Thruster is right. You should know your fuel system like the back of your hand. There's 2 subjects with a 10O% PASS Mark Required. W&B and Fuel Management. To bypass the EDP both valves must be open to allow the electric pump to flow fuel through it. IF either valve OR the spring, malfunctions the EDP won't pump. IF the electric pump is operating it keeps the EDP Diaphragm down with the spring compressed and not stroking. It's quite hard for the lightly spring loaded valves to fail closed But if your Bypass valve didn't seal your EDP wouldn't work properly, so I wonder at the wisdom of fitting it. The FIX creates another Problem. Nev