Sync Bookmarks, passwords in Firefox using Firefox Sync

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http://superuser.com – I have used Firefox Sync and successfully setup sync on two devices. It is working fine. The only issue I am seeing is that Bookmarks don't sync up automatically. I need to click on Tools -> Sync Now After clicking on above mentioned button, I immediately see the effect on bookmarks. Is there any configuration using which Firefox sync can run automatically ? (HowTos)