Pompe à huile haute pression usée

On engines using high pressure oil to actuate the fuel injectors, the pump generating that pressure, worn until it cannot reach or hold the commanded value. This is a separate circuit from the engine's lubrication system and runs at pressures an order of magnitude higher; confusing the two sends the diagnosis to the wrong pump entirely.

Its failure shows worst where demand is highest — cranking, cold starts and full load — because a worn pump can still satisfy a light demand. So the complaint is a long crank or a no-start when cold with an engine that runs acceptably once going, and the stored codes name injection pressure rather than the pump.

Distinguish it from a leak in the circuit, which presents identically. A pump that cannot build pressure and a circuit that cannot hold it both show as commanded pressure not achieved. The difference is in how the pressure behaves when the pump stops: a circuit that bleeds down rapidly has a leak, while one that holds points at the pump's ability to generate. Test that before ordering, because the pump is the expensive part and a failed seal or fitting is the commoner fault.