Can Firefox Bookmarks sync with Google Bookmarks?

There are various plug-ins that add this feature, I like gmarks which doesn't actually synchronise them but adds an extra gmarks menu next to the bookmarks.

gmarks does not work anymore..One other solution you can try is though this is not for sync but for managing bookmarks directly through google bookmarks

First you need to import your bookmarks into Diigo (make sure bookmarks are public)

Then go to ifttt and run recipe - "Back up Diigo bookmarks to Delicious" https://ifttt.com/recipes/10818-back-up-diigo-bookmarks-to-delicious

Then go to https://www.google.com/bookmarks/deliciousimport to import the bokmarks to google bookmarks