||This article presents an original method of using elastic waves of acoustic emission (AE) to assess the technical condition of nozzles in marine diesel engines. The developed method makes it possible to detect the early stages of wear by friction of the needle-nozzle pair. The phenomenon of AE and the possibility of its use in evaluating the condition of marine diesel-engine injectors are discussed. Experiments are presented in which the AEs were used to evaluate the condition of both a new injector and an injector where galling of the needle-nozzle pair is developing. The measurements were processed by time–frequency analysis and wavelet transformation.