Despite the development of hybrid and electric vehicles, a many-million population of cars with combustion engines, and particularly CI engines occurs on the roads. Also, many stationary CI engines are still utilized. Despite their improved technologies and characteristics the modern CI engines negatively affect an environment due to cold starting problems. Below 0 °C, engine starts are problematic due to the decreased battery performance and the spray characteristics, the increased ignition delay time, and the engine oil viscosity. Therefore, various glow plugs are applied to facilitate this process. Types, features, and applications of glow plugs in various engines have been discussed in the paper. One case of failure of glow plug has been presented in the article, including the cause of it.