The liquid phase LPG injection (LPLi) system (the third generation technology) has been considered as one of the next generation fuel supply systems for LPG vehicles, since it has a very strong potential to accomplish the higher power, higher efficiency, and lower emission characteristics than the mixer type(the second generation technology) fuel supply system. To investigate the durability property of core part of injector in liquid phase LPG injection system, leakage test, SEM test of injectors and analysis of unvaporized fuel components with various LPG fuel qualities were tested. The experimental results showed that no serious problem in durability test using favorable LPG fuel quality, while high leakage amount due to the large scratches in the needle and nozzle of the injector were found using LPG fuel with highly containing olefin components, especially butadiene species.