柴油机喷油时间过早或过晚将使发动机功率下降。喷油过早会冒白烟，并伴随敲击声，起动时起动机常受反转阻力；喷油过晚则冒黑烟，加速缓慢。为了保证最佳喷油时刻，各制造厂家在正时齿轮上都打有专门标记供装配时使用。如飞轮上没有记号或刻线（或模糊不清），要想使喷油正时 Diesel fuel injection time too early or too late will make the engine power down. Injecting too early will take white smoke, and accompanied by the percussion sound, starter often start to reverse resistance; fuel injection is too dark, accelerate slowly. In order to ensure the best fuel injection time, the manufacturer in the timing gear are marked with a dedicated mark for assembly. If the flywheel is not marked or engraved (or blurred), to make fuel injection timing