Dodge RAM TRUCK 1500 1995 Service Manual page 1096

14 -14 FUEL DELIVERY SYSTEM—DIESEL ENGINE
FUEL TEMPERATURE SENSOR
Fig. 4 Fuel Heater and Temperature Sensor Location
Voltage to operate the fuel heater is supplied from
the ignition switch and through the fuel heater relay
(Fig. 5) (also refer to Fuel Heater Relay).
The fuel heater and fuel heater relay are not con­
trolled by the powertrain control module (PCM).
The built-in heater element operates on 12 volts,
300 watts at 0 degrees F.
The fuel heater assembly contains a pre-filter to
prevent contaminants from entering the fuel transfer
pump.
For diagnosis, refer to the Diesel Engine—General
Diagnosis section of this group.
For removal and installation procedures, refer to
the Diesel Engine—Component Removal/Installation
section of this group.
— — - B R
FUEL HE1TER RELAY • • . ,
Voltage to operate the fuel heater is supplied from
the ignition switch through the fuel heater relay. The
powertrain control module (PCM) is not used to con­
trol this relay.
The fuel heater relay is located in the engine com­
partment near the brake master cylinder (Fig. 5).
FUEL SHUT-OFF
FUEL HEATER SOLENOID RELAY
Fig. 5 Fuel Heater Relay—Diesel
For diagnosis, refer to the Diesel Engine—General
Diagnosis section of this group.
For removal and installation procedures, refer to
the Diesel Engine—Component Removal/Installation
section of this group.
FUEL TANK
Refer to the Fuel Tank section of this group for in­
formation.
FUEL TRANSFER PUMP
The fuel transfer pump (fuel lift pump) is located
on the left-rear side of the engine cylinder block
above the starter motor (Fig. 1). This mechanically
operated pump is not controlled by the powertrain
control module (PCM).
The purpose of the fuel transfer pump is to supply
(transfer) a low-pressure fuel source of approximately
172 Kpa (25 psi) to the injection pump and fuel filter/
water separator from the fuel tank. Here, the low-
pressure is raised by the fuel injection pump for
operation of the high-pressure fuel injectors. The
transfer pump is driven by an eccentric on the engine
camshaft that actuates a spring loaded piston within
the pump (Fig. 6). Check valves within the pump,
on the top of the fuel tank module (Fig. 2). This fit­
ting will be available only on: diesel powered models,
and models with either a 5.9L V-8 heavy duty or 8.0L
V-10 engine, and all cab-chassis models. This fitting
supplies a non-pressurized auxiliary fuel source.
FUEL HEATER
The fuel heater is used to prevent diesel fuel from
waxing during cold weather operation. The fuel
heater is located on the left side of the engine above
the starter motor (Fig. 4).
The heater assembly is equipped with a built-in
sensor (thermostat) (Fig. 4) that senses fuel temper­
ature. When the temperature is below 40 degrees F,
the built-in sensor allows current to flow to the
built-in heater element warming the fuel. When the
temperature is above 80 degrees F, the sensor stops
current flow to the heater element.