The fuel sending unit has a float arm that sits in the liquid gas. When that arm moves up and down, it changes the resistance to ground on a variable resistor. That resistance is then translated and sent through the cars wiring and electronics to determine where the needle or digital gauge is positioned.

How do I test a fuel gauge sending unit?

0:022:20How To Test A Fuel Level Sending Unit - YouTubeYouTubeStart of suggested clipEnd of suggested clipPosition it will be in the tank. Most often theyll be mounted upright with the float moving up andMorePosition it will be in the tank. Most often theyll be mounted upright with the float moving up and down the level of gasoline. If you test it sideways.

How does the fuel gauge work?

Fuel gauges work by measuring the voltage across a variable resistor within the sensing system, to determine the level of fuel; which is then relayed to the driver via the indicating system.

What happens when a fuel sending unit goes bad?

A faulty fuel gauge sender may cause the gauge to suddenly change positions, or give an inaccurate reading. The gauge may appear to be at three quarters, and then only a few minutes later will change to half full, or vice versa the gauge may appear to be full, only to have the gauge climb higher a short while later.

How do I fix my fuel gauge sending unit?

1:202:58How to Fix a Gas Gauge (Sending Unit Replacement)YouTube

What would cause fuel gauge to not work?

What Causes The Fuel Gauge Not To Work? An inaccurate fuel tank reading is most commonly caused by the sending system which reads the fuel tank level and sends the reading to the gauge. Issues can also stem from a bad gauge, blown fuses, or corroded wiring. You can self-test all of these parts at home with a few tools.