E30 Zone

Guys, i have a 2 door 323i and my fuel gauge won't rise to the 55l marking when i fill up the whole tank. At first, i tot it could be the problem with the fuel float, replaced with a good unit. Yet, it stays the same. Tested the fuel gauge and it manage to reach the 55l marking when tested with a device (not sure what it is). However, it did manage to go to the bottom and the fuel tank indicator light would lite.

What could be the problem? My mech ran out of clues. Next i would try is to fill up the tank and remove the speedo and manually adjust the fuel gauge needle. It is ok to do so?

pls advice. TQ

possibly the wrong clocks in the car, i fitted a 318i instrument cluster into a 316(carb) and it never went up properly and always readed low but it was fine in the old car.

iirc it could be to do with the size of the fuel tank

i think the size of the fuel tank is accurate. I had filled up to 50l at a point of a time. Could be the gauge problem as the speedo had been replaced with a used unit. thx for the input.