A fuel injection nozzle assembly for use in an externally ignited internal combustion engine of the air/fuel mixture-compressing type and with fuel injection into a tube through which air is suctioned into the engine, comprising a fuel injection nozzle and heat-insulating means surrounding a part of the nozzle is described. The heat-insulating means surround especially the nozzle part to be inserted into a bore in the wall of the air intake tube. Preferably, the heat-insulating means is a sleeve member made of heat-insulating rubber. The assembly is such that the fuel injection nozzle can be readily removed from the air intake tube. Moreover, both the fuel injection nozzle and the sleeve member can be assembled as a unit.