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 not delivered to the engine(s) in sufficient quantity. By contrast, fuel exhaustion is an occurrence in which the vehicle in question becomes completely devoid of usable fuel, with results similar to those of fuel starvation.