09 freightliner cascadia ringing noise

there is a pressure regulator valve on high pressure pump..

 

If you hear a ringing noise, answer the phone.

 

Sounds like an o ring on a injector. Check to see where the return lines come back to your fuel tanks, if the return line is below your fuel level in the fuel tank look in your fuel tank, if you see small bubbles dancing across your fuel you have a bad o ring on one or more of your injectors. This will not show a code because the injectors are working fine. It will idle fine, however under a slight load, compression will blow past the bad o ring and the rail pressure will go ape #### and blow the fuel out of the lines, as soon as it goes back to idle it's fine again.