Youfeng Yufeng diesel vehicle can only be started by pulling the water temperature sensor line in the morning. Why?

The control system of EFI gasoline engine judges the water temperature at startup through the water temperature sensor to judge the enrichment degree of fuel injection at startup. Increase the fuel injection amount when the water temperature is too low, and decrease the fuel injection amount when the water temperature is too high. After the water temperature sensor is damaged, it is difficult to control the fuel injection quantity accurately and start it up.