my 1995 4x4 blazer is hard to start u have to pump the gas its throwing a knock sensor code what could this be please help

 

Could be fuel pump, could be fuel pressure regulator, could be distributor could need a tune up real bad, could be all sorts of issues, you need to get it scanned and find out what codes it is throwing even if you dont have an SES light on. It can have more than one code in it's memory so that is the only way tom really check it.