How can the Bosch 044 fuel pump, when installed inline in series with an in-tank fuel pump, flow more when it is drawing through a much smaller fuel pump?
You have a very good question there. Think of each pump having a low pressure side (inlet) and a high pressure side (outlet). The low pressure side of the in-tank pump is at about zero psi, the high pressure side will only be at a few psi since the Bosch 044 pump is not providing any real restriction. Then, the Bosch 044 pump with the inlet, at a few psi, can push more fuel at higher pressures than it would be able to otherwise. Basically, the “boost” from the in-tank pump shifts the Bosch fuel pump’s entire output curve up, especially critical at the higher pressures. Basically a positive displacement fuel pump creates flow and the fuel pressure regulator causes a “restriction” after the fuel injectors to create pressure. Fuel flow (volume per time) is independant of fuel pressure (force per area). The in-tank pump is creating low pressure and high volume. Then the Bosch 044 pump would create higher pressure and have to work less to make higher volume. This gives the Bosch 044 pump th
