Kubota M108S, Workshop Manual

Page: 111 / 523

1-M16
M108S, WSM ENGINE
[3] RAIL
The function of the rail (2) is to distribute fuel
pressurized by the supply pump to each cylinder injector.
The component parts are the pressure limiter (1) and the
rail pressure sensor (3). The function of the pressure
limiter (1) is to open the valve to release fuel pressure if
the fuel pressure in the rail becomes abnormally high.
The function of the rail pressure sensor (3) is to detect
the fuel pressure in the rail.
■
Pressure Limiter
The pressure limiter (1) opens to release the fuel
pressure if abnormally high pressure is generated (B). If
fuel pressure within the rail (2) becomes abnormally high,
the pressure limiter (1) operates (opens). It resumes
operation (closes) after the pressure falls to a certain
level (A). Fuel released by the pressure limiter (1)
returns to the fuel tank.
The operating pressures for the pressure limiter (1)
are approximately 200 MPa (2040 kgf/cm
2
, 29000 psi)
for the valve opening pressure, and approximately 50
MPa (510 kgf/cm
2
, 7300 psi) for the valve closing
pressure.
■
Rail Pressure Sensor
The rail pressure sensor (3) is installed on the rail (2).
It detects the fuel pressure in the rail (2) and sends a
signal to the engine ECU. This is a semi-conductor
sensor that uses the piezo-electric effect of the electrical
resistance varying when fuel pressure is applied to a
silicon element.
W1016627
(1) Pressure Limiter
(2) Rail
(3) Rail Pressure Sensor
(4) Valve (Open)
(5) Valve (Close)
(6) Rail Pressure
(7) Output Voltage
(8) Rail Pressure A : Return Pressure
B : Abnormally High Pressure
C : Output Voltage-Rail
Pressure Characteristic
KiSC issued 06, 2007 A