1993 Jeep Wrangler Inaccurate fuel gauge and speedometer

Tiny
AGENT
  • MEMBER
  • 1993 JEEP WRANGLER
Electrical problem
1993 Jeep Wrangler Four Wheel Drive Manual 113000 miles

Hi there, I have recently bought this Jeep. The fuel gauge on it is not accurate -- it stays in one place about quarter tank mark and doesnt move. Also the speedo meter is not accurate -- eg if you are doing 60 miles per hour it will show 35.

Thanks for your help in advance
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Wednesday, April 30th, 2008 AT 7:32 AM

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Tiny
AIRSOFTSOLDRECN9
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Well these two are easy to diagnose but maybe not so much fun to work on. The speedometer is electrically operated with a control wire running from the spedometer sensor in the rear of the transmission to the speedometer on the car. Now running larger tires can knock this off anywhere from 5-15mph just to let you know so if you have anything bigger than 33'' you might want to consider that an issue. Now the control wire that runs creates a variable resistor and each specific resistance corresponds to a change in the meter. What that ratio is I have no idea but more than likely the speedometer guage is at fault. Now for the fuel guage my guess if it is holding steady no matter what probably the sending unit is faulty. Unfortunatly this is in the tank and the tank has to be dropped to access it. The sending unit is also permanently attached to the pump so to get a new sending unit requires a new pump ($100-125). The guage is a possibility and it is easier to start with since all you have to do is replace the panel. You could also try testing the guage with a voltmeter. Gently change the dial by hand with your finger and see what happens with the resistance. I think 95 and younger vehicles use 0-80ohms (empty-full) but then jeep decided to switch it and make 100-20 ohms after that year. I am not sure but the point is to get a reading at all. You can try checking this with different amounts of fuel in the tank too. The leads though are not very obvious so a wiring schematic may help some. This should get you started.
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Tuesday, May 6th, 2008 AT 12:00 AM

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