KOMATSU fuel Injectors. Fuel injectors are nozzles that deliver a high-pressure spray of fuel that mixes with air on the intake stroke of your engine's pistons.While fuel injection is a lot more reliable overall, injectors have been known to clog or fail.All diesel engines use fuel injection by design. Petrol engines can use gasoline direct injection, where the fuel is directly delivered into the combustion chamber, or indirect injection where the fuel is mixed with air before the intake stroke.