A system for preventing rotation of a tappet includes a tappet having an outer casing and a central axis which is configured to reciprocate linearly along the central axis. The outer casing includes a flat portion having a length along the central axis and having a width. Additionally, the system includes a lock bar fixed in position relative to the linear oscillation of the outer casing. The lock bar is positioned in proximity to the flat portion of the outer casing. Upon rotation of the outer casing about the central axis, the lock bar is configured to come into contact with the cuter casing and inhibit additional rotation of the outer casing.

A system for preventing rotation of a tappet includes a tappet having an outer casing and a central axis which is configured to reciprocate linearly along the central axis. The outer casing includes a flat portion having a length along the central axis and having a width. Additionally, the system includes a lock bar fixed in position relative to the linear oscillation of the outer casing. The lock bar is positioned in proximity to the flat portion of the outer casing. Upon rotation of the outer casing about the central axis, the lock bar is configured to come into contact with the cuter casing and inhibit additional rotation of the outer casing.

A fuel pump assembly for an internal combustion engine includes a fuel pump housing, a cylindrical bore defined in the fuel pump housing, and a tappet assembly received in the cylindrical bore. The tappet assembly includes a one-piece shoe having a recess disposed in a bottom portion thereof, and a roller that is partially received within the recess and configured to rotate about a roller axis.