Abstract: A water injection Diesel engine undergoes stable combustion even though the amount of water to be injected is relatively large. A common fuel injection valve of the water injection Diesel engine injects fuel and water into a cylinder of the engine. A change-over valve and a control valve are provided for alternately opening and closing a fuel feed passage and a water feed passage connected to a water passage of the fuel injection valve. Alternatively, control valves are provided for effectively opening and closing a water feed and a fuel feed which are connected discretely with a fuel passage within the fuel injection valve. In each embodiment, a multi-layered column of alternating layers of water and fuel is formed in the fuel injection valve so as to be injected during a single fuel injection cycle.

Abstract: An improved fuel/water injection device of a diesel engine injects both fuel and water into a combustion chamber of the engine from the same fuel injection valve in a manner which reduces both the black smoke and NO.sub.x in the exhaust gas. During each injection, 5% or more and 75% or less of the total amount of fuel is firstly injected; subsequently, a total amount of water is injected; and finally, the remaining fuel is injected.