Yamaha MBK MW125 2014, Service Manual

Page: 12 / 380

FEATURES
1-3
EAS30617
FI SYSTEM
The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the
fuel pressure that is applied to the fuel injector at a certain level. Accordingly, when the energizing signal
from the ECU energizes the fuel injector, the fuel passage opens, causing the fuel to be injected into
the intake manifold only during the time the passage remains open. Therefore, the longer the length of
time the fuel injector is energized (injection duration), the greater the volume of fuel that is supplied.
Conversely, the shorter the length of time the fuel injector is energized (injection duration), the lesser
the volume of fuel that is supplied.
The injection duration and the injection timing are controlled by the ECU. Signals that are input from the
throttle position sensor, coolant temperature sensor, lean angle sensor, crankshaft position sensor, in-
take air pressure sensor, intake air temperature sensor, speed sensor and O
2
sensor enable the ECU
to determine the injection duration. The injection timing is determined through the signals from the
crankshaft position sensor. As a result, the volume of fuel that is required by the engine can be supplied
at all times in accordance with the driving conditions.
1
13
B
11
12
10
3
A
2
9
4
C
6
5
7
8
1. Fuel pump
2. Injector
3. Coolant temperature sensor
4. ECU (engine control unit)
5. Throttle position sensor
6. Speed sensor
7. Lean angle sensor
8. Intake air temperature sensor
9. O
2
sensor
10. Crankshaft position sensor
11. Throttle body
12. Intake air pressure sensor
13. Air filter case
A. Fuel system
B. Air system
C. Control system