Tuesday's postponement had Fuglesang disappointed but hopeful of a launch on Wednesday.
"Back at my room after 4 hours on my back in the shuttle. A bit sore. Hungry. Bad luck, but not too disappointed. This is the way this is. Gunning for tomorrow!," Fuglesang wrote on the microblog service Twitter after the launch attempt was called off on Tuesday morning.
After the most recent delay he tweeted: " We were just told that it won't be possible today either. Technical problem. More later. Bad luck again, but perhaps this means we'll be able to have dinner with our families."
NASA is planning another attempt to launch Discovery at 06:22 CET. But before that the faulty valve will be properly checked.