We have experienced some issues with the fuel flushing or the control system delay for fuel flushing in the past on the W20V34SG machines with both WECs8000 or UNIC . The exhaust temperatures near the main fuel gas venting valve does not rise quickly after a 48 hours or longer without operating the engine.
In some cases the venting valve was not opening due to either the solenoid valve failure or the actuator was leaking air and needed to be rebuilt. In other cases the fuel pressure and or the main fuel vent valve open duration needed to be increased to vent the engine fuel system a little more.