A fuel injection control assembly for a cylinder-injected engine includes a mean fuel pressure calculating element for calculating mean fuel pressure, a fuel pressure regulator for adjusting the fuel pressure, an injection pulse calculating element for calculating an injection pulse duration for an injector based on the mean fuel pressure, and a cycle modifying element for modifying the calculation cycle for the mean fuel pressure in response to the running speed of the engine or of a high-pressure pump, the cycle modifying element setting the calculation cycle to a length greater than or equal to a running cycle of the high-pressure pump to ensure that the number of times that fuel pressure is detected within each calculation cycle of the mean fuel pressure calculating element is greater than or equal to a predetermined number of times.