An engine, comprising a cylinder head, an engine camshaft and a variable stroke direct injection fuel pump system, the system comprising: a direct injection fuel pump including a stroke member and configured to pump a quantity of fuel based on a stroke of the stroke member; a variable fuel pump actuator assembly configured to activate the DI fuel pump, the variable fuel pump actuator assembly comprising: an actuator member in fluid communication with a control valve and configured to actuate the stroke member in response to a pressure of hydraulic fluid at the actuator member, the control valve configured to control the fluid pressure at the actuator member by controlling a flow of hydraulic fluid to the actuator member, and a hydraulic fluid pump configured to pump the hydraulic fluid to the control valve and selectively to the actuator member, in response to actuation by one or more lobes of said camshaft; and an engine control unit configured to control a variable stroke of the stroke member by controlling the control valve to deliver a controlled amount of hydraulic fluid pressure to the actuator member based on one or more operating parameters of the engine, said engine being characterized in that: said variable fuel pump actuator assembly is associated with said cylinder head of the engine, said actuator member, said control valve and said hydraulic fluid pump are positioned at least partially in the cylinder head, said system further comprises a pump fluid passage in the cylinder head fluidly coupling the hydraulic fluid pump to the control valve, and an actuator member passage in the cylinder head fluidly coupling the control valve to the actuator member, said control valve being able to communicate said pump fluid passage to a passage connected to an accumulator line, so as to divert a predetermined amount of pumped fluid from reaching the actuator member. a direct injection fuel pump including a stroke member and configured to pump a quantity of fuel based on a stroke of the stroke member; a variable fuel pump actuator assembly configured to activate the DI fuel pump, the variable fuel pump actuator assembly comprising: an actuator member in fluid communication with a control valve and configured to actuate the stroke member in response to a pressure of hydraulic fluid at the actuator member, the control valve configured to control the fluid pressure at the actuator member by controlling a flow of hydraulic fluid to the actuator member, and a hydraulic fluid pump configured to pump the hydraulic fluid to the control valve and selectively to the actuator member, in response to actuation by one or more lobes of said camshaft; and an actuator member in fluid communication with a control valve and configured to actuate the stroke member in response to a pressure of hydraulic fluid at the actuator member, the control valve configured to control the fluid pressure at the actuator member by controlling a flow of hydraulic fluid to the actuator member, and a hydraulic fluid pump configured to pump the hydraulic fluid to the control valve and selectively to the actuator member, in response to actuation by one or more lobes of said camshaft; and an engine control unit configured to control a variable stroke of the stroke member by controlling the control valve to deliver a controlled amount of hydraulic fluid pressure to the actuator member based on one or more operating parameters of the engine, said variable fuel pump actuator assembly is associated with said cylinder head of the engine, said actuator member, said control valve and said hydraulic fluid pump are positioned at least partially in the cylinder head, said system further comprises a pump fluid passage in the cylinder head fluidly coupling the hydraulic fluid pump to the control valve, and an actuator member passage in the cylinder head fluidly coupling the control valve to the actuator member, said control valve being able to communicate said pump fluid passage to a passage connected to an accumulator line, so as to divert a predetermined amount of pumped fluid from reaching the actuator member.