Whenever I start my Jeep up the fuel guage goes all the way to "full". When I cut the Jeep off it goes back to "empty". Is there any way I can check to see if it is the guage or the sending unit?

Thanks,

From what I've read on my 90 thats whats suppose to happen. No power to the guage it should read E. When power to it should read what is in the level of the tank. If you disconnect the sending unit harness at the tank and turn the key on it should read F. The guage is simply an ohm meter and reads resistance between two grounds. The ground coming the tank is dependent on the level of fuel. At empty there should be no resistance. At full it should be 88 ohms.

What you can do is pull the cluster and measure the resistance between the 3 and 4 pins on the harness. No. 3 is the ground for all the gauges. No. 4 is the ground coming back from the fuel sending unit. If the reading is above 88, your sending unit is had. I would try checking this when you're sure you're around half a tank. This is what my manual says for a 90. I'm not sure if its the same for a 91.

My guage reads half a tank when empty and, 3/4 whens at half a tank, and full between 3/4's and full.