求翻译：1、单柱塞喷油泵 　　2、泵喷嘴系统：泵喷嘴系统的泵喷嘴直接安装在气缸顶部，喷油泵与油嘴是一体的。它由发动机凸轮轴驱动，每一个泵喷嘴都配有一个电磁阀对喷射始点和喷油结束点进行控制。当电磁阀打开时，泵喷嘴将燃油送入回油孔。当电磁阀关闭时，泵喷嘴将燃油直接喷入发动机气缸。关闭时间点决定着喷油始点，关闭持续的时间则决定着喷油量。是什么意思？

Single plunger injection pump, the pump-nozzle system: pump nozzle of the pump-nozzle system mounted directly on top of the cylinder, fuel injection pump and nozzle are one. Driven by the engine camshaft, each pump nozzle with a solenoid valve to control the injection timing and fuel injection end p