If you have bleed it with the bleeders facing up and you don't have much pedal....very likely a master cylinder. Often a bad master cylinder won't have any pedal, but not always. Could be a loose line, or worn brake piston bore sucking air or fitting sucking air. Sometimes when people bleed the system and they are using the pedal, the pedal doesn't have enough throw and it doesn't move enough fluid to bleed the system properly.