Fuel Gauge Problem

[Phandy]

Hi, it has been a while. My 2003, 1.8 V40 has developed an intermittent fuel gauge problem.

The gauge is faulty and will say the tank is empty after I have just filled it up, or it will say I have 110 miles in the tank and 5 miles later it will claim I only have 15 miles left.

The problem started after I changed the fuel filter. I changed the filter as the car was stuttering and stalled for the first time ever a few weeks ago.

I have read a few guides and it seems the problem is probably on the sender unit under the back seats. Since the gauge has not just stopped working, I am guessing it's a ground / contact issue somewhere around the unit.

Has anyone got any tips? Would it be easier to just buy a second hand pump? it looks like the sender unit is part of the pump and not something you can pop out.

Also, around the fuel filter there was a plastic bracket with an electrical wire attached to it that seemed to connect to something above the fuel tank. Does anyone know what the wire does?