A method of assembling a fuel injector

A method of assembling a fuel injector (8) comprising a fuel injector body having an accumulator volume (22) defined therein is described. The method comprises: providing an encapsulated actuator arrangement (29a) having a piezoelectric actuator stack (29) and electrical connector means (34,36), wherein the stack (29) is encapsulated in a sleeve member (30); providing a volume of sealing material (42) in the region of the electrical connector means (34,36); locating the encapsulated actuator arrangement (29a) in the accumulator volume (22); applying heat indirectly to the volume of sealing material (42) so as to soften the volume of sealing material; and applying pressure to the encapsulated actuator arrangement (29a) such that the volume of sealing material (42) deforms to form a substantially fluid-tight seal (38) between the encapsulated actuator arrangement (29a) and the accumulator volume (22) in the region of the electrical connector means (34,36).