Liquefied gas feeding system for an internal combustion engine with detector of the minimum level of liquefied gas

The system has a gas supply line (12) for supplying a gas from a liquefied gas source (10) to a combustion engine. A detection device (16) comprising a positive temperature coefficient (PTC) sensor, is arranged in the supply line between the source and the engine. The sensor detects the occurrence of change of liquefied gas from a liquid phase to a gaseous phase in the supply line.