A common-rail fuel injection system for an engine includes a fuel injection device for injecting high pressure fuel from a common rail into the engine. A pumping chamber is connected to the common rail. A fuel feed device serves to feed fuel to the pumping chamber. A plunger moves upward and downward in accordance with rotation of an output shaft of the engine. The plunger defines a part of the pumping chamber. A relief valve serves to selectively return fuel from the pumping chamber to a low pressure side via a fuel return passage. The relief valve is urged toward its closed position by a pressure of the fuel in the pumping chamber. A valve closing device serves to close the relief valve. A fuel pumping control device serves to drive and control the valve closing device at a given timing to close the relief valve, thereby enabling a pressure in the pumping chamber to increase in accordance with upward movement of the plunger and pumping a given amount of fuel from the pumping chamber to the common rail. An engine speed detecting device serves to detect a rotational speed of the output shaft of the engine. In cases where an engine rotational speed detected by the engine speed detecting means is equal to or higher than a predetermined reference speed, a fuel feed suspending device serves to suspend fuel feed to the pumping chamber by the fuel feed means.