black text in CMYK cannot be saved as C0 M0 Y0 K100

I have an Illustrator file (somewhat older file), and the text is not in pure black which is necessary for printing. normally, i can select such text (outlines) or other elements click on the black button and get it to change to

0 0 0 100

but... it is not working. i can save the change, or just click to another layer, and when i come back to the outlined text... it's back to same old thing...

i have tried to update my version of illustrator, but my imac is abnout 10 years old. but i don't think that can be the problem -- i have done exactly the same recently... just last week, in fact.

can anyone help?

Englisch oder Deutsch