Dodge RAM TRUCK 1500 1995 Service Manual page 1099

BR
FUEL DELIVERY SYSTEM—DIESEL ENGINE 14 - 17
to the engine. Fuel injection occurs near the end of
the compression stroke for each cylinder.
DELIVERY OIL FILL PLUG
VALVES
AFC
AIR FLOW
CONTROL (AFC)
P7100 INLINE
FUEL INJECTION
PUMP
ACCESS
PLUG
J9414-75
Fig. 9 Fuel Injection Pump
The RQV-K governor (Fig. 10) has a pump timing
feature. This will allow the pump shaft to be oriented
in a position corresponding to top dead center (TDC)
for the compression stroke of cylinder number one.
Indexing the governor flyweight assembly to the
shaft during assembly establishes pump timing.
As engine speed increases, the internal pump pres­
sure increases. An air-flow control (AFC) (Fig. 10) on
the governor ensures that regulated fuel delivery is
matched to intake manifold pressure (turbocharger
boost) for emission control.
The mechanical fuel transfer pump delivers fuel
under a low-pressure of approximately 172 Kpa (25
psi) to the injection pump through the fuel filter/wa­
ter separator. The injection pump then supplies high-
pressure fuel of approximately 120,000 kPa (17,400
psi) to each injector in precise metered amounts at
the correct time.
Excess fuel is returned to the fuel tank by an over­
flow valve (Fig. 7) on the injection pump. This vent
opens at approximately 152 kPa (22 psi) and returns
fuel to the fuel tank through the fuel return line.
Diesel fuel and engine oil are used to cool the fuel
injection pump. A separate oil feed line from the en­
gine supplies engine oil to the pump. The oil returns
to the engine through an opening at the front of
pump.
A KSB (cold start) solenoid is not used.
The injection pump high idle speed is factory-
sealed and is not adjustable. The low idle speed is
P7100 INLINE
FUEL INJECTION
PUMP
RQV-K
GOVERNOR
J9414-104
Fig. 10 Injection Pump Governor and AFC
adjustable. Refer to Idle Speed Adjustment in the
Diesel Engine—General Diagnosis section of this
group for procedures.
For diagnosis, refer to the Diesel Engine—General
Diagnosis section of this group.
For removal and installation procedures, refer to
the Diesel Engine—Component Removal/Installation
section of this group.
For injection pump timing, refer to Fuel Injection
Pump Timing in the Diesel Engine — General Diagno­
sis section of this group.
FUEL INJECTORS
The fuel injectors are mounted on the left side of
the cylinder head (Fig. 11). The injectors are con­
nected to the fuel injection pump by the high-pres­
sure fuel lines. A separate injector is used for each
cylinder.
The injectors consist of the nozzle holder, o-ring
water seal, shims, spring, needle valve and nozzle.
Fuel enters the injector at the fuel inlet (top of injec­
tor) and is routed to the needle valve bore. When fuel
pressure rises to approximately 26,252 kPa (3,822
psi), the needle valve spring tension is overcome. The
needle valve rises and fuel flows through the spray
holes in the nozzle tip into the combustion chamber.
The pressure required to lift the needle valve is the
operating pressure setting. This is sometimes re­
ferred to as the "pop" pressure setting.
Fuel pressure in the injector circuit decreases after
injection. The injector needle valve is immediately
closed by the needle valve spring and fuel flow into