Flow problem with old hot water system

Xray

Hello wetheads!  I am dealing with a gravity system with a newer boiler and a 007 pump.  In the front of a small 3-story building there are 3 1st-floor radiators and 1 2nd-floor radiator which are cold.  In between the problem children are rads connected to the same main which are hot.  I've bled the radiators 'til I'm blue and the radiators get warm, but I get no air, so it ain't an air problem!  I found the aquastat cranked to 210, so I turned it down to 180.  Just for fun ( I'm a fun-loving guy), I wired the pump to run continuously.  It's too soon to know the results, but I've now inherited the baby along with the bathwater.  Any input or suggestions would be enormously appreciated.  Thanks, and....help!!!