You can't be turning the pump on and off. There is no accumulator to maintain the pressure when the pump is off. The bucket that the fuel pump sits in is to insure there is no fuel starvation when the fuel tank levels are low and the fuel is sloshing around. That is why the fuel return is dumped into the bucket. Walro recommends that a new fuel pump installation should start with 1/2 tank of fuel. They want the fuel pump wet and primed when it first starts.
So, here is how the fuel goes: starts at the pump, goes to the connection on one of the injectors, crosses through the short hose to the other fuel injector, then returns to the fuel filter. Why the fuel filter at the end of the loop? because inside the fuel filter is a pressure regulator that maintain the 58 psi fuel pressure in the loop. The only section of hose that is not under pressure is the fuel return line, beyond the pressure regulator, that dumps the unused fuel into the bucket where the fuel pump resides.
Thanks for the clear explanation! I wasn't aware that the return fuel was dumped back into the pump pickup bucket. Makes sense, but I wonder if that may be a contributor to the suspected heat-related pump failures?
If the fuel is "over-heated" by its trip past the engine then returned directly to the pump pick-up location, it stands to reason that over time with a hot engine on a hot day, that heat could build up faster (in the fuel going through the pump) than one might expect of the larger volume of fuel in the tank. If so, it may help explain why insulating the lines near the engine is reported to help with pump life.
