Fi System - Yamaha XF50W Service Manual

EAS00897

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 only 250 kPa (2.5 kg/cm
when the energizing signal from the ECU energizes the fuel injector, the fuel passage opens, caus-
ing 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 crankshaft position sensor, intake air pressure sensor, intake temperature sensor and engine
temperature sensor enable the ECU to determine the injection duration. The injection timing is deter-
mined 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.
Fuel pump
1
Fuel injector
2
Ignition coil
3
ECU
4
Catalytic converter
5
Coolant temperature sensor
6
Crankshaft position sensor
7
Intake air pressure sensor
8
Throttle body assembly
9
Intake air temperature sensor
0
FEATURES
Air filter case
q
ISC (idle speed control) valve
w
Throttle position sensor
e
A Fuel system
B Air system
C Control system
1-3
2
, 35.6 psi). Accordingly,