Dodge ram truck 3500 1996 Service Manual page 1308

14 - 74 FUEL SYSTEM
B R
D E S C R I P T I O N AMD OPERATION (Continued)
WARNING: USE EXTREME CAUTION WHEN
INSPECTING FOR HIGH-PRESSURE FUEL LEAKS.
INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH
A SHEET OF CARDBOARD. HIGH FUEL INJECTION
PRESSURE CAN CAUSE PERSONAL INJURY IF
CONTACT IS MADE WITH THE SKIN.
FUEL INJECTION PUMP
The fuel injection pump is a Bosch
P 7 1 0 0
series in­
line type (Fig. 9). The injection pump is driven by the
engine camshaft. A gear on the end of the pump shaft
meshes with the camshaft gear. The pump is timed
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. 9 ) 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-fuel 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.
P7100 INLINE
FUEL INJECTION
PUMP
RQV-K
GOVERNOR
J9414-104
Fig. 10 Injection Pump Governor and AFC
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
engine 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
adjustable. Refer to Idle Speed Adjustment.
For injection pump timing, refer to Fuel Injection
Pump Timing.
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
referred to as the "pop" pressure setting.