Yamaha F400A 2022 - Direct Injection Pump

Fuel system
2-48
Direct injection pump
Each direct injection pump “1”, which has a mechanically driven built-in plunger “2” and an electrically
driven built-in solenoid “3”, pressurizes the fuel to the high pressure required for direction injection.
The fuel inside the pump is sent through the mesh filter “4” and damper “5” to the solenoid chamber
and plunger chamber. The pressure of the fuel is increased by the plunger that is driven by the cam-
shaft “6” and the fuel is sent to the fuel rail through the check valve “7”. To prevent the fuel from flowing
back from the inlet of the plunger chamber at this time and reducing the pressure, the solenoid blocks
the passage at the inlet “a” of the plunger chamber while the fuel is being pressurized. During 1 turn
of the camshaft, the fuel is pressurized 4 times and the solenoid repeatedly opens and closes the pas-
sage each time. Conversely, if the fuel pressure in the fuel rail is too high, the fuel returns through the
return valve “8”.
In addition, feedback control is carried out based on the information from the fuel pressure sensor (di-
rect injection pump), and the operation of the solenoid is controlled to change the flow volume and
adjust the fuel pressure.
1
2
3
4
5
8
7
6
a
C
A
B
A. From vapor separator
B. To fuel rail
C. Fuel flow