If you are trying to draw ink down from below the capping station, you should be able to pull the syringe out, let go and it will snap back. If you pull the syringe, let go and it does not snap back, your cap top is not sealing with the head properly. Check to make sure the capping station is seated properly and that it is as clean as can be. Also check for any cracks or divots in the rubber seal on the cap top. If the seal is damaged you will need to get a new one. Sometimes just wetting the cap top with cleaning solution will help create the initial seal you need to get it going. Also make sure the head is not tilted or higher than the other heads making it unable to come in contact with the cap.