The invention relates to a system for injecting a liquid into a body, comprising an implantable chamber disposed under the skin and an injection device including: a base bearing an injection needle having a free end that is intended to be inserted into the chamber an injection conduit connected to the needle means for extracting the needle means that can be actuated to generate excess pressure in the injection conduit synchronization means between the extraction means and the generation means for actuating the generation means during a needle extraction phase. The synchronization means can essentially only actuate the generation means when the free end of the needle is located in the chamber during the needle extraction phase.
