The invention relates to a fuel injector having a coupler. The reciprocating movement of an actuator is transmitted by the coupler to a pin-shaped injection valve member which is guided into the nozzle body. The coupler has a valve piston and a coupler sleeve, and the valve piston is displaced in the inner diameter area of the coupler sleeve. The inner diameter of the coupler sleeve is greater than the outer diameter of the injection valve member. The difference between the inner diameter of the coupler housing and the outer diameter of the injection valve member is 0.2 mm or less.