I was wondering what could be causing my fuel gauge to not read correctly. It is the stock tank and according to the user manual it should hold around 17 gallons every time i fill up a little above empty it is consistently 11 gallons also when i first got it it would go down and only be 7 gallons is the sensor or whatever messed up im not familiar with how these work i would just like to have a reliable gauge.

 

The sending unit in the gas tank can go bad and give a false reading, or go bad and just stop working all together. I had this happen on my 86 4Runner and my gas gauge would read all over the place no matter how much gas was in the tank, and when i went to replace the sending unit i found that the baffle pan in the tank had broken loose and i had to replace the whole gas tank, but i got real lucky because my cousins neighbor was parting out an 87 4Runner and he gave me the gas tank and sending unit for free, so that saved me a bunch of money.

 

I have had 2 of these go funny. What it was in both of my cases was the ground wire that is riveted to the sending unit. This causes the resistance to change which in-turn causes the gauge to read funny.