Diesel Truck Engine Emission System

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 Ford Diesel Engine Emissions

6.0 L Engine, 6.4L Engine, 6.7L Engine, 7.3 L Engine, EGR Valve Testing, Diesel Emission System

Crank Ventilation System:

6.0 L Diesel Engine:Emmision

Closed Crankcase Ventilation (CCV) System:

The Closed Crankcase Ventilation (CCV) system
route’s crankcase blow-by gases from the breather assembly back into the engine
intake airflow to be used for combustion.

6.4 L Diesel Engine:

Closed Crankcase Ventilation (CCV) System:

The Closed Crankcase Ventilation (CCV) system
route’s crankcase blow-by gases from the breather assembly back into the engine
intake airflow to be used for combustion.

6.7 L Diesel Engine:

Crankcase Ventilation:

The crankcase ventilation system, Fig. 43, purges crankcase
gases to the intake manifold. The crankcase ventilation system consists of five
main elements, (1) expansion chamber separator, (2) cyclonic oil separator unit
w/integral pressure limiting valve, (3) stainless steel check valve, (4) oil
collection chamber and (5) pressure regulating valve.

Fig. 43 Crankcase ventilation system operation. Ford 6.7 L
diesel engine:

Crankcase ventilation system

Combustion blow-by gases enter the rear port of crankcase vent assembly and pass
into an expansion chamber where larger oil droplets fallout of blow-by gases
due to a rapid decrease in flow velocity. The remaining blow-by gases flow through
into cyclonic oil separator unit. The blow-by gases are then separated into smaller
cyclone oil separators, which force smaller oil droplets to the side walls, so
they drain out and flow to oil collection chamber.The remaining lighter gases flow
to the intake manifold.

The oil collection chamber has a drain port and a stainless
steel check valve. The check valve allows smaller oil droplets to return to
crankcase while blocking gases in the oil return path. The oil separator works
using cyclonic technology. Therefore, no filter media is required inside
canister. There is an integrated pressure regulating valve on the side of the
cyclonic oil separator which prevents excessive vacuum levels from being
applied to crankcase. Maintenance is not required, and canister is replaced as
an assembly.

Diesel Exhaust Fluid (DEF) System:

6.7 L Diesel Engine:

Reductant Heater & Sender Assembly:

The reductants heater and sender assembly contains a pickup
tube for reductants pump module, an electric heating element, a reductant’s
temperature sensor and an electrode type level sensor. The heating element is
directly above pick-up-tubes inlet filter. When the reductant’s temperature
sensor detects the diesel exhaust fluid temperature dropping to the freezing
point of 12°F (-11°C), the PCM will command the glow plug control module to
provide voltage to heating element. The heating element thaws liquid reductants
within the reductants heater and sender assembly reservoir during cold ambient
temperatures.The reductants level sensor incorporates four stainless
steel electrodes, with three electrodes arranged vertically to provide a high,
middle, and low level signal. The fourth electrode acts as a ground. When the
reductant’s tank is full, DEF closes a circuit between all three-level
electrodes and ground electrode, indicating tank is full. As DEF is consumed,
level drops and uncovers each electrode in sequence. The PCM calculates DEF
level based on these signals.

Reductant Heaters:

The reductant heaters maintain DEF in a liquid state during
cold ambient temperatures. There are three heating elements in the system, each
receiving voltage from the glow plug control module. The reductant tank heater
is integral to the reductant heater and sender assembly. The reductant pump
heater is integral to the reductant pump assembly.

Reductant Injector:

The reductant injector, Fig. 44, is a pulse width modulated
solenoid controlled directly by PCM. The injector receives DEF from reductant
pressure line and sprays it into the exhaust stream, where it is mixed into
exhaust gases before entering SCR catalyst.

Fig. 44 Reductant injector components & location. Ford
6.7L diesel engine:

Reductant injector components & location. Ford 6.7L diesel engine

Reductant Pressure Sensor:

The reductant pressure sensor provides feedback to PCM, which
regulates system pressure by controlling pump speed using pulse width
modulation. The reductant pressure sensor is integral to the reductant pump
assembly.

Reductant Pump Assembly:

The reductant pump assembly contains a diaphragm pressure
pump, a pressure sensor, a purge valve, an outlet filter and an internal
heating element. The reductant pressure sensor provides feedback to PCM, which
regulates system pressure by controlling pump speed using pulse width
modulation. When PCM request’s reductant injection, the reductant injector
opens and the pump operates, filling reductant pressure line and injector and
purging air from the system. When all air is purged, injector closes and pump
builds pressure to 73 psi. (500 kPa). The system is then primed, and injector
provides DEF to the SCR catalyst as determined by PCM.

When the vehicle is shut down, PCM closes injector and
actuates reductant purge valve, causing the pump to reverse flow and bleed down
pressure on reductant pressure’s lines. The PCM then opens injector to allow
gas to enter reductant pressure line, which in turn allows the pump to purge
all remaining DEF from the system and return it to the reductant tank. The PCM
closes injector, and returns purge valve to the forward position. The PCM
commands the glow plug control module to provide voltage to the reductant pump
assembly internal heating element when reductant temperature approaches 12°F
(-11°C).

Reductant Purge Valve:

The reductant purge valve allows the reductant pump assembly
to reverse flow and purge system when requested by PCM. The reductant purge
valve is integral to the reductant pump assembly.

Diesel Oxidation Catalyst (DOC):

6.0 L & 7.3 L Diesel Engines:

Description:

The purpose of the exhaust catalyst and exhaust system, Fig.
29, is to convey the exhaust gas from the engine to the atmosphere and reduce
the tailpipe emissions of hydrocarbon (HC), carbon monoxide (CO), oxides of
nitrogen (NOx) and diesel particulates.

The exhaust gas and particulates are directed away from the
engine through the exhaust manifold. The exhaust gas concentrations are then
reduced to acceptable levels as the exhaust gas passes through the Diesel
Oxidation Catalyst (DOC). Since the particulates are components of the exhaust
gas, some soot particulates may deposit on the DOC. The reduced emissions
exhaust gas, and any remaining particulates flow through the muffler and
tailpipe into the atmosphere.

The converter body should be inspected for distortion and
other types of damage. Excessive heat can bulge or distort the converter or
filter. Furthermore, inspect for missing or improperly installed converter heat
shields.

6.4 L Diesel Engine:

Diesel Particulate Filter (DPF):

The DPF, Fig. 45, collects soot and ash particles that are
present in exhaust gas of diesel engines. The DPF assembly typically consists
of active precious metals deposited on a substrate filter. The exhaust gas is
forced to flow through walls of porous substrate and exit through adjoining
channels. The particulates that are larger than the pore size of walls are trapped
for regeneration. During regeneration temperature in DPF increases to be
greater than 1022°F (550°C); at this temperature, soot in DPF burns and becomes
ash. The precious metal coating promotes regeneration of trapped particulates
through heat generating reaction and catalyzes untreated exhaust gas. The
substrate filter is held in the metal shell by a ceramic fiber support system.
The support system makes up size differences that occur due to thermal
expansion and maintain a uniform holding force on substrate filter.

Fig. 45 Catalytic Oxidation Catalyst (DOC), Diesel
Particulate Filter (DPF) & exhaust system. Ford 6.4 L diesel engine:

Particulate Filter (DPF) & exhaust system. Ford 6.4L diesel engine.

Diesel Particulate Filter (DPF) Pressure Sensor:

The DPF pressure sensor is an input to PCM and is used to
measure pressure before DPF. The sensor is a differential type sensor that is
referenced to atmospheric pressure. At key On, engine Off DPF pressure sensor
pressure value reads 0 psi. (0 kPa). The range of the sensor is 0 to 11.6 psi.
(0 to 80 kPa).

The converter body and diesel particulate filter should be
inspected for distortion and other types of damage. Excessive heat can bulge or
distort the converter or filter. Furthermore, inspect for missing or improperly
installed converter heat shields.

6.7 L Diesel Engine

Diesel Particulate Filter (DPF)

The diesel particulate filter, Fig. 46, collects soot and
ash particles that are present in the exhaust gas of diesel engines. The diesel
particulate filter assembly typically consists of active precious metals
deposited on a substrate filter. The exhaust gas is forced to flow through
walls of porous substrate and exit through adjoining channels. The particulates
That is larger than the pore size of the walls are trapped for regeneration. During
Regeneration temperature in the DPF increases to be greater than 1022°F (550°C).
The precious metal coating promotes regeneration of trapped particulates
through heat generating reaction and catalyzes untreated exhaust gas. The
substrate filter is held in a metal shell by a ceramic fiber support system.
The support system makes up size differences that occur due to thermal
expansion and maintains a uniform holding force on the substrate filter.

Fig. 46 Diesel Particulate Filter (DPF). Ford 6.7L diesel engine:

 

Diesel Particulate Filter

The converter body and diesel particulate filter should be
inspected for distortion and other types of damage. Excessive heat can bulge,
distort the converter, or filter. Furthermore, inspect for missing or
improperly installed converter heat shields.

Diesel Particulate Filter (DPF) Pressure Sensor:

The diesel particulate filter pressure sensor is an input to
CM, and measures pressure before DPF. The sensor is a differential type sensor
that is referenced to atmospheric pressure and is located in the exhaust system
downstream of DPF. At key On, engine Off, the DPF pressure sensor pressure
value reads 0 psi. (0 kPa). The range of the sensor is 0 to 11.6 psi (0 to 80
kPa). The PCM calculates the soot load based on DPF pressure and initiates
regeneration when the soot load reaches the specified limit.

 

EGR System:

                       Diesel 

                                                      Engine EGR Valve System

With engine at normal operating temperature, vacuum should be applied to the EGR valve at idle speed.

  1. Ensure all vacuum hoses are properly routed,
    securely attached and undamaged.
  2. Disconnect and plug EGR vacuum supply hose at
    EGR valve.
  3. Connect a suitable hand held vacuum pump to
    EGR valve vacuum port, then gradually apply 12 inches of vacuum.
  4. Observe vacuum gauge on vacuum pump for loss
    of vacuum. If a loss is present, replace the EGR valve.
  5. Release vacuum of the EGR valve and listen for
    sound of valve hitting seat.

6.0 L Diesel Engine

EGR Valve:

The EGR system reduces peak combustion temperatures and NOx.
The EGR valve, Fig. 47, is an electromechanical device that uses a linear
actuator to control relative position of the valve pintle. This device also has
a built-in pintle position sensor that functions to provide PCM with a feedback
signal.

Fig. 47

 

 

EGR Valve

EGR valve location. Ford 6.0 L diesel engine:

 

EGR valve location. Ford 6.0L diesel engine

Inspect the system for proper installation of EGR valve,
control switches, and sensors. Inspect for proper connection of electrical
connectors and mechanical linkage.

EGR Actuator & Valve Position Sensor:

The EGR actuator is a variable position valve that controls
the amount of exhaust that enters the intake manifold. The EGR actuator is
controlled by PCM using a pulse width modulated signal that varies from 0-100%.
The EGR actuator consists of two components, a valve with an actuator and a
position sensor to monitor valve movement. The EGR valve position sensor is a
potentiometer sensor, which is needed to give control circuit feedback to
achieve the desired travel position. When the EGR receives a 5 volt reference
signal and a ground from PCM, a linear analog voltage signal from the sensor indicates
the position of EGR valve. Input signals from the manifold absolute pressure,
Exhaust pressure, and BARO sensors are used by PCM to determine the EGR system
flow.

EGR System Cooler:

The exhaust gasses are directed through EGR system cooler to
remove heat before gasses arrive at EGR valve. Engine coolant is used to reduce
exhaust gas temperature by directing coolant flow through the EGR system
cooler.

EP Sensor:

The EP sensor is a variable capacitor sensor that is
supplied a 5 volt reference signal by PCM and returns a linear analog voltage
signal that indicates pressure. The EP sensor measures pressure in the LH
exhaust manifold. The sensor feedback signal is used for VGT and EGR valve
control.

6.4 L Diesel Engine:

Exhaust Gas Recirculation (EGR) Oxidation Catalytic
Converter (OC)

The EGR OC, Fig. 48, helps keep EGR coolers clean by
removing deposits and exhaust condensation and preventing corrosion in
downstream components.

Fig. 48 Exhaust Gas Recirculation (EGR) Oxidation Catalytic
Converter (OC). Ford 6.4L diesel engine:

 

6.4L Diesel Engine

Exhaust Gas Re-circulation (EGR) Coolers:

The exhaust gasses are directed through two EGR coolers,
Fig. 49, to remove heat before gasses arrive at EGR valve. Engine coolant is
used to reduce exhaust gas temperature by directing coolant flow through EGR
coolers.

Fig. 49 Exhaust Gas Recirculation (EGR) coolers. Ford 6.4 L
diesel engine:

 

Exhaust Gas Recirculation (EGR) Coolers

Exhaust Gas Re-circulation Temperature (EGRT) Sensor:

The EGRT sensor is a thermistor device that monitors exhaust
gas temperature before EGR coolers. The electrical resistance of a thermistor
decreases as temperature increases and increases as the temperature decreases.
The varying, non-linear resistance affects voltage drop across sensor terminals
and provides an electrical signal to PCM that corresponds to measured
temperature. The EGRT sensor is used to determine whether EGR coolers are
operating correctly.

Exhaust Gas Re-circulation Temperature 2 (EGRT2) Sensor:

The EGRT2 sensor is a thermistor device that monitors
exhaust gas temperature after EGR coolers. The electrical resistance of a
thermistor decreases as temperature increases and increases as the temperature
decreases. The varying, non-linear resistance affects voltage drop across
sensor terminals and provides an electrical signal to PCM that corresponds to
measured temperature. The EGRT2 sensor is used to determine whether EGR coolers
are operating correctly.

Exhaust Gas Re-circulation (EGR) Valve:

The EGR valve is a variable position valve that controls the
amount of exhaust that enters the intake manifold. The PCM controls the EGR
valve, which operates between -100 and 100% duty cycles, which cannot be viewed
by a scan tool.

Exhaust Gas Re-circulation (EGR) Valve Position Sensor:

The EGR valve position sensor is a potentiometer sensor that
monitors EGR valve movement. The valve position signal is monitored for the
desired EGR valve travel position. The sensor is integral to EGR valve.

6.7 L Diesel Engine:

EGR Cooler:

The EGR cooler, Fig. 50, removes heat from exhaust gases
before gases enter the intake manifold. The EGR cooler is located above RH
valve cover. When exhaust gases are directed through EGR cooler, coolant from
the secondary cooling system reduces exhaust gas temperature. The exhaust gases
are directed through EGR cooler by a Power train control module (PCM) controlled EGR cooler bypass valve.

Fig. 50 EGR cooler. Ford 6.7 L diesel engine:

 

EGR Cooler

EGR Cooler Bypass Valve:

The exhaust gases are directed through an EGR cooler by EGR
cooler bypass valve, Fig. 51, to remove heat before entering the intake manifold.
The EGR cooler bypass valve is internal to EGR cooler and mounted to RH valve
cover, below EGR valve. When EGR cooler bypass valve solenoid is commanded to
0% duty cycle by PCM, EGR cooler bypass valve is closed. When EGR cooler bypass
valve is closed, exhaust gases pass through EGR cooler to the intake manifold.
When EGR cooler by pass valve solenoid is commanded to 100% duty cycle by PCM,
EGR cooler bypass valve is opened. When the EGR cooler bypass valve is open,
exhaust gases pass directly to the intake manifold without passing through EGR
cooler.

Fig. 51 EGR cooler bypass valve. Ford 6.7 L diesel engine:

 

EGR cooler bypass valve.

EGR Cooler Bypass Valve Solenoid:

The EGR cooler bypass valve solenoid is a PCM controlled
vacuum solenoid. The EGR cooler bypass valve solenoid controls EGR cooler
bypass valve position by applying vacuum from the vacuum pump to EGR cooler
bypass valve actuator. The EGR cooler bypass valve solenoid is located at the
top front of EGR cooler. When the EGR cooler bypass valve solenoid is commanded
to 0% duty cycle by powertrain control module (PCM), no vacuum from the vacuum
pump is applied to EGR cooler bypass valve actuator and EGR cooler bypass valve
is closed. When the EGR cooler bypass valve is closed, exhaust gases pass through
EGR cooler to the intake manifold. When EGR cooler bypass valve solenoid is
commanded to 100% duty cycle by PCM, vacuum from the vacuum pump is applied to
EGR cooler bypass valve actuator and the EGR cooler bypass valve is opened.
When the EGR cooler bypass valve is open, exhaust gases pass directly to the
intake manifold without passing through EGR.

Exhaust Gas Recirculation Temperature (EGRT) Sensor:

The EGRT sensor is a thermistor type sensor. The EGRT sensor
is an input to PCM and monitors the exhaust gas temperature after EGR cooler.
The electrical resistance of the sensor increases as temperature decreases and
resistance decreases as temperature increases. The varying resistance changes
voltage drop across sensor terminals and provides electrical voltage to PCM
corresponding to temperature. The EGRT sensor is used to determine if EGR
cooler is operating properly.

EGR Valve:

The EGR valve is a variable position valve that controls the
amount of exhaust that enters the intake manifold. The PCM controls EGR valve,
which operates between 0 and 100% duty cycles. The EGR valve operation can be
Monitored by viewing EGRVP PID, which displays the EGR valve position. The EGR valve
Position sensor is an integral EGR valve.

Inspect the system for proper installation of the EGR valve,
control switches and sensors. Inspect for proper connection of electrical
connectors and mechanical linkage.

Selective Catalytic Reduction (SCR) System:

6.7 L Diesel Engine:

The SCR catalyst, Fig. 52, reduces NOx present in the
exhaust stream to nitrogen (N2) and water (H2O). At the inlet of SCR catalyst
is a port for reductant injector, followed by a louvered diffuser and a twist
mixer. DEF (Diesel Exhaust Fluid) is a solution of urea in deionized water.
When DEF is introduced into the system, it finely atomizes in louvered diffuser
and mixes evenly with exhaust gases in the twist mixer. During this time, heat
of exhaust gases causes urea to split into carbon dioxide (CO2) and ammonia
(NH3). As the ammonia and NOx pass over the SCR catalyst, a reduction reaction
takes place, and ammonia and NOx are converted to N2 and H2O. This reaction
takes place at up to 95% efficiency and allows the engine to run leaner and more
efficiently, since the high NOx levels that are produced under lean conditions
are eliminated.

Fig. 52 SCR catalyst. Ford 6.7 L diesel engine:

 

SCR catalyst. Ford 6.7L diesel engine

 

The SCR system should be inspected for damaged and missing
components. The instrument panel DEF indicator should be checked to ensure the
DEF tank is sufficiently filed. If the vehicle does not have DEF indicator,
check the tank fluid level.

Turbocharger:

The turbocharger increases engine power by pumping
compressed air into the combustion chambers, allowing a greater quantity of
fuel to combust at the optimal air/fuel ratio. The turbine spins as exhaust gas
flows out of the engine and over turbine blades and turns the compressor wheel
at other ends of the turbine shaft, pumping more air into the intake system.

 

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