My power washer is gas powered and it runs until i pull the trigger it cuts right off there seems to be a problem with pressure not building up what's wrong with it if i start it up it will keep running till i start washing , sometimes no water comes out or in spurts

You need to replace your unloader. This is the part that regulates the pressure coming out of your pump. Either contact the manufacturer or Sun Brite Supply (http://store.yahoo.com/cgi-bin/clink?sunbrite+Xru98k+index.html+), they can help you find a replacement.