1998 DODGE RAM 1500 Intake

INTAKE AIR TEMPERATURE SENSOR (GAS) - BLACK 2 WAY
CAV CIRCUIT FUNCTION
1 K900 18DB/DG SENSOR GROUND
2 K21 18DB/LG IAT SIGNAL
INTAKE AIR TEMPERATURE/MANIFOLD ABSOLUTE PRESSURE SENSOR (DIESEL)-4WAY
CAV CIRCUIT FUNCTION
A K916 18BR/OR SENSOR GROUND
B K21 18DB/LG INTAKE AIR TEMPERATURE SENSOR SIGNAL
C F855 18PK/YL 5 VOLT SUPPLY
D K37 18LB (A/T) BOOST PRESSURE SENSOR SIGNAL
D K37 18BR/OR (M/T) BOOST PRESSURE SENSOR SIGNAL
INTEGRATED POWER MODULE C1 - 26 WAY
CAV CIRCUIT FUNCTION
1 A960 14RD (DIESEL) FUSED B(+)
1 A16 16RD/BR (NGC) FUSED B(+)
2 F21 20PK/DG FUSED IGNITION SWITCH OUTPUT (RUN-START)
3- -
4 F500 20DG/PK FUSED IGNITION SWITCH OUTPUT (RUN)
5 L673 18YL TRAILER TOW LEFT TURN RELAY OUTPUT
6- -
7 L674 18LG TRAILER TOW RIGHT TURN RELAY OUTPUT
8 A981 14RD FUSED B(+)
9 A114 18GY/RD FUSED B(+)
10 L70 18WT/GY FUSED PARK LAMP RELAY OUTPUT
11 F951 16PK/LG FUSED IGNITION SWITCH OUTPUT (RUN-START)
12 A941 18RD FUSED B(+)
13 A919 20RD FUSED B(+)
14 X2 18DG/OR HORN RELAY OUTPUT
15 - -
16 A103 18GY/RD FUSED B(+)
17 L678 18BR PARK LAMP RELAY OUTPUT
18 - -
19 L7 18WT/YL FUSED PARK LAMP RELAY OUTPUT
20 - -
21 - -
22 - -
23 - -
24 - -
25 - -
26 - -
DR8W-80 CONNECTOR PIN-OUTS 8W - 80 - 73

CONNECTOR NAME/NUMBER COLOR LOCATION FIG.
C315 DK GY At Driver Seat N/S
C316 BK At Passenger Seat N/S
C317 BK At Passenger Seat N/S
C319 BK Bottom Left of Left Door N/S
C320 Right Rear Door 43
C322 DK GY Left Rear of Frame 44, 46
C323 BK Left Side of Instrument Panel N/S
C327 BK Right Rear Fender 50, 51
C328 BK Left Rear Fender 50, 51, 52
Camshaft Position Sensor GY Right Front Side of Engine 3, 9
Capacitor Left Rear of Engine Compartment 4
Center High Mounted Stop
Lamp/Cargo LampBK Rear of Cab 49
Cigar Lighter Outlet NAT Rear of Cigar Lighter 32, 35, 36
Clearance Lamp No. 1 BK Left Roof 48
Clearance Lamp No. 2 BK Left-Center Roof 48
Clearance Lamp No. 3 BK Center Roof 48
Clearance Lamp No. 4 BK Right-Center Roof 48
Clearance Lamp No. 5 BK Right Roof 48
Clockspring C1 BK Steering Column 31
Clockspring C2 YL Steering Column 31
Clockspring C3 BK Steering Column N/S
Clockspring C4 BK Steering Column N/S
Clutch Interlock Brake Switch BK At Clutch Pedal 22, 24
Coil On Plug No.1 BK Left Top Side of Intake Manifold 6
Coil On Plug No.2 BK Right Top Side of Intake Manifold 3
Coil On Plug No.3 BK Left Top Side of Intake Manifold 6
Coil On Plug No.4 BK Right Top Side of Intake Manifold 3
Coil On Plug No.5 BK Left Top Side of Intake Manifold 5, 6
Coil On Plug No.6 BK Right Top Side of Intake Manifold 3
Coil On Plug No.7 BK Left Top Side of Intake Manifold 6
Coil On Plug No.8 BK Right Top Side of Intake Manifold 3
Compass/Mini-Trip Computer BK In Overhead Console N/S
Condenser Fan BK Near Condenser 23, 24
Controller Anti-Lock Brake C1 BK Left Fender Side Shield 22, 24, 25
Controller Anti-Lock Brake C2
(ABS)BK Left Fender Side Shield 22, 25
Crankshaft Position Sensor BK Right Rear of Engine Block 3, 9
Cylinder Lock Switch-Driver
(Premium)BK In Left Front Door 41
Cylinder Lock Switch-Passenger
(Premium)LT GY In Right Front Door N/S
Data Link Connector BK Left Bottom of Instrument Panel 35, 38
DR8W-91 CONNECTOR/GROUND/SPLICE LOCATION 8W - 91 - 3
CONNECTOR/GROUND/SPLICE LOCATION (Continued)

CONNECTOR NAME/NUMBER COLOR LOCATION FIG.
Glove Box Lamp and Switch BK At Glove Box 35, 39
Governor Pressure Sensor BK Left Rear of Transmission N/S
Hands Free Module Right Instrument Panel 39
Headlamp Switch BK Left Side of Instrument Panel 32, 35, 38
Headlamp-Left BL At Headlamp 23, 28, 29
Headlamp-Right BL At Headlamp 1, 21, 26
Heated Seat Cushion - Driver BL Under Driver Seat N/S
Heated Seat Cushion - Passenger BL Under Passenger Seat N/S
Heated Seat Switch-Driver RD Center of Instrument Panel 33, 35, 36
Heated Seat Switch-Passenger BL Center of Instrument Panel 33, 35, 36
Horn Switch WT In Steering Wheel N/S
Horn-High Note BK Left Front Fender 23, 28, 29
Horn-Low Note BK Left Front Fender 23, 29
Idle Air Control Motor BK On Throttle Body 6
Ignition Coil GY Left Rear of Engine N/S
Ignition Switch BK Steering Column 31
Inlet Air Temperature/Pressure
SensorBK Right Side Engine 10
Input Speed Sensor BK At Transmission 15, 16
Instrument Cluster C1 GY Rear of Instrument Cluster 35
Instrument Cluster C2 GY Rear of Instrument Cluster 35
Instrument Cluster C3 WT Rear of Instrument Cluster 35
Intake Air Heater Relay Right Engine Compartment 2
Intake Air Temperature/Manifold
Absolute Pressure Sensor (Diesel)BK Left rear Engine N/S
Intake Air Temperature Sensor BK On Intake Manifold 5
Integrated Power Module C1 BK Left Front Fender 26, 28
Integrated Power Module C2 WT Left Front Fender 26, 28
Integrated Power Module C3 GR Left Front Fender 26, 28
Integrated Power Module C4 WT Left Front Fender 26, 28
Integrated Power Module C5 BK Left Front Fender 26, 28
Integrated Power Module C6 BK Left Front Fender 25, 26, 28
Integrated Power Module C7 GY Left Front Fender 26, 28
Integrated Power Module FCM BK In IPM N/S
Knock Sensor BK Left Rear of Engine 5, 7, 9
License Lamp-Left BK At Rear Bumper 50, 51
License Lamp-Right BK At Rear Bumper 50, 51
Lift Pump Motor BK Near T/O for WIF Sensor N/S
Line Pressure Sensor BK Right Rear of Transmission 15, 18
Lumbar Motor-Driver DK GY At Driver Seat N/S
Lumbar Motor-Passenger BK At Passenger Seat N/S
Manifold Absolute Pressure Sensor GY Left Front of Intake Manifold 6
Mode Door Actuator 1 BK Right Side of HVAC N/S
DR8W-91 CONNECTOR/GROUND/SPLICE LOCATION 8W - 91 - 5
CONNECTOR/GROUND/SPLICE LOCATION (Continued)

ENGINE
TABLE OF CONTENTS
page page
ENGINE - 3.7L............................ 1
ENGINE - 4.7L........................... 88ENGINE - 5.7L.......................... 180
ENGINE 5.9L DIESEL..................... 230
ENGINE - 3.7L
TABLE OF CONTENTS
page page
ENGINE - 3.7L
DESCRIPTION..........................3
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - INTRODUCTION............4
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - PERFORMANCE............4
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - MECHANICAL..............6
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - LUBRICATION..............7
DIAGNOSIS AND TESTING - CYLINDER
COMPRESSION PRESSURE..............8
DIAGNOSIS AND TESTING - CYLINDER
COMBUSTION PRESSURE LEAKAGE.......8
STANDARD PROCEDURE
STANDARD PROCEDURE - REPAIR
DAMAGED OR WORN THREADS..........9
STANDARD PROCEDURE - FORM-IN-
PLACE GASKETS AND SEALERS..........9
STANDARD PROCEDURE - ENGINE
GASKET SURFACE PREPARATION........10
REMOVAL.............................10
INSTALLATION.........................11
SPECIFICATIONS
SPECIFICATIONS - 3.7L ENGINE.........12
TORQUE............................16
SPECIAL TOOLS.......................17
AIR CLEANER ELEMENT
REMOVAL.............................21
INSTALLATION.........................21
CYLINDER HEAD - LEFT
DIAGNOSIS AND TESTING - CYLINDER HEAD
GASKET............................21
REMOVAL.............................22
INSTALLATION.........................24
CAMSHAFT(S)
DESCRIPTION.........................25
REMOVAL.............................25INSTALLATION.........................27
CYLINDER HEAD COVER(S)
DESCRIPTION.........................27
REMOVAL.............................28
INSTALLATION.........................28
INTAKE/EXHAUST VALVES & SEATS
DESCRIPTION.........................28
STANDARD PROCEDURE - REFACING......28
REMOVAL.............................29
INSTALLATION.........................30
ROCKER ARM
DESCRIPTION.........................31
REMOVAL.............................31
INSTALLATION.........................31
VALVE GUIDE SEALS
DESCRIPTION.........................32
VALVE SPRINGS
DESCRIPTION.........................32
REMOVAL.............................32
INSTALLATION.........................32
CYLINDER HEAD - RIGHT
DIAGNOSIS AND TESTING - HYDRAULIC
LASH ADJUSTER.....................32
REMOVAL.............................33
INSTALLATION.........................34
CAMSHAFT(S)
DESCRIPTION.........................35
REMOVAL.............................35
INSTALLATION.........................36
CYLINDER HEAD COVER(S)
REMOVAL.............................37
INSTALLATION.........................37
ROCKER ARM
DESCRIPTION.........................37
REMOVAL.............................37
VALVE GUIDE SEALS
DESCRIPTION.........................38
VALVE SPRINGS
DESCRIPTION.........................38
DRENGINE 9 - 1

REMOVAL.............................38
INSTALLATION.........................38
ENGINE BLOCK
DESCRIPTION.........................38
STANDARD PROCEDURE - CYLINDER BORE
HONING............................38
CLEANING............................39
INSPECTION..........................39
CRANKSHAFT
DESCRIPTION.........................40
REMOVAL.............................40
INSPECTION..........................41
INSTALLATION.........................42
CRANKSHAFT MAIN BEARINGS
STANDARD PROCEDURE
MAIN BEARING FITTING................44
CRANKSHAFT OIL SEAL - FRONT
REMOVAL.............................46
INSTALLATION.........................46
CRANKSHAFT OIL SEAL - REAR
REMOVAL.............................47
INSTALLATION.........................47
FLEX PLATE
REMOVAL.............................48
INSTALLATION.........................48
PISTON & CONNECTING ROD
DESCRIPTION.........................48
STANDARD PROCEDURE
CONNECTING ROD BEARING FITTING....49
STANDARD PROCEDURE - PISTON FITTING..51
REMOVAL.............................51
CLEANING............................52
INSPECTION..........................52
INSTALLATION.........................52
PISTON RINGS
STANDARD PROCEDURE - PISTON RING
FITTING.............................53
VIBRATION DAMPER
REMOVAL.............................55
INSTALLATION.........................56
STRUCTURAL COVER
DESCRIPTION.........................57
OPERATION...........................57
REMOVAL.............................57
INSTALLATION.........................57
FRONT MOUNT
REMOVAL.............................58
INSTALLATION.........................59
REAR MOUNT
REMOVAL.............................61
INSTALLATION.........................61
LUBRICATION
DESCRIPTION.........................61
OPERATION...........................61
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE OIL
LEAK...............................64DIAGNOSIS AND TESTING - CHECKING
ENGINE OIL PRESSURE................65
DIAGNOSIS AND TESTING - REAR SEAL
AREA LEAKS.........................65
OIL PAN
DESCRIPTION.........................66
REMOVAL.............................66
CLEANING............................66
INSPECTION..........................66
INSTALLATION.........................66
OIL PRESSURE SENSOR/SWITCH
DESCRIPTION.........................67
OPERATION...........................67
REMOVAL.............................67
INSTALLATION.........................67
OIL PUMP
REMOVAL.............................67
DISASSEMBLY.........................68
INSPECTION..........................68
ASSEMBLY............................69
INSTALLATION.........................69
OIL FILTER
REMOVAL.............................70
INSTALLATION.........................70
OIL
STANDARD PROCEDURE - ENGINE OIL
SERVICE............................71
INTAKE MANIFOLD
DESCRIPTION.........................72
DIAGNOSIS AND TESTING - INTAKE
MANIFOLD LEAKS.....................72
REMOVAL.............................73
INSTALLATION.........................73
EXHAUST MANIFOLD
DESCRIPTION.........................74
REMOVAL.............................74
INSTALLATION.........................74
VALVE TIMING
DESCRIPTION.........................76
OPERATION...........................76
STANDARD PROCEDURE
MEASURING TIMING CHAIN WEAR.......77
SERVICE PROCEDURE - TIMING
VERIFICATION........................77
BALANCE SHAFT
REMOVAL.............................80
INSTALLATION.........................80
IDLER SHAFT
REMOVAL.............................81
INSTALLATION.........................81
TIMING BELT / CHAIN COVER(S)
REMOVAL.............................81
INSTALLATION.........................81
TIMING BELT/CHAIN AND SPROCKETS
REMOVAL.............................83
INSPECTION..........................84
INSTALLATION.........................85
9 - 2 ENGINE - 3.7LDR

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - INTRODUCTION
Engine diagnosis is helpful in determining the
causes of malfunctions not detected and remedied by
routine maintenance.
These malfunctions may be classified as either per-
formance (e.g., engine idles rough and stalls) or
mechanical (e.g., a strange noise).
(Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING) - PERFORMANCE and (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)ÐMECHANICAL for
possible causes and corrections of malfunctions.
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
DIAGNOSIS AND TESTING) and (Refer to 14 -
FUEL SYSTEM/FUEL INJECTION - DIAGNOSIS
AND TESTING) for the fuel system diagnosis.Additional tests and diagnostic procedures may be
necessary for specific engine malfunctions that can
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following diagnosis:
²Cylinder Compression Pressure Test (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
²Cylinder Combustion Pressure Leakage Test
(Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING).
²Engine Cylinder Head Gasket Failure Diagnosis
(Refer to 9 - ENGINE/CYLINDER HEAD - DIAGNO-
SIS AND TESTING).
²Intake Manifold Leakage Diagnosis (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
DIAGNOSIS AND TESTING).
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE
CONDITION POSSIBLE CAUSE CORRECTION
ENGINE WILL NOT START 1. Weak battery 1. Charge or replace as necessary.
2. Corroded or loose battery
connections.2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to the terminals.
3. Faulty starter. 3. (Refer to 8 - ELECTRICAL/
STARTING - DIAGNOSIS AND
TESTING).
4. Faulty coil or control unit. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
5. Incorrect spark plug gap. 5. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
6. Incorrect right bank cam timing. 6. Refer to engine timing in this
section.
7. Dirt or water in fuel system. 7. Clean system and replace fuel
filter.
8.Faulty fuel pump, relay or wiring. 8.Repair or replace as necessary.
9. Faulty cam or crank sensor 9. Refer to Ignition system.
ENGINE STALLS OR ROUGH IDLE 1. Vacuum leak. 1. Inspect intake manifold and
vacuum hoses, repair or replace as
necessary.
2. Faulty crank position sensor 2. Replace crank position sensor.
3. Faulty coil. 3. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
9 - 4 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - MECHANICAL
CONDITION POSSIBLE CAUSES CORRECTIONS
NOISY VALVES 1. High or low oil level in
crankcase.1. (Refer to LUBRICATION &
MAINTENANCE -
SPECIFICATIONS)
2. Thin or diluted oil. 2. Change oil and filter.
3. Low oil pressure. 3. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.
4. Dirt in lash adjusters. 4. Replace as necessary.
5. Worn rocker arms. 5. Replace as necessary.
6. Worn lash adjusters 6. Replace as necessary.
7. Worn valve guides. 7. (Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES
& SEATS - STANDARD
PROCEDURE)
8. Excessive runout of valve seats
on valve faces.8. (Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES
& SEATS - STANDARD
PROCEDURE)
CONNECTING ROD NOISE 1. Insufficient oil supply. 1. (Refer to LUBRICATION &
MAINTENANCE -
SPECIFICATIONS)
2. Low oil pressure. 2. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.
3. Thin or diluted oil. 3. Change oil and filter.
4. Excessive bearing clearance. 4. Replace as necessary.
5. Connecting rod journal
out-of-round.5. Service or replace crankshaft.
6. Misaligned connecting rods. 6. Replace bent connecting rods.
MAIN BEARING NOISE 1. Insufficient oil supply. 1. (Refer to LUBRICATION &
MAINTENANCE -
SPECIFICATIONS)
2. Low oil pressure. 2. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.
3. Thin or diluted oil. 3. Change oil and filter.
4. Excessive bearing clearance. 4. Replace as necessary.
5. Excessive end play. 5. Check thrust washers for wear.
6. Crankshaft journal out-of round. 6. Service or replace crankshaft.
7. Loose flywheel or torque
converter.7. Tighten to correct torque
9 - 6 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
OIL PUMPING AT RINGS; SPARK
PLUGS FOULING1. Worn or damaged rings. 1. Hone cylinder bores and replace
rings.
2. Carbon in oil ring slots. 2. Replace rings (Refer to 9 -
ENGINE/ENGINE BLOCK/PISTON
RINGS - STANDARD
PROCEDURE).
3. Incorrect ring size installed. 3. Replace rings (Refer to 9 -
ENGINE/ENGINE BLOCK/PISTON
RINGS - STANDARD
PROCEDURE).
4. Worn valve guides. 4. Ream guides and replace valves
(Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES
& SEATS - STANDARD
PROCEDURE).
5. Leaking valve guide seals. 5. Replace valve guide seals.
DIAGNOSIS AND TESTING - CYLINDER
COMPRESSION PRESSURE
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Clean the spark plug recesses with compressed
air.
(2) Remove the spark plugs.
(3) Disable the fuel system (Refer to 14 - FUEL
SYSTEM/FUEL DELIVERY - DESCRIPTION).
(4) Remove the ASD relay (Refer to 8 - ELECTRI-
CAL/IGNITION CONTROL/AUTO SHUT DOWN
RELAY - REMOVAL).
(5) Insert a compression pressure gauge and rotate
the engine with the engine starter motor for three
revolutions.
(6) Record the compression pressure on the 3rd
revolution. Continue the test for the remaining cylin-
ders.
(7) (Refer to 9 - ENGINE - SPECIFICATIONS) for
the correct engine compression pressures.
DIAGNOSIS AND TESTING - CYLINDER
COMBUSTION PRESSURE LEAKAGE
The combustion pressure leakage test provides an
accurate means for determining engine condition.
Combustion pressure leakage testing will detect:
²Exhaust and intake valve leaks (improper seat-
ing).²Leaks between adjacent cylinders or into water
jacket.
²Any causes for combustion/compression pressure
loss.
(1) Check the coolant level and fill as required. DO
NOT install the radiator cap.
(2) Start and operate the engine until it attains
normal operating temperature, then turn the engine
OFF.
(3) Remove the spark plugs.
(4) Remove the oil filler cap.
(5) Remove the air cleaner hose.
(6) Calibrate the tester according to the manufac-
turer's instructions. The shop air source for testing
should maintain 483 kPa (70 psi) minimum, 1,379
kPa (200 psi) maximum and 552 kPa (80 psi) recom-
mended.
(7) Perform the test procedures on each cylinder
according to the tester manufacturer's instructions.
Set piston of cylinder to be tested at TDC compres-
sion,While testing, listen for pressurized air escaping
through the throttle body, tailpipe and oil filler cap
opening. Check for bubbles in the radiator coolant.
All gauge pressure indications should be equal,
with no more than 25% leakage.
FOR EXAMPLE:At 552 kPa (80 psi) input pres-
sure, a minimum of 414 kPa (60 psi) should be main-
tained in the cylinder.
Refer to CYLINDER COMBUSTION PRESSURE
LEAKAGE DIAGNOSIS CHART.
9 - 8 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)