Originally Posted by Kuhlrover

This is intended to maximize the amount of diesel purge that is being circulated through the pump and injectors. Without the return line going back to the source bottle, only a fraction of the diesel purge will be introduced to the system with the majority going to the return loop back to the tank. It is also standard practice to replace the fuel filters after the diesel purge procedure. The secondary fuel filter should not let any big particle past that could damage the system.

TimK