1999 DODGE RAM heater

converter lock-up. ECM uses various input signals such as transmission
temperature, output shaft speed, central module timer, engine speed,
APPS and brake switch position to determine operation of transmission
torque converter clutch solenoid. Transmission torque converter clutch
solenoid is located on transmission valve body.
FUEL SYSTEM
FUEL DELIVERY
Fuel Injection Pump
A camshaft-driven Bosch VP44 in-line fuel injection pump is
used to supply high pressure fuel to each fuel injector in precise
metered amounts at the correct time. See Fig. 2. The pump is timed to
camshaft gear. Pump output is controlled by integral Fuel Pump Control
Module (FPCM). Because of electronic control, idle speeds and pump
timing are not adjustable. See ON-VEHICLE ADJUSTMENTS - TRUCKS -
DIESEL article. FPCM can operate engine if crankshaft position sensor
signal does not exist. Fuel injection occurs near completion of
compression stroke for each cylinder.
Fuel injection pump contains an overflow valve which allows
excess fuel to return to the fuel tank. Overflow valve is located on
side of fuel injection pump and is used to attach the fuel return line
to the fuel injection pump.
Fuel Transfer Pump
Fuel transfer pump is located on driver's side of cylinder
block, above starter. See Fig. 2. A 12 volt, 12-amp electric vane-type
pump supplies low fuel pressure from fuel tank, through fuel
heater/fuel filter/water separator to fuel injection pump. Fuel
transfer pump contains internal check valves to prevent fuel from
bleeding back into fuel tank during engine shutdown. Pump will self
prime with ignition on for 2 seconds. Pump has 2 modes, 100 percent
duty cycle (10 psi) when engine is running and 25 percent duty cycle
(7 psi) when engine is cranking.
Fuel Filter/Water Separator
Fuel filter/water separator, located on left side of engine,
protects injection pump by removing water and contaminants from fuel.
See Fig. 2 . Assembly also includes fuel heater and Water-In-Fuel (WIF)
sensor.
In-Tank Fuel Filter
A separate in-tank fuel filter is attached to bottom of fuel
tank module. In-tank fuel filter does not require service under normal
conditions.
FUEL CONTROL
Fuel Injector
Fuel injector delivers atomized fuel into the cylinder.
During fuel injection, fuel pressure from fuel injection pump
increases to fuel injector opening pressure or pop pressure of 4500
psi (316 kg/cm

). This is the pressure required to lift fuel injector
needle valve from its seat, allowing fuel to be injected into the
cylinder. Once fuel pressure decreases to less then the opening
pressure, a spring forces needle valve closed and stops fuel injection
into the cylinders. Each fuel injector is connected to injection pump
by a high pressure (as much as 17,405 psi) line.
Fuel Injection Timing
Pump output is controlled by integral Fuel Pump Control

Module (FPCM). Because of electronic control, pump timing is not
adjustable. See ON-VEHICLE ADJUSTMENTS - TRUCKS - DIESEL article.
FUEL FILTER/WATER SEPARATOR
Fuel filter/water separator is located on left side of engine
and contains fuel heater, Water-In-Fuel (WIF) sensor and drain valve.
See Fig. 2 . The WIF sensor delivers an input signal to Engine Control
Module (ECM) when water exists in fuel filter/water separator. ECM
will then turn on WATER-IN-FUEL warning light. WATER-IN-FUEL warning
light is located on instrument panel, just below tachometer. The
WATER-IN-FUEL warning light informs the operator to drain water from
fuel filter/water separator to prevent damage to fuel system
components. Water may be drained from fuel filter/water separator by
using drain valve on fuel filter/water separator.
FUEL HEATER
Fuel heater is used to prevent diesel fuel from waxing during
cold temperatures. Fuel heater is located in fuel filter/water
separator. See Fig. 2. Fuel flows from fuel tank to fuel transfer pump
and then to fuel filter/water separator. Fuel heater contains a fuel
heater temperature sensor that senses the fuel temperature. When
temperature is less than 37-53
F (3-12C), fuel heater temperature
sensor allows current to flow to the fuel heater to warm the fuel.
When temperature is more than 67-83
F (19-28C), fuel heater
temperature sensor turns off the current flow to the fuel heater.
Voltage to operate fuel heater is provided from ignition switch,
through fuel heater relay and to fuel heater. Fuel heater and fuel
heater relay are not controlled by Engine Control Module (ECM).
EMISSION SYSTEMS
INTAKE MANIFOLD AIR HEATER SYSTEM
Intake manifold air heater is used to warm intake air during
cold starting conditions. Heater system consists of 2 relays and 2
grid heaters installed on top of intake manifold. See Fig. 5.
Engine Control Module (ECM) energizes intake manifold air
heater relays to provide voltage to intake manifold air heater before
and after starting depending on input signals from intake manifold air
temperature sensor, engine speed sensor and vehicle speed. Intake
manifold air heater relays are not energized when intake manifold air
temperature is greater than 59
F (15C) or during engine cranking.
Intake manifold air heater relays are mounted on left inner wheelwell,
below left side battery. See Fig. 6.
Intake manifold air temperature sensor monitors intake
manifold air temperature and delivers an input signal to ECM for
controlling intake manifold air heater. Intake manifold air
temperature sensor is located in intake manifold. See Figs. 2 and 4.
SELF-DIAGNOSTIC SYSTEM
DATA LINK CONNECTOR
The Data Link Connector (DLC) is a 16-pin connector located
at lower edge of driver's side of instrument panel, just above the
accelerator pedal. The Engine Control Module (ECM) contains a self-
diagnostic system which stores a Diagnostic Trouble Code (FTC) if an
incorrect signal or no signal is received from certain sensors or
components. FTC may be retrieved from ECM for system diagnosis by

operating. When ground is supplied to injector by PCM, armature and
pintle inside injector move a short distance against spring and open a
small orifice. Since fuel is under high pressure, a fine spray is
developed.
Modes Of Operation
As input signals to PCM change, PCM adjusts its response to
output devices. Modes of operation come in 2 types, open loop and
closed loop. In open loop mode, PCM is not using input from HO2S and
is responding to preset programming to determine injector pulse width
and ignition timing. In closed loop mode, PCM adjusts ignition timing
and uses input from HO2S to fine tune injector pulse width.
The following inputs may be used to determine PCM mode:
* A/C Control Positions
* A/C Switch
* Battery Voltage
* Brake Switch
* Camshaft Position (CMP) Sensor
* Crankshaft Position (CKP) Sensor
* Engine Coolant Temperature (ECT) Sensor
* Engine Speed (RPM)
* Heated Oxygen Sensor (HO2S)
* Intake Air Temperature (IAT) Sensor
* Manifold Absolute Pressure (MAP) Sensor
* Park/Neutral (P/N) Switch
* Starter Relay
* Throttle Position (TP) Sensor
* Vehicle Speed Sensor (VSS)
From these inputs, PCM determines which mode vehicle is in
and responds appropriately. Not all inputs are used in all modes or by
all models. Modes of operation are:
* Ignition Switch On (Engine Not Running) - This is an open
loop mode. PCM pre-positions IAC motor based on ECT sensor
input. PCM determines atmospheric pressure from MAP sensor
and determines basic fuel strategy. PCM modifies fuel
strategy according to IAT sensor, ECT sensor and TP sensor
inputs. PCM activates ASD relay, which in turn activates fuel
pump for only 2 seconds unless engine is cranked. PCM also
energizes HO2S heater element for approximately 2 seconds
unless engine is cranked.
* Engine Start-Up - This is an open loop mode. When starter is
engaged, PCM receives input from battery voltage, ignition
switch, CKP sensor, CMP sensor, ECT sensor, IAT sensor, MAP
sensor and TP sensor. Based on these inputs, voltage is
applied to fuel injectors with PCM controlling injection
sequence, rate, and pulse width. PCM provides ground for
injectors to fire in proper order.
PCM determines proper ignition timing according to input
received from CKP sensor. If PCM does not receive CKP sensor signal
within 3 seconds after engine begins cranking, fuel injection system
is shut down and a Diagnostic Trouble Code (FTC) is set in PCM memory.\
* Engine Warm-Up - This is an open loop mode. PCM determines
injector pulse width using input information from battery
voltage, CKP sensor, CMP sensor, ECT sensor, IAT sensor, MAP
sensor and TP sensor. PCM also monitors A/C request and P/N
switch (A/T only) for fuel calculation. PCM controls engine
idle speed through IAC motor. PCM controls ignition timing
based on CKP sensor input.