If your vehicle is showing fuel gauge needle bounces around erratically while driving, here are the most likely causes and the parts you'll need to fix each one.
The electrical contacts on the fuel sending unit inside the tank wear out over time. As fuel sloshes while driving, the worn contacts cause the resistance signal to drop out or jump, making the gauge bounce.
A loose ground wire or corroded electrical connector at the fuel tank can cause intermittent signal loss. Vibrations from driving make the connection cut in and out, resulting in an erratic needle.
If the fuel pump was recently replaced, the float arm may have been bent during installation, or the wiring connector wasn't fully seated. This can cause the float to bind or the signal to fluctuate.
The tiny stepper motor that physically moves the needle on the dashboard gauge can fail or develop bad solder joints on the circuit board. This causes the needle to twitch or bounce independently of the actual fuel level.
Internal baffles inside the fuel tank are designed to prevent fuel from sloshing violently. If a baffle breaks loose, fuel sloshes heavily during driving, causing the float to bounce rapidly.