A worn precision pair loses tight clearance, leading to internal leakage and insufficient fuel delivery. As a result, injection pressure drops and proper atomization is not achieved.
A very common real case occurs during changeover from heavy fuel oil (HFO) to diesel oil (MDO/MGO). Heavy fuel has higher viscosity and can still provide some sealing effect, even with worn components. However, when switching to low-viscosity diesel fuel, leakage increases significantly inside the plunger–barrel pair.
👉 Result: insufficient injection pressure and the engine may fail to start.
This is why the condition of the fuel injection components becomes critical, especially during fuel changeover operations.
Understanding this relationship helps prevent unexpected starting failures and improves overall engine reliability.