A plunger for well casings and tubulars comprising: an upper valve rod segment slideably positioned within the plunger body; a valve rod tube slideably positioned in the lower end of the plunger body; a lower valve rod segment slideably positioned in the valve rod tube; a spring positioned between the upper and lower valve rod segments; and a valve element on the upper valve rod segment for closing the plunger flow passage when the upper valve rod segment moves to a closing position. The plunger preferably also comprises an exterior flexible sealing member and a sealing member actuator operated by the valve rod tube. A shield is also preferably provided in the plunger body to prevent premature closure of the valve element.