Mechanical injection systems are devices used in internal combustion engines to deliver fuel into the combustion chamber. They operate based on mechanical principles, using components like pumps, injectors, and nozzles to ensure the right amount of fuel is injected at the right time. This system relies on pressure and timing rather than electronic controls, making it simpler and often more reliable in certain conditions. These systems are commonly found in older vehicles and some industrial engines. They can be adjusted for different fuel types and performance needs, providing flexibility. However, they may lack the precision and efficiency of modern electronic fuel injection systems, which use sensors and computers for optimal performance.