Fuel injection is a system that injects fuel into the engine of a vehicle. The main purpose of fuel injection is to provide better fuel economy and emission control than carburetors. The cost of converting to fuel injection can vary depending on the type of vehicle and the complexity of the conversion. For example, converting a carbureted engine to port fuel injection may cost around $1,500, while converting a carbureted engine to sequential fuel injection could cost upwards of $3,000.