Chrysler DODGE D150 1993 Service Manual page 861

V A C U U M
LINE
PROTECTIVE CAP
INTERNAL
FUEL FILTER
FUEL
PRESSURE
REGULATOR
FUEL RAIL
C O N N E C T O R HOSES J9214-27
Fig. 22 Fuel Pressure Regulator—5.2L Engine
pressure and intake manifold vacuum operate on the
other side. Spring pressure on one side of the dia­
phragm tries to force the return valve closed. Fuel
pressure on other side of diaphragm, with assistance
from manifold vacuum on spring side of diaphragm,
act against spring pressure to open the return valve.
System fuel pressure is the amount of fuel pressure
required to force against spring pressure and unseat
the return valve.
Without vacuum applied to the spring side of the
regulator, the spring is calibrated to open the fuel re­
t u r n outlet. This happens when the pressure differen­
tial between the fuel injectors and the intake
manifold reaches approximately 269 k P a (39 psi).
Since manifold vacuum varies with engine operating
conditions, t h e amount of vacuum applied to the
spring side of the diaphragm varies. For this reason,
fuel pressure varies, depending upon intake manifold
vacuum. With low vacuum, such as during wide open
throttle conditions, minimal vacuum assistance is
available. Full spring pressure is exerted to seal the
fuel outlet. This causes the system pressure to in­
crease. With high vacuum, such as at engine idle or
during vehicle deceleration, fuel pressure on one side
of the diaphragm is balanced by intake manifold
pressure. This is done on the spring side of the dia­
phragm and results in lower system fuel pressure.
5.9L ENGINE
On vehicles equipped with a 5.9L engine, the fuel
filter and fuel pressure regulator are one combined
part (Fig. 23). The fuel filter/fuel pressure regulator
is located on the top of the fuel pump module (Fig.
24). It is pressed into a rubber grommet on module
(Fig. 23).
R e g u l a t o r O p e r a t i o n : The fuel pressure regulator
RUBBER
G R O M M E T
AT PUMP
MODULE
FUEL FILTER/FUEL
PRESSURE REGULATOR
CALIBRATED
SPRINGS
X EXCESS FUEL BACK
TO TANK
FUEL INLET J9314-170
Fig. 23 Side View—Filter/Regulator—5.9L Engine
LOCKNUT FUEL SUPPLY
TUBE
FUEL FILTER/
FUEL PRESSURE
REGULATOR
PUMP/GAUGE
ELEC. C O N N E C T I O N
PRESSURE RELIEF/ , I I
ROLLOVER VALVE J9314-167
Fig. 24 Filter/Regulator Location—5.9L Engine
is a mechanical device t h a t is not controlled by the
powertrain control module (PCM).
The regulator is calibrated to maintain fuel system
operating pressure at approximately 241-310 k P a
(35-45 psi).
The regulator contains a diaphragm, calibrated
springs and a fuel return valve. The internal fuel fil­
ter (Fig. 23) is part of the assembly.
Fuel is supplied by the electric fuel pump through
an opening tube at the bottom of filter/regulator (Fig.
23). The calibrated pressure regulator allows a con­
stant fuel system operating pressure of approxi­
mately 241-310 kPa (35-45 psi). Fuel flows through
regulator and fuel filter and on to fuel injectors at
engine.
If the fuel pressure at regulator exceeds approxi­
mately 45 psi, an internal diaphragm closes and ex­
cess fuel pressure is routed back into pump module
and returned to fuel t a n k (Fig. 23).