A fuel pump (10) for a vehicular diesel fuel pump member having a control valve assembly which includes a housing having a control valve chamber (20), and an actuatable control valve (34) disposed in the control valve chamber. The control valve includes a piston valve body axially movable between first and second positions. A valve stop (44) is disposed in the housing adjacent the control valve chamber, and a piston valve body seat (90) contacts the valve stop whenever the piston valve body is in the second position. A first control valve spring (70) biases the piston valve body toward an unactuated position and a second spring biases the piston valve body into damped engagement with the valve stop.