Qualcast Trojan starter cord snapped?

Hi all,
The rip cord with toggle pulled to start up the engine has snapped.
I've taken the metal cover off the top of the engine (can't tell what make it is - no name but I assume its a Techumesh or a Briggs & Stratton as thats what I find when I search for an engine operating manual).
I've fed it throught the eyelet and knotted the cord, manually wound it up and refitted the cover. It cranks over the engine but the cord doesn't rewind onto the spool. Removed cover again and manually wound it on - this time I hear the spring slipping every other turn. How can I get it to draw the cord back onto the spool?