In an internal combustion engine, fuel starvation is the failure of the fuel system to supply sufficient fuel to allow the engine to run properly, for example due to blockage, vapor lock, contamination by water, malfunction of the fuel pump or incorrect operation, leading to loss of power or engine stoppage. There is still fuel in the tank(s), but it is unable to get to the engine(s) in sufficient quantity. By contrast, fuel exhaustion (also called fuel depletion) is an occurrence in which the vehicle in question becomes completely devoid of usable fuel, with results similar to those of fuel starvation.
All engine-powered modes of transport can be affected by fuel starvation, although the problem is most serious for aircraft in flight. Ships are affected to the extent that without propulsion they cannot maneuver to avoid collisions or beaching. On aircraft, fuel starvation is often the result of incorrect fuel management, for example by selecting to feed the engine from an empty tank while fuel is present in another one.
