fuel gauge. I will just live with it. Rather it be accurate then read correct and wrong way. 

 

Speedo I am using the HO cluster. I want to say it's a two wire but not sure. I will check when I get home. 

[carnuck]

Well thanks for the fuel gauge. I will just live with it. Rather it be accurate then read correct and wrong way. 
 
Speedo I am using the HO cluster. I want to say it's a two wire but not sure. I will check when I get home. 

‘91+ are Electronic speedo and if you used the same transmission you don’t have the sensor it needs but I have installed a ‘91 Wrangler (only one stock from the factory) sensor which has a pass through for speedo cable and EFI speed sensor.


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[kook911]

I used the ax15 mated with the np231j. So the drivetrain has the electric speedo. The speed sensor I’m talking about is on the tail shaft of the transfer case. 

[carnuck]

I used the ax15 mated with the np231j. So the drivetrain has the electric speedo. The speed sensor I’m talking about is on the tail shaft of the transfer case. 

Same as I’m talking about too.

Napa part# ECH VSS110








Dodge used them in some others too.




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