At the start of every print, the printer will purge some filament from nozzle 1, then switch and do the same for nozzle 2. However, nozzle 2 is never purged for long enough for filament to come out. I used a stopwatch and watched: nozzle 1 spent about 16 second purging about 195mm of filament, then nozzle 2 spent about 8 seconds purging 0mm of filament. (This was after priming both nozzles before starting a print.)
It doesn't make sense to me as the gcode for both nozzles is the same.
M117 Purging... ; LCD status message T0 ; select this extruder first G1 E0 F100 ; undo retraction G92 E-15 ; set extruder negative amount to purge G1 E0 F100 ; purge XXmm of filament T1 ; switch to second extruder G1 E0 F100 ; undo retraction G92 E-15 ; set extruder negative amount to purge G1 E0 F100 ; purge XXmm of filament G1 Z0.5 ; clear bed (barely) G1 X100 Y0 F5000 ; move above bed to shear off filament
This doesn't affect the print since by the time it does the skirt for nozzle 2 it's extruding.