PURPOSE: To permit the supply of a required liquid to incoming fuel oil by means of the negative pressure of a fuel system by housing two kinds of liquids laminarly in a liquid container and providing a pipeline to the container so as to equilibrate the pressure of respective fuel systems.

CONSTITUTION: The conduit 6 branched from the conduit 4 through which fuel oil is supplied from a feed pump to the injection pump 2 is connected to the container 5 housing required liquid A and a fuel oil B separately by means of the thin film 10. The liquid A is additive for accelerating start-up, for example, and when the liquid is to be supplied immediately before the stoppage of engine, the stop valve 8 is opened, whereupon a pressure from the feed pump acts on the conduits 4 and 6, the container 5, and the conduit 7 and also a negative pressure is produced in the throttled portion 11 due to the inflow of fuel oil into the pump 2, so that an appropriate amount of the liquid A is sucked up from the nozzle 12.