FUEL INJECTOR HAVING VALVE STACK WITH VENTED BACK-UP PLATE FOR CHECK SEAL RETENTION

A fuel injector includes a valve stack forming a seal cavity, and an outlet check extending through the seal cavity. A check seal is positioned within the seal cavity and seals about the outlet check. The valve stack also includes a back-up plate trapping the check seal within the seal cavity, such that a crevice is formed within the seal cavity between the check seal and the back-up plate. The back-up plate has a vent formed therein that fluidly connects the crevice to a drain.