Why does the fuel gauge show less than full after refueling?
2 Answers
Why does the fuel gauge show less than full after refueling? The reason is that the fuel gauge float is damaged. The following is an introduction to how to check the car fuel gauge and the principle of the fuel gauge: How to check the car fuel gauge: Generally, there are two English letters on the fuel gauge, E stands for empty, and F stands for full. There are two coils inside the fuel gauge, located on the F and E sides respectively. The sensor is a variable resistor controlled by the float height. The change in resistance determines the strength of the magnetic field of the two coils, which in turn determines the deflection direction of the pointer. How the fuel gauge works: There is a float in the car 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, and the corresponding displayed value is the remaining fuel in the tank.
I've been repairing cars for over 20 years and often encounter situations where the fuel gauge doesn't show full after refueling. The most common issue is with the fuel tank float - that small device floating on gasoline might get stuck or be clogged by sludge, preventing it from rising properly. There was an old Buick where the float arm got rusted and stuck halfway, showing only three-quarters full after refueling. Another possibility is loose or corroded wiring connections to the sensor, causing signal transmission abnormalities. Some cars also have inherent fuel gauge calibration deviations - I've seen BMW models where the needle slowly rises to full after driving a few kilometers post-refueling. If you've recently replaced the dashboard, it might require reprogramming. I recommend not ignoring this issue, as an inaccurate fuel gauge can easily lead to misjudging remaining range, which could result in being stranded on the road.
