1993 Nissan Cefiro Clutch not working

I recently developed a problem when trying to put the car in first gear and reverse gear and decided to change out the rubber kits for my clutch master and slave cylinders as the fluid in the reservoir was turning black. I then drained all of the old fluid and added fresh fluid and bled out the system. While bleeding the system I noticed that I would have to pump the pedal a few times to build pressure and to get the piston in the slave cylinder to move forward. I am still experiencing the same problem and was wondering if one of the cylinders would need changing and how would I be able to tell which one?