1998 DODGE RAM 1500 ecm

(11) Before starting engine, operate accelerator
pedal to check for any binding.
SWITCH
DESCRIPTION
Two separate switch pods operate the speed control
system. The steering-wheel-mounted switches use
multiplexed circuits to provide inputs to the PCM (to
the ECM for diesel) for ON, OFF, RESUME, ACCEL-
ERATE, SET, DECEL and CANCEL modes. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures.
The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
Depending on engine control computer (JTEC
having a 3± plug connector or NGC having a 4±
plug connector), 2 types of switches are used.
Both types of switches are internally and exter-
nally different. The switch used with the NGC
system has an attached pigtail lead. The switch
used with the JTEC system does not have an
attached pigtail lead.
OPERATION
When speed control is selected by depressing the
ON, OFF switch, the PCM(ECM for diesel)allows
a set speed to be stored in its RAM for speed control.
To store a set speed, depress the SET switch while
the vehicle is moving at a speed between approxi-
mately 35 and 85 mph. In order for the speed control
to engage, the brakes cannot be applied, nor can the
gear selector be indicating the transmission is in
Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
²Depressing the OFF switch
²Depressing the CANCEL switch.
The speed control can be disengaged also by any of
the following conditions:
²An indication of Park or Neutral (auto. trans.)
²The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
²Depressing the clutch pedal (manual trans.).
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
²If the actual speed is not within 20 mph of the
set speed
Fig. 6 SPEED CONTROL SERVO LOCATION
1 - BATTERY TRAY
2 - MOUNTING LUGS
3 - SERVO
4 - ELEC. CONNEC.
5 - MOUNTING SCREWS (3)
6 - MOUNTING BRACKET
7 - VACUUM LINE
Fig. 7 SERVO CABLE CLIP REMOVE/INSTALL Ð
TYPICAL
1 - SERVO MOUNTING NUTS (2)
2 - SERVO
3 - CABLE RETAINING CLIP
4 - SERVO CABLE AND SLEEVE
DRSPEED CONTROL 8P - 7
SERVO (Continued)

The previous disengagement conditions are pro-
grammed for added safety.
Once the speed control has been disengaged,
depressing the ACCEL switch restores the vehicle to
the target speed that was stored in the PCM's RAM
(ECM for diesel).
NOTE: Depressing the OFF switch will erase the set
speed stored in the PCM's/ECM's RAM.
If, while the speed control is engaged, the driver
wishes to increase vehicle speed, the PCM(ECM for
diesel)is programmed for an acceleration feature.
With the ACCEL switch held closed, the vehicle
accelerates slowly to the desired speed. The new tar-
get speed is stored in the PCM's/ECM's RAM when
the ACCEL switch is released. The PCM/ECM also
has a9tap-up9feature in which vehicle speed
increases at a rate of approximately 2 mph for each
momentary switch activation of the ACCEL switch.
The PCM/ECM also provides a means to decelerate
without disengaging speed control. To decelerate from
an existing recorded target speed, depress and hold
the COAST switch until the desired speed is reached.
Then release the switch. The ON, OFF switch oper-
ates two components: the PCM's/ECM's ON, OFF
input, and the battery voltage to the brake switch.
REMOVAL
Depending on engine control computer (JTEC
having a 3±plug connector or 5.7L V-8 NGC hav-
ing a 4±plug connector), 2 types of switches are
used. Both types of switches are internally and
externally different. The switches used with the
NGC system have attached pigtail leads (Fig. 9).
The switch used with the JTEC system does not
have an attached pigtail lead.
(1) Remove switch mounting screw (Fig. 8). or
(Fig. 9)
(2) Pull switch from steering wheel.
(3) Unplug electrical connector from switch (Fig.
8), or, switch pigtail wire harness from steering
wheel wire harness (Fig. 9) and remove switch.
INSTALLATION
(1) Plug electrical connector into switch (Fig. 8), or
connect pigtail wire harness to steering wheel wire
harness (Fig. 9). Be sure wires are not pinched.
(2) Position switch to steering wheel.
(3) Install switch mounting screw and tighten.
Refer to torque specifications.
Fig. 8 SPEED CONTROL SWITCHES (EXCEPT 5.7L
V-8 ENGINE)
1 - ELECTRICAL CONNECTORS
2 - MOUNTING SCREWS
3 - RIGHT SWITCH
4 - LEFT SWITCH
Fig. 9 SPEED CONTROL SWITCHES (WITH 5.7L V-8
ENGINE)
1 - MOUNTING SCREWS
2 - RIGHT SWITCH
3 - LEFT SWITCH
4 - PIGTAIL LEADS
8P - 8 SPEED CONTROLDR
SWITCH (Continued)

DIAGNOSIS AND TESTINGÐSMOKE DIAGNOSIS CHARTS
The following charts include possible causes and cor-
rections forexcess or abnormalexhaust smoke. Smallamounts of exhaust smoke (at certain times) are to be
considered normal for a diesel powered engine.
EXCESSIVE BLACK SMOKE
POSSIBLE CAUSE CORRECTION
Air filter dirty or plugged. Check Filter MinderTat air filter (Refer to 9 - ENGINE/
AIR INTAKE SYSTEM/AIR CLEANER ELEMENT -
REMOVAL).
Air intake system restricted. Check entire air intake system including all hoses and
tubes for restrictions, collapsed parts or damage.
Repair/replace as necessary.
Air Leak in Intake System. Check entire air intake system including all hoses and
tubes for cracks, loose clamps and/or holes in rubber
ducts. Also check intake manifold for loose mounting
hardware.
Diagnostic Trouble Codes (DTC's) active or multiple,
intermittent DTC's.Refer to Powertrain Diagnostic Procedures Information.
Engine Control Module (ECM) not calibrated or ECM
has incorrect calibration.Refer to Powertrain Diagnostic Procedures Information.
Exhaust system restriction is above specifications. Check exhaust pipes for damage/restrictions. Repair as
necessary.
Fuel grade is not correct or fuel quality is poor. Temporarily change fuel brands and note condition.
Change brand if necessary.
Fuel injection pump malfunctioning. A DTC may have been set. If so, refer to Powertrain
Diagnostic Procedures Information.
Fuel injector malfunctioning. A DTC may have been set. Perform9Cylinder Cutout
Test9using DRB scan tool to isolate individual
cylinders. Also refer to Powertrain Diagnostic
Procedures Information and, to (Refer to 14 - FUEL
SYSTEM/FUEL INJECTION/FUEL INJECTOR -
DIAGNOSIS AND TESTING).
Fuel return system restricted. Check fuel return lines for restriction (Refer to 14 -
FUEL SYSTEM/FUEL DELIVERY - DIAGNOSIS AND
TESTING).
Intake manifold restricted. Remove restriction.
Manifold Air Pressure (Boost) Sensor or sensor circuit
malfunctioning.A DTC should have been set. Refer to Powertrain
Diagnostic Procedures Information.
Raw fuel in intake manifold. Fuel injectors leaking on engine shutdown. Do Fuel
Injector Test (Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/FUEL INJECTOR - DIAGNOSIS AND
TESTING).
Turbocharger air intake restriction. Remove restriction.
Turbocharger damaged. (Refer to 11 - EXHAUST SYSTEM/TURBOCHARGER
SYSTEM/TURBOCHARGER - INSPECTION).
Turbocharger has excess build up on compressor
wheel and/or diffuser vanes.(Refer to 11 - EXHAUST SYSTEM/TURBOCHARGER
SYSTEM/TURBOCHARGER - CLEANING).
Turbocharger wheel clearance out of specification. (Refer to 11 - EXHAUST SYSTEM/TURBOCHARGER
SYSTEM/TURBOCHARGER - INSPECTION).
9 - 236 ENGINE 5.9L DIESELDR
ENGINE 5.9L DIESEL (Continued)

EXCESSIVE WHITE SMOKE
POSSIBLE CAUSE CORRECTION
Air in fuel supply: Possible leak in fuel supply side (between
transfer pump and fuel tank module).(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY/FUEL
TRANSFER PUMP - DIAGNOSIS AND TESTING).
Coolant leaking into combustion chamber. Do pressure test of cooling system (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
Diagnostic Trouble Codes (DTC's) active or multiple,
intermittent DTC's.Refer to Powertrain Diagnostic Procedures Information.
In very cold ambient temperatures, engine block heater is
malfunctioning (if equipped).(Refer to 7 - COOLING/ENGINE/ENGINE BLOCK HEATER -
REMOVAL).
Engine coolant temperature sensor malfunctioning. A DTC should have been set. Refer to Powertrain Diagnostic
Procedures Information. Also check thermostat operation
(Refer to 7 - COOLING/ENGINE/ENGINE COOLANT
THERMOSTAT - DIAGNOSIS AND TESTING).
Engine Control Module (ECM) not calibrated or has incorrect
calibration.A DTC should have been set. Refer to Powertrain Diagnostic
Procedures Information.
Fuel filter plugged. Refer to Powertrain Diagnostic Manual for fuel system testing.
Fuel grade not correct or fuel quality is poor. Temporarily change fuel brands and note condition. Change
brand if necessary.
Fuel heater element or fuel heater temperature sensor
malfunctioning. This will cause wax type build-up in fuel filter.Refer to Fuel Heater Testing (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY/FUEL HEATER - DIAGNOSIS AND
TESTING).
Fuel injector malfunctioning. A DTC should have been set. Perform9Cylinder cutout Test9
using DRB scan tool to isolate individual cylinders. Also refer
to Powertrain Diagnostic Procedures Information and, (Refer
to 14 - FUEL SYSTEM/FUEL INJECTION/FUEL INJECTOR -
DIAGNOSIS AND TESTING).
Fuel injector hold-downs loose. Torque to specifications.
Fuel injector protrusion not correct. Check washer (shim) at bottom of fuel injector for correct
thickness. (Refer to 14 - FUEL SYSTEM/FUEL INJECTION/
FUEL INJECTOR - INSTALLATION)
Fuel injection pump malfunctioning. A DTC should have been set. Refer to Powertrain Diagnostic
Procedures Information.
Fuel supply side restriction to transfer pump. Refer to Powertrain Diagnostic Manual for fuel system testing.
Fuel transfer (lift) pump malfunctioning. A DTC may have been set. Refer to Powertrain Diagnostic
Procedures Information.
Intake/Exhaust valve adjustments not correct (too tight). (Refer to 9 - ENGINE/CYLINDER HEAD/INTAKE/EXHAUST
VALVES & SEATS - STANDARD PROCEDURE).
Intake manifold air temperature sensor malfunctioning. A DTC should have been set. Refer to Powertrain Diagnostic
Procedures Information.
Intake manifold heater circuit not functioning correctly in cold
weather.A DTC should have been set. Refer to Powertrain Diagnostic
Procedures Information. Also check heater elements for
correct operation.
Intake manifold heater elements not functioning correctly in
cold weather.A DTC should have been set if heater elements are
malfunctioning. Refer to Powertrain Diagnostic Procedures
Information.
Internal engine damage (scuffed cylinder). Analyze engine oil and inspect oil filter to locate area of
probable damage.
Restriction in fuel supply side of fuel system. Refer to Powertrain Diagnostic Manual for fuel system testing.
DRENGINE 5.9L DIESEL 9 - 237
ENGINE 5.9L DIESEL (Continued)

(10) Drain engine oil. Remove and discard the oil
filter (Refer to 9 - ENGINE/LUBRICATION/OIL FIL-
TER - REMOVAL).
(11) Install the drain plug. Tighten the plug to 50
N´m (37 ft. lbs.) torque.
(12) Install a new oil filter (Refer to 9 - ENGINE/
LUBRICATION/OIL FILTER - INSTALLATION).
(13) Fill engine crankcase with the specified
amount and grade of oil (Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES - SPECIFICA-
TIONS).
(14) Connect the negative cable(s) to the battery.
(15) Start the engine and check for any leaks.
REMOVAL
REMOVAL - ENGINE
(1) Disconnect both battery negative cables.
(2) Disconnect engine grid heater harness at grid
heater relays.
(3) Disconnect electrical connections from rear of
alternator.
(4) Recover A/C refrigerant. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE).
(5) Raise vehicle on a hoist.
(6) Drain engine coolant (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(7) Remove engine oil drain plug and drain engine
oil.
(8) Reinstall drain plug. Tighten to 50N´m (37 ft.
lbs.) torque.
(9) Lower the vehicle.
(10) Remove fan/drive assembly. Refer to Section 7
± Fan/Drive Removal
(11) Remove radiator upper hose.
(12) Remove upper fan shroud mounting bolts.
(13) Disconnect the coolant recovery bottle hose
from the radiator fill neck and remove bottle.
(14) Using a 36mm wrench, remove viscous fan/
drive assembly. (Refer to 7 - COOLING/ENGINE/RA-
DIATOR FAN - REMOVAL).
(15) Remove cooling fan and shroud together.
(16) Disconnect heater core supply and return
hoses from the cylinder head fitting and coolant pipe.
(17) Raise vehicle on a hoist.
(18) Remove transmission and transfer case (if
equipped).
(19) Disconnect exhaust pipe from turbocharger
extension pipe.
(20) Disconnect engine harness to vehicle harness
connectors.
(21) Remove starter motor (Refer to 8 - ELECTRI-
CAL/STARTING/STARTER MOTOR - REMOVAL).(22) Remove flywheel/flexplate.
(23) Remove transmission adapter
(24) Disconnect A/C suction/discharge hose from
the rear of the A/C compressor.
(25) Lower vehicle.
(26) Disconnect lower radiator hose from radiator
outlet.
(27) Automatic transmission models:
(28) Disconnect transmission oil cooler lines from
in front of radiator using special tool #6931
(29) Remove radiator. (Refer to 7 - COOLING/EN-
GINE/RADIATOR - REMOVAL).
(30) If A/C equipped, disconnect A/C condenser
refrigerant lines.
(31) Disconnect charge air cooler piping.
(32) Remove charge air cooler mounting bolts.
(33) Remove charge air cooler (and A/C condenser
if equipped) from vehicle.
(34) Remove damper and speed indicator ring from
front of engine.
(35) Disconnect engine block heater connector.
(36) Disconnect A/C compressor and pressure sen-
sor electrical connectors.
(37) Remove the passenger battery ground cable
from the engine block. Remove the driver side bat-
tery ground cable from the engine block.
(38) Remove power steering pump from engine by
removing 3 bolts.
(39) Remove accelerator linkage cover.
(40) Disconnect cables from on-engine APPS.
(41) Disconnect the ECM power connector.
(42) Disconnect the ECM ground wire from the
hydroform screw.
(43) Disconnect the fuel supply and return hoses.
(44) Remove the cylinder head cover. (Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - REMOVAL).
(45) Disconnect the 3 injector harness connectors
at the rocker housing. Disconnect the wire harnesses
from the injectors.
(46) Remove the rear engine lift bracket.
(47) Remove cylinder #4, #5, and #6 intake and
exhaust rocker arms, pedestals, and push tubes. Note
the original location for re-assembly.
(48) Loosen #6 fuel line shield bolts and rotate
shield out of the way.
(49) Remove cylinder #5 and #6 high pressure fuel
lines. Remove the fuel connector tube nut and fuel
connector tube. Remove cylinder #5 and #6 fuel injec-
tor.
(50) Remove rocker housing.
DRENGINE 5.9L DIESEL 9 - 241
ENGINE 5.9L DIESEL (Continued)

(8) Replace injector o-ring and sealing washer on
injectors #5 and #6. Install injectors and torque using
the following steps:
²Step 1ÐInstall injector hold-down capscrews
and torque to 5 N´m (44 in. lbs.) torque.
²Step 2ÐLoosen injector hold-down capscrews.
²Step 3ÐInstall HPC connector tube and nut.
Torque nut to 15 N´m (11 ft. lbs.) torque.
²Step 4ÐTorque injector hold-down capscrews to
10 N´m (89 in. lbs.) torque.
²Step 5ÐTorque HPC connector tube nut to 50
N´m (37 ft. lbs.) torque.
(9) Install #5 and #6 high pressure fuel lines. Fol-
low correct torque sequence per section 14. Torque
fuel line fittings to 30 N-m (22 ft-lb). Torque brace
capscrew to 24 N-m (18 ft-lb).
(10) Install rear engine lift bracket. Torque to 77
N-m (57 ft-lb).
(11) Install push tubes, rocker arms, and pedestals
for cylinders #4, #5, and #6. Torque the mounting
bolts to 36 N-m (27 ft-lbs).
(12) Reset valve lash on cylinders #4, #5, and #6.
Torque adjusting nuts to 24 N-m (18 ft-lbs).
(13) Install cylinder head cover. Torque to 24 N-m
(18 ft-lbs).(Refer to 9 - ENGINE/CYLINDER HEAD -
INSTALLATION).
(14) Connect breather tube and lube oil drain tube
to breather housing cover. Install breather housing.
Torque capscrews to 24 N-m (18 ft-lbs)
(15) Connect fuel supply and return hoses.
(16) Connect ECM ground to hydroform screw.
Connect ECM power connector.
(17) Install the APPS cable(s) to the APPS. Install
the throttle linkage cover.
(18) Install the power steering pump.
(19) Install the damper and speed indicator ring.
Torque to 40 N-m (30 ft-lb) plus 60 degrees.
(20) Connect the engine block heater connection.
(21) Connect the A/C compressor and pressure sen-
sor connectors
(22) Install the charge air cooler and a/c condenser
(if equipped). Install and tighten the charge air
cooler mounting bolts to 2 N-m (17 in-lbs).
(23) Connect the charge air cooler piping. Torque
all clamps to 8 N-m (72 in-lbs).
(24) Connect the a/c refrigerant lines to the a/c
condenser (if equipped).
(25) Install the radiator upper support panel.
(26) Install radiator.
(27) Connect the transmission quick-connect oil
cooler lines.(28) Raise vehicle.
(29) Connect a/c compressor suction/discharge hose
(if equipped).
(30) Install the radiator lower hose and clamps.
(31) Install the battery negative cables to the
engine block on the driver and passenger side.
(32) Install the transmission adapter with a new
camshaft rectangular ring seal. Torque to 77 N-m (57
ft-lb).
(33) Install the flywheel/flexplate. Torque to 137
N-m (101 ft-lb).
(34) Install the starter motor. Torque to 43 N-m
(32 ft-lb). (Refer to 8 - ELECTRICAL/STARTING/
STARTER MOTOR - INSTALLATION).
(35) Connect engine to vehicle harness connectors.
(36) Install transmission and transfer case (if
equipped).
(37) Connect the exhaust pipe to the turbocharger
elbow.
(38) Connect the transmission auxiliary oil cooler
lines (if equipped).
(39) Lower the vehicle.
(40) Connect the heater core supply and return
hoses.
(41) Install the cooling fan and upper fan shroud
at the same time. (Refer to 7 - COOLING/ENGINE/
RADIATOR FAN - INSTALLATION).
(42) Install the coolant recovery bottle.
(43) Install the windshield washer bottle.
(44) Install the upper radiator hose and clamps.
(45) Raise vehicle.
(46) Connect electronically controlled fan drive
wire harness. Install lower radiator fan shroud.
(47) Change oil filter and install new engine oil.
(48) Fill the cooling system with coolant. (Refer to
7 - COOLING - STANDARD PROCEDURE).
(49) Connect grid heater harness at grid heater
relays.
(50) Connect electrical connections to rear of alter-
nator.
(51) Start the engine and inspect for engine oil,
coolant, and fuel leaks.
INSTALLATIONÐCRANKCASE BREATHER
(1) Install a new o-ring onto the breather element.
(2) Lubricate o-ring and install into cylinder head
cover. Torque capscrews to 10 N´m (89 in. lbs.).
(3) Connect breather tube and lube oil drain tube.
(4) Install breather cover (Fig. 4). Torque to 24
N´m (18 ft. lbs.)
(5) Install oil fill cap.
DRENGINE 5.9L DIESEL 9 - 243
ENGINE 5.9L DIESEL (Continued)

INSTALLATION
Threads of new oxygen sensors are factory coated
with anti-seize compound to aid in removal.DO
NOT add any additional anti-seize compound to
threads of a new oxygen sensor.
(1) Install O2S sensor. Tighten to 30 N´m (22 ft.
lbs.) torque.
(2) Connect O2S sensor wire connector.
(3) Lower vehicle.
PTO SWITCH
DESCRIPTION
This Powertrain Control Module (PCM) input is
used only on models equipped with aftermarket
Power Take Off (PTO) units.
OPERATION
The input is used only to tell the PCM (or ECM-
Diesel) that the PTO has been engaged. The PCM (or
ECM) will disable (temporarily shut down) certain
OBD II diagnostic trouble codes when the PTO is
engaged.
JTEC and NGC Engine Controllers:When the
aftermarket PTO switch has been engaged, a 12V +
signal is sent through circuit G113 to PCM pin A13.
The PCM will then sense and determine that the
PTO has been activated.
CM 845 or CM 848 Diesel Engine Controllers:
When the aftermarket PTO switch has been engaged,
a 12V + signal is sent through circuit G113 to ECM
pin B38. The ECM will then sense and determine
that the PTO has been activated.
THROTTLE BODY
DESCRIPTION
The throttle body is located on the intake manifold.
Fuel does not enter the intake manifold through the
throttle body. Fuel is sprayed into the manifold by
the fuel injectors.
OPERATION
Filtered air from the air cleaner enters the intake
manifold through the throttle body. The throttle body
contains an air control passage controlled by an Idle
Air Control (IAC) motor. The air control passage is
used to supply air for idle conditions. A throttle valve
(plate) is used to supply air for above idle conditions.
5.7L V-8 Engine:
The throttle body on the 5.7L engine is an electri-
cally controlled unit. A mechanical cable is not used
to connect the throttle body to the accelerator pedal.
The Accelerator Pedal Position Sensor (APPS) alongwith inputs from other sensors sets the throttle blade
to pre-determined positions.
Except 5.7L V-8 Engine:
Certain sensors are attached to the throttle body.
The accelerator pedal cable, speed control cable and
transmission control cable (when equipped) are con-
nected to the throttle body linkage arm.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the PCM.
REMOVAL
3.7L V-6
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the Powertrain Control Module (PCM).
(1) Remove air cleaner tube at throttle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS.
(3) Remove all control cables from throttle body
(lever) arm. Refer to the Accelerator Pedal and Throt-
tle Cable section for removal/installation procedures.
(4) Disconnect necessary vacuum lines at throttle
body.
(5) Remove 3 throttle body mounting bolts (Fig.
28).
(6) Remove throttle body from intake manifold.
(7) Check condition of old throttle body-to-intake
manifold o-ring (Fig. 29).
4.7L V-8
(1) Remove air duct and air resonator box at throt-
tle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS (Fig. 30).
(3) Remove vacuum line at throttle body.
(4) Remove all control cables from throttle body
(lever) arm. Refer to Accelerator Pedal and Throttle
Cable.
(5) Remove three throttle body mounting bolts
(Fig. 30).
(6) Remove throttle body from intake manifold.
5.7L V-8
CAUTION: Do not use spray (carb) cleaners on any
part of the throttle body. Do not apply silicone lubri-
cants to any part of the throttle body.
(1) Remove air duct and air resonator box at throt-
tle body.
14 - 36 FUEL INJECTION - GASDR
OXYGEN SENSOR (Continued)

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:
²Electric Fuel Transfer (lift) Pump
²Fuel Pump/Gear Pump (attached to fuel injec-
tion pump)
²High-Pressure Fuel Injection Pump
²Fuel Injection Rail
²Fuel Injectors
Also to be considered as part of the overall fuel
system are:
²Accelerator Pedal
²Air Cleaner Housing/Element
²Fuel Drain Manifold (passage)
²Fuel Drain Valve (at filter)
²Fuel Filter/Water Separator
²Fuel Heater
²Fuel Heater Relay
²Fuel Level (gauge) Sending Unit
²Fuel Pressure Limiting Valve
²Fuel Tank
²Fuel Tank Module (containing fuel gauge send-
ing unit and separate fuel filter located at bottom of
tank module)
²Fuel Tank Filler/Vent Tube Assembly
²Fuel Tank Filler Tube Cap
²Fuel Tubes/Lines/Hoses
²High-Pressure Fuel Injector Lines
²In-Tank Fuel Filter (at bottom of fuel tank mod-
ule)
²Low-Pressure Fuel Supply Lines
²Low-Pressure Fuel Return Line
²Overflow Valve
²Quick-Connect Fuel Line Fittings
²Throttle Cable
²Water Draining (maintenance)
²Water-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 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).
DRFUEL DELIVERY - DIESEL 14 - 45