Hp laserjet 4000-paper not leaving tray

I have a HP jaserjet 4000 and keep getting repeat 13.1.50 paper jams. The paper starts to leave the tray, then stops after moving about 1/2 inch up the paper path. When I open the paper tray, the page is setting on top of the tray. From here I open the paper tray, put the page back in the paper stack, open and close the top cover, put the printer back online and hope it prints out. Any suggestion on which part to replace….