Fuel guage

[fireman181]

I am having problems with a fuel guage reading empty. The tank is kept full,diesel, I have tried to remove the sender unit getting most of it out of the tank, but not the arm. The arm did move freely. Read somewhere that the float could be "water logged" and opinions.......the unit is an VRO

[mdbee]

If you have checked the meter by grounding the sender wire and it does work, replace the sender unit.

[fireman181]

By grounding the meter due you mean disconnect the sending unit and ground that wire??

[CarelessNavigator]

The sending unit usually uses a float connected to a variable resistor. When the tank is full, the resistor is set to its low resistance value. As the tank empties, the float drops and the slides a moving contact along the resistor, increasing its resistance, finally reaching its highest value when the tank is empty. In addition, when the resistance is at a certain point, it will also turn on a "low fuel" light on some vehicles.

Meanwhile, the indicator unit (usually mounted on the instrument panel) is measuring and displaying the amount of electrical current flowing through the sending unit. When the tank level is high and maximum current is flowing, the needle points to "F" indicating a full tank. When the tank is empty and the least current is flowing, the needle points to "E" indicating an empty tank.

The system is fail safe; a fault that opens the electrical circuit causes the indicator to show the tank as being empty (which will provoke the driver to refill the tank) rather than full (which would allow the driver to run out of fuel with no prior notification).

I got that from wikipedia by typing fuel gauge hopefully that helps you to understand it a bit better.

[sailingdog]

If the float was a hollow float and has been punctured, the sender will often read empty or close to it regardless of how much fuel is in the tank. You might want to see if the arm moves as the fuel level changes. If it doesn't then the float is probably shot.