Dodge RAM TRUCK 1500 1995 Service Manual page 579

B R
8W-30 FUEL/iGNITiOi—DIESEL ENGINES 8W - 30 - 7
F U E L / I G N I T I O N — D I E S E L E N G I N E S
INDEX
page
Automatic Shut Down (ASD) Relay . 7
Battery Feed 7
Diagram Index 9
Engine Speed Sensor 9
Fuel Heater Relay
8
Fuel Pump Module 7
Fuel Pump Relay . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Fuel Shut Down Relay
8
IGNITION SWITCH
When the ignition switch is in the RUN position, it
connects circuit A2 from fuse 2 in the Power Distri­
bution Center (PDC) to circuit A22. Circuit A22 con­
nects to the fuse block. Through the fuse block,
circuit A22 feeds circuits A20, LIO, F23, CI and F21.
Circuits A20, LIO, F23, and CI are protected by sep­
arate fuses. A circuit breaker protects circuit F21.
When the ignition switch is in the START or RUN
position, it connects circuit Al from fuse 3 in the
PDC to circuit A21. Circuit A21 powers circuits F18,
V34, F12, and F14 through the fuse block. Separate
fuses protect each circuit. In the START position, the
ignition switch connects circuit G9 to ground.
In the ACCESSORY or RUN position, the ignition
switch connects circuit Al to circuit A31. Circuit A31
also connects to the fuse block and feeds circuits F30,
L5, X12, and V6. Separate fuses protect each circuit.
AUTOMATIC SHUT DOWN (ASD) RELAY
Circuit A16 from fuse 4 in the Power Distribution
Center (PDC) supplies battery voltage to the contact
side of the Automatic Shut Down (ASD) relay. Circuit
A16 is HOT at all times.
When the ignition switch is in the START or RUN
position, it connects circuit Al from fuse 3 in the
PDC to circuit A21. Circuit A21 powers circuit F18
through fuse 9 in the fuse block. Circuit F18 supplies
battery voltage to the coil side of the ASD relay. The
Powertrain Control Module (PCM) provides the
ground path for the coil side of the relay on circuit
K51. Circuit K51 connects to cavity 51 of the PCM
connector.
When the PCM provides grounds the ASD relay,
the relay contacts close and connect circuit A16 to
circuit A142. Circuit A142 splices to supply voltage to
the generator field. Circuit A142 also connects to cav­
ity 57 of the PCM.
BATTERY FEED
Circuit A14 from the Power Distribution Center
(PDC) supplies battery voltage to cavity 3 of the Pow-
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Ignition Switch 7
Intake Air Temperature Sensor 9
Intake Manifold Air Heater Relays . . . . . . . . . . . . . .
8
Malfunction Indicator Lamp (MIL) . . . . . . . . . . . . . . . 8
Tachometer 8
Throttle Position Sensor 8
Vehicle Speed Sensor . . . . . . . . . . . . . . . . . . . . . . . 9
Water-ln-Fuel Sensor 9
ertrain Control Module (PCM). A 30 amp fuse in cav­
ity D of the PDC protects circuit A14.
FUEL PUMP RELAY
Circuit A14 from fuse 8 in the Power Distribution
Center (PDC) supplies battery voltage to the contact
side of the fuel pump relay. Circuit F18 from fuse 9
in the fuse block supplies battery voltage to the coil
side of the fuel pump relay. The Powertrain Control
Module (PCM) provides the ground path for the coil
side of the relay on circuit K51. Circuit K51 connects
to cavity 51 of the PCM connector.
When the PCM grounds the fuel pump relay and
the contacts close, they connect circuits A14 and A61.
Circuit A61 supplies power to the fuel pump motor.
HELPFUL INFORMATION
Circuit F18 splices to supply battery voltage to the
coil sides of the ASD relay and fuel pump relay.
FUEL PUMP MODULE .
FUEL PUMP MOTOR
When the fuel pump relay contacts close, circuit
A14 connects to circuit A61. Circuit A61 supplies
voltage to the fuel pump motor. Circuit Z13 provides
ground for the fuel pump motor.
FUEL LEWEL SENSOR
The fuel level sensor is a variable resistor. Circuit
G4 connects the fuel level sensor to the fuel gauge in
the instrument cluster. Circuit F14 from fuse 12 in
the fuse block supplies voltage to the fuel gauge. The
fuel level sensor draws voltage from circuit F14
through the fuel gauge on circuit G4. Circuit Zll pro­
vides the ground path for the fuel level sensor.
As current flows through the coils in the fuel
gauge, it creates a magnetic field. One of the coils in
the gauge receives fixed current. The other coil is
connected to the level sensor. The magnetic field con­
trols the position of the fuel gauge pointer.
The fuel level sensor contains a variable resistor.
As the position of the float arm on the fuel level sen-