Fuel gauge says empty but tank full

The fuel level sending unit is integrated in the fuel pump, which is located in the tank. The age of your vehicle warrants replacement of the fuel pump as a unit. Never try to repair a sending unit Just make sure the float for the sending unit is free to swing when installing the fuel pump into the tank. Also empty water out of fuel pump well of the fuel tank

Float arm is stuck. Take out fuel pump and see what float arm is catching on and or replace fuel pump altogether

the fuel level sender is inside the fuel tank, part of the fuel pump assembly. did you or was the tank replaced before??they may have bent the float arm on reassembly . you can buy the sender from your parts supply store .you will have to drop the tank to do this it clips onto the side of the pump assembly. run it almost dry first as the tank is big n very heavy even 1/4 full. you can try to bend the old arm

but its very hard on the "sender" as for level indicator full to empty, think of the shape of the tank narrow at top to widest point in the middle (full to half) wide middle to narrow bottom( half to empty)

its just an overall volume thing

It has to be the float, may need recalabrated

The problem is in the fuel sender unit in the tank. It sounds like the float part of the sender unit is binding when it's at the top (when tank is full) and hangs up there till it falls back down when tank is near empty. It will likely have to come out to be checked, fixed, or replaced. Good luck.

Sounds like the sending unit is bad n the tank.

That definitely sounds wierd, sounds like the wires are backwards on the float assy.

in side the tank on the side of the pump there is what thy call a sender not to be confused with the sending unit. The sender is atached to the float and tells the gauge how much fuel you have.

sounds like the float isnt sitting proplery in the tank

You don;t say whether the fuel gauge is reading accurately, or whether it's always on empty. If the gauge is always showing empty, it's most likely a problem with the sending unit in the fuel tank. Check the resistance across the two terminals of the sending unit.

On a C900, the fuel sender level unit is separate from the fuel pump and located on the right side top of the tank, accessible by removing the trunk floor lift up panel (the pump is located on the left side top of the tank.
Possible problems are: electrical line off or broken, float not working (it's fairly delicate); or gauge not working.

Test the resistance of the sending unit with the lines disconnected, the resistance should be 2.6 to 3.8 ohms full tank, 63.3 to 67.5 ohms empty tank; and test for voltage across the top of the sender unit, if no voltage, that's likely the problem!

If the gauge is otherwise reading accurately (showing 'full' for a full tank, etc) then the problem is likely a gauge malfunction and can be simply replaced.

Good luck!

Saabreur