Subaru 2002 Impreza Service Manual page 59

FUEL LINE
Fuel Injection (Fuel System)
B: PRESSURE REGULATOR
The pressure regulator is installed at the injector end of the fuel supply line. It has a fuel chamber
and spring chamber separated by a diaphragm. Fuel chamber is connected to the fuel supply
line and the spring chamber is connected to the intake manifold. Fuel chamber also has a relief
valve connected to the fuel return line through which fuel returns to the fuel tank. When the intake
manifold vacuum increases, the diaphragm is pulled and the relief valve opens to decrease the
fuel supply line pressure (or fuel injection pressure). When the intake manifold vacuum decreases,
the diaphragm is pushed by the spring to increase the fuel supply line pressure. Thus, the differ-
ence between the fuel injection pressure and the intake manifold vacuum is kept at a constant level
of 294 kPa (3.00 kgf/cm2, 43.0 psi) to precisely control the amount of injected fuel.
A
0
A: To intake manifold
B: Fuel IN
C: FuelOUT
B
NF0387
(1) Relief valve
(2) Diaphragm
FU-9