We study the time-dependent backscattered current produced in a quantum wire when a local barrier is suddenly switched on. Previous investigations are improved by taking into account the finite length of the device. We establish two different regimes in terms of the relationship between the energy scales associated with the voltage and the length of the system. We show how previous results, valid for wires of infinite length, are modified by the finite size of the system. In particular, our study reveals a rich pattern of temporal steps within which the current suffers an initial relaxation followed by temporary revivals. By employing both analytical and numerical methods we describe peculiar features of this structure. From this analysis one concludes that our results render a recently proposed approach to the determination of the Luttinger parameter, K, more realistic.Facultad de Ciencias ExactasInstituto de Física La Plata