Can't get good front brake pressure on a 96 Toyota T100 replaced master cylinder

Have a helper pump - then hold brake pedal down .. Loosen the brake line at the master cylinder to see how much pressure is at that point.... REAR brake 'load sensing' valve will not cause this problem. IF master cylinder *bench bleeding* was not performed OR was not performed correctly - that is likely causing the problem. Sometimes it takes SEVERAL attempts to completely remove ALL air from the system.