Fuel injector

A variable orifice nozzle assembly (12) of a fuel injector (10) having an upper set of spray holes (18) and a lower set of spray holes (20), and being provided with an outer valve member (36) controlling the upper holes (18) and, an inner valve member (40) coaxially slidably arranged inside the outer valve member (36) for controlling the lower holes (18). The outer (36) and the inner valve members (40) are able to be independently translated between a closed position (PC) prohibiting fuel spray and an open position (PO) enabling fuel spray and, the nozzle assembly (12) is provided with an expansion means (50,52,54, 56, 58) enlarging the outer valve member (36) when being in closed position (PC).