A fuel injection system includes a fuel injector (6) having a body, a needle valve (5) movably provided in the body and a fuel accumulator having two chambers (3, 4) for storing a fuel at high and low pressures. An injection chamber (19) is formed in the injector lower body and a control chamber (22) is formed in the injector upper body. An injection passage (17) connects the high pressure chamber (3) with the injection chamber (18) and a control passage (21) connects the low pressure chamber (4) with the control chamber (22). The needle valve (5) is lifted upon leaking of the fuel to the accumulator from the control chamber (22) and the fuel is injected from the injection chamber (19) upon lifting of the needle valve (5). The fuel is recycled to the fuel tank from the control chamber (22).