Electronic pressure relief in a mechanically actuated fuel injector

A mechanically actuated electronically controlled fuel injector (10) includes a first electrical actuator (21) that controls the position of a spill valve (22), and a second electrical actuator (31) to control pressure on a closing hydraulic surface (34) associated with a nozzle check valve (32). The fuel injector (10) is actuated via rotation of a cam (9) to move a plunger (15) to displace fuel from a fuel pressurization chamber (17) either to a spill passage (20) or at high pressure out of a nozzle outlet (12) of the fuel injector (10) for an injection event. Pressure in the fuel injector (10) is moderated when the plunger (15) is moving and the nozzle check valve (32) is in a closed position by briefly cracking open the spill valve (22) to relieve some pressure during the dwell (D) between injection events, such as between a large main injection event (51) and a small close coupled post injection event (52). This strategy allows for longer dwell times between injection events as well as smaller injection quantities in the post-injection.