IIS 7 and Above
Application pool stops automatically in IIS7
Last post Nov 11, 2013 03:00 PM by VamsiR
Aug 09, 2012 08:05 AM|Hiteshv|LINK
Aug 09, 2012 09:12 AM|peterviola|LINK
The system event log will provide insight as to why the app pool is stopping. If you are using a custom user account for the app pool identity make sure that user account has permissions on the root folder for the site and is added to the IIS_WPG user group.
Here is more information about setting app pool identities.
Aug 14, 2012 03:25 AM|Lloydz|LINK
Have you checked event viewer to see if there's any related events logged? If nothing logged in event viewer, please check http.sys logs(located at %windir%\system32\logfiles\httperr) for detailed reason. Here's a great article that elaborates the general
steps for troubleshooting 503 service unavailable:
Where did my IIS7 server go? Troubleshooting 503 "service unavailable" errors
Nov 11, 2013 03:00 PM|VamsiR|LINK
This was because the password was changed recently for the Identity under which the application pool was trying to run. Fix was to go to the IIS Manager-> Application Pool -> Advanced Settings -> Process Model -> Identity and set the password to the new