Please refer to chaim's post just above my response, where chaim quotes Felder as saying:
as Don and Glenn and I worked on the lyrics
which chaim states is taken from a 1980 interview.
Obviously 'worked on' is not the same as 'wrote' but this is the only example of a quote from him I have ever seen which even hints that he had any involvement with the song's lyrics. He no longer claims this in any way.