What is the reason why the fuel gauge of BMW 525 does not rise after being filled up for a long time?

[LaLawson]

It may be caused by the oil float sticking, aging, or damage leading to oil ingress. In this case, the oil float cannot float on the gasoline, but instead suspends in the gasoline or sinks to the bottom, resulting in inaccurate measurement or no response. The solution is to remove the fuel pump for inspection. Here is some extended information: 1. How the fuel gauge works: There is a float (oil float) in the car's fuel tank, which drives a sliding resistor. As the fuel level in the tank changes, the potential at the measuring terminal also changes. The car instrument processes this signal and displays it, with the corresponding display value being the remaining fuel in the tank. 2. Other symptoms of fuel gauge failure: The fuel gauge indicates higher or lower than actual; unstable fuel gauge display during driving, with fluctuations up and down; the fuel gauge indicator remains completely still.