Diesel injectors can suffer from the same kinds of aliments as petrol injectors, including varnish deposits, clogging, wear and leakage. Because diesel injectors operate at a much higher pressure than petrol injectors, their opening pressure can also drop over time.
You may find that one or more injectors need replacement nozzle tips. As the spray holes wear or become clogged, spray pattern and fuel atomization are affected as well. This in turn, can have an adverse effect on fuel economy, starting, noise, smoke and emissions. Nozzles tips also lose their temper from long-term exposures to operating temperatures, which means they will naturally wear over time and useage.