Spark-ignition engine system supplied with gas and apparatus comprising such a system, such as a motorised pump or an electricity generator

The invention relates to an autonomous gas-powered internal combustion engine system (100). According to the invention, the engine system comprises an internal combustion engine (120) equipped with a combustion chamber (11); a gas bottle (20) and a regulator (21) which supplies gas at a pressure P1 as well as a connection interface (150) between the regulator (21) and the combustion chamber (11) of the engine, this interface comprising an injection device (10) equipped with a pressure adjustment means (103) for maintaining the pressure at P1; a connection pipe (30) for connecting the regulator (21) to the injection device (10) and a connection pipe (31) for connecting the injection device (10) to the combustion chamber (11), said pipe (31) being suitable for expanding the gas from pressure P1 to a pressure P2 required at the inlet of the combustion chamber (11) of the engine via a throttle screw (104).