Here's a question that my factory service manual can't answer. The cannister-type fuel filter on my 3.8L 2002 T&C minivan has three fuel lines: one supplying fuel from the tank to the filter, one directing fuel back to the tank from the filter, and one supplying fuel to the engine from the filter. As I understand it, the pressure regulator in the pump module controls pressure to around 50 psi. If the excess fuel is kept in the tank by being discarded by the regulator, why is there a return line from the fuel filter back to the fuel tank? Does the regulator control pressure through the fuel returning from the filter? If so...why?