Be careful to not get dirt in the injection pump or injector pipes during this procedure! The first step in this process is to remove the plastic cover from the top of the engine. For D5244 T to T3 engines, release the clamps and remove the charge air hose that is connected to the intake manifold, remove the crankcase breather hose from the cylinder head cover, pull the connectors from the glow plugs, and make sure the areas around the high-pressure fuel pipe unions are clean. Undo unions and take off high-pressure fuel lines, discard them and get ready for fuel spillage by plugging ports. Disconnect the fuel return hoses from the injectors, take note of their location and disconnect the injector wiring plugs. Unscrew the screws holding each injector clamp in place, remove the injectors, removing the sealing washers and other parts, marking injectors for identification if they are to be refitted. For D5244 T4 to T7 engines, remove the cross-stay between the suspension turrets, ensure the rubber shield over the fuel injectors is removed and ensure cleanliness around the high-pressure fuel pipe unions. Follow similar steps to remove the high pressure fuel pipes, disconnect the return hoses and wiring plugs, unscrew the injector clamps and recover the metal washers. Store injectors in an upright position if they are to be refitted. During refitting, make sure injectors and seats are clean and install new parts, tightening screws evenly. Install new high pressure pipes and tighten unions to specified torque, followed by the injector retaining screws. Check the condition of fuel return hoses including 'Class' identification number for D5244 T to T3 engines and software updates to be carried out for new injectors for D5244 T to T7 engines. Finally, step on the accelerator pedal and start the engine, checking for fuel leaks after running at fast idle to purge trapped air.