fuel needle not working

Hi,
The fuel needle is not working and the light is always on.
What can this be.
It´s a 1992 bmw 316i with 138.000 km.

Thanks

When this happened to my car, it was the fuel pump under the rear seat. My other symptom was that the car would "run out of fuel" when I had half a tankful left. This was because the pump wasn't pumping from one side of the tank to the other.
The pump cost £115, and it only took 30 mins to fit.

When this happened to my car, it was the fuel pump under the rear seat. My other symptom was that the car would "run out of fuel" when I had half a tankful left. This was because the pump wasn't pumping from one side of the tank to the other.
The pump cost £115, and it only took 30 mins to fit.


Thanks
Pedro Prosperi