WCF service with Full Memory Error (Memory gates checking failed because the free memory) - How to resolve

Try setting minFreeMemoryPercentageToActivateService to 0 in yourweb.config for WCF Host, as suggested in this answer

instead of changing WCF config value, Try to know which process workingset memory high, try see that if its really requires

Powershellcommand>> get-process | Sort-Object WS -desc >c:\process.txt 

Also to know whether which processid is pointing to IIS App pool

cmd.exe>> %systemroot%\system32\inetsrv\AppCmd.exe list wp 

By allowing zero in config, this might be able to activate may corrupt the state of service for memory not available reason - that could be not so straight forward in nature :(

My 2 cents...

There are situations when changing the web.config is not an option. In our case we solved this by increasing the server's memory from 8GB to 16GB.