Device for regulating the flow of fuel injected into an internal combustion engine. A rolling diaphragm is exposed on one side to the pressure prevailing in the induction pipe of the engine and on the other side to a pressure in the neighbourhood of atmospheric pressure by way of a conduit in which a valve device is inserted for normally closing the conduit. The valve device is shifted to the conduit opening position when a cam regulating the amount of fuel injected reaches the vicinity of an extreme position corresponding to predetermined conditions of engine operation.