The most common cause of pump failure is operator negligence in not changing the fuel filter every year. The fuel filters get plugged up due to the ethanol in gasoline causing filter material to crumble and plug up the filter. The pump cannot pump anything and burns up. The other cause of pump failure is the brushes wear down after many rotations or hours of use. The brushes no longer make contact with the commutator to send electricity to power the rotor and the pump motor stops turning. Sometimes bumping the fuel tank may cause the brushes to make contact and briefly power up the motor.