A fuel injector for carrying out this method delivers the liquid fuel in measured quantities through a pipe to chambers which communicate through a passage but are otherwise separated by a lift-valve. This valve is raised from its seat by a projection on a needle-valve, and is provided with a port for the passage of compressed air which is admitted through an orifice communicating with the compressed air receiver.
The needle-valve is raised from its seat by the cam-levers and the charge of fuel from the chamber is injected by the action of the compressed air. The continued motion of the needle-valve then raises the lift-valve and the remaining fuel is carried into the cylinder. The needle-valve has a piston guide and its stroke is adjusted by suitably regulating the position of the rod operating the needle-valve lever, relatively to the link operated by the cam, and when the lift of the needle-valve is suitably reduced it fails to open the lift- valve.