Dodge RAM 1500 1998 Owner's Manual page 1614

DR
FUEL DELIVERY - DIESEL
DESCRIPTION - DIESEL FUEL SYSTEM
The fuel system used on the Cummins engine is an
electronically controlled, Bosch HPCR (High-Pressure
Common Rail) system. The HPCR system consists of
five main components:
• Electric Fuel Transfer (lift) Pump
• Fuel Pump/Gear Pump (attached to fuel injec-
tion pump)
• High-Pressure Fuel Injection Pump
• Fuel Injection Rail
• Fuel Injectors
Also to be considered as part of the overall fuel
system are:
• Accelerator Pedal
• Air Cleaner Housing/Element
• Fuel Drain Manifold (passage)
• Fuel Drain Valve (at filter)
• Fuel Filter/Water Separator
• Fuel Heater
• Fuel Heater Relay
• Fuel Level (gauge) Sending Unit
• Fuel Pressure Limiting Valve
• Fuel Tank
• Fuel Tank Module (containing fuel gauge send-
ing unit and separate fuel filter located at bottom of
tank module)
• Fuel Tank Filler/Vent Tube Assembly
• Fuel Tank Filler Tube Cap
• Fuel Tubes/Lines/Hoses
• High-Pressure Fuel Injector Lines
• In-Tank Fuel Filter (at bottom of fuel tank mod-
ule)
• Low-Pressure Fuel Supply Lines
• Low-Pressure Fuel Return Line
• Overflow Valve
• Quick-Connect Fuel Line Fittings
• Throttle Cable
• Water Draining (maintenance)
• Water-In-Fuel (WIF) Sensor
The fuel injection pump supplies high pressure to
the fuel rail independent of engine speed. This high
pressure fuel is then accumulated in the fuel rail.
High pressure fuel is constantly supplied to the injec-
tors by the fuel rail. The Engine Control Module
(ECM) controls the fueling and timing of the engine
by actuating the injectors.
FUEL DELIVERY - DIESEL
Fuel enters the system from the electric fuel trans-
fer (lift) pump, which is attached to the fuel filter
assembly. Fuel is forced through the fuel filter ele-
ment and then enters the Fuel Pump/Gear Pump,
which is attached to the rear of the fuel injection
pump. The Fuel Pump/Gear Pump is a low-pressure
pump and produce pressures ranging from 551.5 kpa
(80 psi) to 1241 kpa (180) psi. Fuel then enters the
fuel injection pump. Low pressure fuel is then sup-
plied to the FCA (Fuel Control Actuator).
The FCA is an electronically controlled solenoid
valve. The ECM controls the amount of fuel that
enters the high-pressure pumping chambers by open-
ing and closing the FCA based on a demanded fuel
pressure. The FPS (Fuel Pressure Sensor) on the fuel
rail monitors the actual fuel pressure and provides it
as an input to the ECM. When the actuator is
opened, the maximum amount of fuel is being sup-
plied to the fuel injection pump. Any fuel that does
not enter the injection pump is directed to the over-
flow valve. The overflow valve regulates how much
excess fuel is used for lubrication of the pump and
how much is returned to the tank through the drain
manifold.
Fuel entering the injection pump is pressurized to
between 300-1600 bar (4351-23,206 psi) by three
radial pumping chambers. The pressurized fuel is
then supplied to the fuel rail.
WARNING: HIGH-PRESSURE FUEL LINES DELIVER
DIESEL FUEL UNDER EXTREME PRESSURE FROM
THE INJECTION PUMP TO THE FUEL INJECTORS.
THIS MAY BE AS HIGH AS 160,000 KPA (23,206
PSI). 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.
Certain fuel system components can be found in
(Fig. 1), or (Fig. 2).
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