It may be time to replace your Cummins injectors if you are experiencing poor, idle, rough engine performance, reduced engine power, reduced engine efficiency or if the exhaust gives of unburnt fuel. The principal role of these injectors is to spray the right amount of fuel into the combustion chamber of the engine just before the piston moves down, mixing fuel and air to run the engine. If your vehicle’s fuel injectors are failing or not working properly, the right mix of fuel and air will not be achieved, something that will lead to issues in your engine.