Dodge ram truck 3500 1996 Service Manual page 1309

BR
FUEL SYSTEM 14 - 75
VTION f C o n t i n u e d !
HIGH
PRESSURE
FUEL LINE
6 )
FRONT OF ENGINE
AIR TEMPERATURE
SENSOR
J91l 4-74 ^
Fig. 11 Fuel Injectors—Typical
Fuel pressure in the injector circuit decreases after
injection. The injector needle valve is immediately
closed by the needle valve spring and fuel flow into
the combustion chamber is stopped. Exhaust gases
are prevented from entering the injector nozzle by
the needle valve.
FUEL SHUTDOWN SOLENOID
The fuel shutdown solenoid and fuel shut­
down solenoid relay are not controlled by the
powertrain control module (PCM).
The fuel shutdown (shut-off) solenoid is used to
electrically shut off the diesel fuel supply to the high-
pressure fuel injection pump. The solenoid is
mounted to the side of the pump and is connected to
the pump with a lever (Fig. 12).
The solenoid controls starting and stopping of the
engine regardless of the position of the accelerator
pedal. When the ignition switch is off, the solenoid
plunger is spring loaded (down) in the shutdown posi­
tion (Fig. 13) and fuel is shut off to the injection pump.
Two different coils are located within the solenoid
and a three-wire pigtail wire harness is attached to
the solenoid.
When the ignition switch is turned to the CRANK
(starter engaged) position, high-amperage current
(approximately 40 amps at 12 volts) is supplied to
one of the coils in the shutdown solenoid from the
fuel shutdown solenoid relay. This high-amperage
current allows the solenoid shaft to pull up on the
injection pump lever. The injection pump shutdown
lever is then positioned to the run position (Fig. 13).
When the ignition key is released to the ON posi­
tion, a low- amperage current is supplied to the other
coil i n the solenoid. This is used to hold the solenoid
shaft i n the up position. Accelerator pedal position
then controls fuel lever position for fuel control at the
injection pump.
S E N S O R
E L E C T R I C A L
C O N N E C T O R
I N T A K E
M A N I F O L D
F ( J E L
(UPPER H A L F )
S H U T D O
W N S O L E N O I D ^
S O L E N O I D E L E C T R I C A L
C O N N E C T O R
J9414-93
Fig. 12 Fuel Shutdown Solenoid Location
S H U T D O W N
P O S I T I O N
R U N P O S I T I O N
F U E L
S H U T D O W N
S O L E N O I D
J9414-80
Fig. 13 Fuel Shutdown Solenoid Positions
Voltage to operate the solenoid is supplied from the
ignition switch and through the fuel shutdown solenoid
relay. Also refer to Fuel Shutdown Solenoid Relay.
If the shutdown solenoid is being replaced, its
shaft length must be adjusted. For fuel shutdown
solenoid removal, installation and solenoid shaft
adjustment procedures, refer to the Component
Removal/Installation section of this group.