A is a frequently (but not always) essential component on a car or other internal combustion engined device. Many engines (older motorcycle engines in particular) do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank or under high pressure to the fuel injection system.
In tank fuel pumps fail mainly due to age or mileage. The main culprit is the tone ring or commutator where the brushes make contact. Quite often you can catch that by looking at the wave form on a scope. You will see an uneven wave pattern with one or two more spikes.
In rare cases the introduction of water in the tank can potentially damage the pump.
If you have a diesel engine , pouring gasoline in the tank by mistake can kill a fuel pump in no time. Pouring diesel into a gasoline engine on the other hand doesn’t cause much damage other than the vehicle will eventually stall .
Purely mechanical failures are rare. The gas passes through a fine mesh before getting sucked into the pump.