1999 LAND ROVER DEFENDER Workshop Manual

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DESCRIPTION AND OPERATION EXHAUST GAS RECIRCULATION
The exhaust gas recirculation (EGR) valve permits a controlled amount of exhaust gas to combine with the fresh
air entering the engine. The exhaust gas reduces the combustion temperature by delaying the fuel burning rate,
which assists in reducing the quantity of oxides of nitrogen.
On EU3 models, an EGR cooler is employed to further reduce the combustion temperature. By passing the
exhaust gas through a bundle of pipes flooded by coolant, the density of the exhaust gas going into the engine is
increased. This process further reduces the amount of NO
2in the exhaust.
Recirculation of too much exhaust gas can result in higher emissions of soot, HC and CO due to insufficient air.
The recirculated exhaust gas must be limited so that there is sufficient oxygen available for combustion of the
injected fuel in the combustion chamber. To do this the ECM is used to control the precise quantity of exhaust gas
to be recirculated in accordance with the prevailing operating conditions. Influencing factors include:
The mass of air flow detected by the MAF sensor.
The ambient air temperature detected by the AAP sensor. This is used to initiate adjustments to reduce the
amount of smoke produced at high altitudes.
The mass of air flow detected by the MAF sensor.
The ambient air temperature detected by the AAP sensor. This is used to initiate adjustments to reduce the
amount of smoke produced at high altitudes.
Other factors which are taken into consideration by the engine management system for determining the optimum
operating condition include:
Manifold inlet air temperature
Coolant temperature
Engine speed
Fuel delivered
The main components of the EGR system are as follows.
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DESCRIPTION AND OPERATION EGR MODULATOR
1.Port to vacuum source (white band)
2.Port to EGR valve (blue band)3.Port to atmosphere via in-line filter (green band)
4.Harness connector
The EGR modulator is located on a plate fixed to the inner RH front wing. The modulator is attached to the plate
by two studs, each with two nuts which secure the assembly to a rubber mounting, which helps reduce noise. The
modulator must be mounted vertically with the two vacuum ports uppermost.
Modulator operation is controlled by a signal from the ECM which determines the required amount of EGR needed
in response to inputs relating to air flow, engine operation, and ambient conditions. The modulator has a two pin
connector at its base to connect it to the ECM via the engine harness.
The modulator features three ports:
The top port is identified by a white band and connects to a T-piece in the vacuum line via a small bore light
brown plastic hose. The two other ports on the T-piece connect to the vacuum line hoses of black vinyl tubing
between the vacuum pump and the brake servo assembly attached to the bulkhead. The vacuum pump end of
the tubing terminates in a rubber elbow, which gives a vacuum tight seal on the suction port of the vacuum
pump. The brake servo end of the tubing terminates with a non-return valve in a plastic housing which plugs
into the front face of the brake servo housing.
The middle port is identified by a blue band, and connects to the suction port on the EGR valve through a small
bore blue plastic hose.
The lower port is identified by a green band and connects to atmosphere through an in-line filter via a small
bore green plastic hose.
The blue and brown vacuum hoses are protected by corrugated plastic sheaths. The ends of the hoses are fitted
with rubber boots to ensure vacuum tight seals at the component ports.
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DESCRIPTION AND OPERATION INLET THROTTLE (ILT) MODULATOR
1.Port to vacuum source (white band)
2.Port to ILT valve (blue band)
3.Port to atmosphere via in-line filter (green band)
4.Harness connector (green)
The ILT modulator is located on a plate fixed to the inner wing on the RH side of the engine below the EGR
modulator. The modulator is attached to the plate by two through-studs, each with two nuts which secure the
modulator assembly to a rubber mounting which helps to reduce noise. The modulator must be mounted in the
vertical orientation with the two vacuum ports uppermost.
The modulator operation is controlled by a signal from the ECM which determines the required ratio of exhaust
gas to fresh inlet air needed in response to inputs relating to air flow and engine operating and ambient conditions.
The modulator has a green two-pin connector at its base to connect it to the ECM through the engine harness.
The ILT valve modulator features three ports:
The top port is identified by a white band and connects to a’T’-piece in the vacuum line via a small-bore brown
plastic hose where it is connected in parallel with the vacuum source line to the EGR valve modulator. The two
other ports on the’T’-piece connect vacuum line hoses of black vinyl tubing between the vacuum pump
attached to the alternator and the brake-servo assembly attached to the bulkhead.
The middle port is identified by a blue band and connects to the suction port on the ILT valve through a
small-bore blue plastic hose.
The lower port is identified by a green band and connects to atmosphere through an in-line filter via a green
plastic hose and a three-way connector positioned in-line between the modulators and the filter. The ILT
modulator hose is connected opposite to the two parallel ports at the three-way connector which connect the
vent lines to the EGR valve modulator and the in-line filter. The other port of the in-line filter vents directly to
atmosphere.
The blue and brown vacuum hoses are protected by corrugated plastic sheaths. The ends of the hoses are fitted
with rubber boots to ensure vacuum tight seals at the component ports.
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DESCRIPTION AND OPERATION EGR VALVE
1.EGR valve vacuum port
2.EGR valve assembly
3.Gasket - EGR valve to inlet manifold
4.EGR pipe connection5.Exhaust gas intake
6.Intake air
7.EGR valve open (vacuum applied to EGR valve)
8.EGR valve closed (no vacuum applied to EGR
valve)
The EGR valve is a cast and machined assembly which locates on the front end of the inlet manifold assembly.
The machined faces of the EGR assembly and the inlet manifold are attached attached together using four bolts
passing through the four corners of a flange in the EGR assembly to tappings in the front face of the inlet manifold.
A gasket is used to seal the interface between the EGR valve and the front face of the inlet manifold. The gasket
should be changed every time the EGR valve assembly is removed from the air intake manifold.
The intake side of the EGR valve allows the passage of fresh intercooled air through to the inlet manifold via a
rubber hose which is attached to the front face of the EGR valve assembly by a metal band clamp. The bottom
port of the EGR valve is connected to the EGR pipe using a metal band clamp.
A vacuum port on top of the EGR valve connects the EGR solenoid through a blue, small bore suction hose.
When a vacuum is applied to the EGR valve suction port it causes a spindle with sealing disc (EGR valve) to be
raised, thereby opening the port at the EGR pipe to allow the recirculated exhaust gas to pass through into the
inlet manifold. When the vacuum is removed from the suction port the EGR valve returns to its rest position under
the influence of a spring to tightly close the exhaust gas port. Thus, controlled opening of the EGR valve
determines the mass of recirculated gas allowed to flow through to the inlet manifold.
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DESCRIPTION AND OPERATION INLET THROTTLE (ILT) VALVE
1.EGR valve vacuum port
2.EGR valve assembly
3.Gasket - EGR valve to inlet manifold
4.ILT valve vacuum port
5.ILT valve
6.EGR pipe connection
7.Exhaust gas intake
8.ILT valve - butterfly
9.Intake air
10.EGR valve open (vacuum applied to EGR valve; ILT valve butterfly shown fully open)
11.EGR valve closed (no vacuum to EGR valve; ILT butterfly valve shown fully open)
The ILT valve is used on certain exhaust gas recirculation systems in addition to the standard EGR valve
described above. The ILT valve assembly is mounted at right angles to the EGR valve on the left hand side of the
EGR valve assembly. It is fixed to the EGR valve assembly by three screws.
A vacuum port on top of the ILT valve connects to the ILT modulator though a blue, small-bore suction hose.
When a vacuum is applied to the inlet throttle (ILT) valve suction port, a butterfly valve in the inlet manifold closes
via a spindle and lever mechanism, limiting the supply of fresh intercooled air and creating a depression in the
intake manifold which in turn causes a greater suction at the open port to the EGR delivery pipe. When the
vacuum source is removed from the ILT valve suction port, a spring returns the butterfly to its fully open position.
The ILT valve and EGR valve are operated in conjunction to control the proportional masses of fresh intake air
and recirculated exhaust gas that is allowed to flow through to the inlet manifold.
The EGR valve and ILT valve should be replaced as a single assembly.
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DESCRIPTION AND OPERATION IN-LINE AIR FILTER - PRE EU´ u MODELS
1.To modulator vent port
2.Filter element3.To atmosphere
The in-line air filter is placed in the ventilation line from the EGR modulator. The modulator needs to be able to
vent to atmosphere in order to release the vacuum supplied to the EGR valve. The filter prevents contamination
entering the modulator via the vent port which could cause failure. The filter should be periodically changed in
accordance with the recommended service intervals. The filter is attached to the RH inner front wing, and is held
in position by a clamping bracket. The filter must be mounted vertically.
NOTE: EU3 models are not fitted with an in-line air filter. The ventilation line connects directly to
the air cleaner housing, where it vents to atmosphere.
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DESCRIPTION AND OPERATION EGR SYSTEMS
There are two types of exhaust gas recirculation system used with the Td5 engine dependent on legislation and
market requirements, these are type 1 and type 2.
Type 1 EGR system is fitted to all Td5’s built up to the introduction of 2002 MY, except for Japanese specification
vehicles.
Type 2 EGR system is fitted to all Japanese specification vehicles and was introduced into European markets for
2002 MY to meet EU3 emission requirements. An additional feature introduced at 2002 MY is the EGR cooler,
which is bolted to the front of the cylinder head.
EGR System - Type 1
This EGR system features a modulator which is electrically controlled to modulate a vacuum source to the EGR
valve. The controlled vacuum opens the valve by the amount required to ensure the optimal proportion of exhaust
gas is allowed through to the inlet manifold to be combined with the fresh air intake. Control feedback is achieved
by monitoring the mass of fresh air flowing through the MAF sensor.
EGR modulator operation is controlled by a signal from the ECM, which determines the required amount of EGR
needed in response to inputs relating to air flow and engine operating and ambient conditions. The ECM is
low-side driven, sinking current returned from the vacuum modulator for switching operating condition.
The exhaust gases are routed from the exhaust manifold through a shaped metal pipe which connects to the
underside of the EGR valve. The pipe is held securely in position to the front of the cylinder head using a clamp
bracket. The EGR pipe is attached to a mating port at the front end of the exhaust manifold using 2 Allen screws,
and at the EGR valve assembly by a metal band clamp. The 2 Allen screws should be replaced every time the
EGR pipe is removed.
CAUTION: Extreme caution should be exercised when removing and refitting the EGR pipe to
avoid damage.
When a vacuum is applied to the EGR suction port, it causes a spindle with sealing disc (EGR valve) to be raised,
thus opening the port at the EGR pipe to allow the recirculated exhaust gas to pass through into the inlet manifold.
The valve is spring loaded so that when the vacuum is removed from the suction port the valve returns to its rest
position to tightly close the exhaust gas port.
By controlling the quantity of recirculated exhaust gas available in the inlet manifold, the optimum mix for the
prevailing engine operating conditions can be maintained. This ensures the intake gas to the combustion
chambers will have burning rate properties which will reduce NO
Xemissions to an acceptable level. Normally, full
recirculation is only applicable when NO
Xemissions are most prevalent.
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DESCRIPTION AND OPERATION EGR System - Type 2
This system features twin modulators mounted one above the other on a metal plate located on the inner wing at
the RH side of the engine. The modulators are electrically controlled by the engine management system and are
used to modulate a vacuum source to the EGR valve and a supplementary Inlet Throttle (ILT) valve; the two
valves are controlled to operate in tandem. The ILT valve vacuum pot is mounted adjacent to the EGR valve
housing and has a linkage which connects to a butterfly valve mounted in front of the EGR valve at the air intake
manifold.
The modulator operations are electrically controlled by signals from the engine management system which
determines the required volume of exhaust gas needed in response to inputs relating to air flow, engine operating
conditions and ambient parameters such as temperature and altitude. The engine management ECM switches on
the circuit by completing the path to ground, operating the vacuum modulators.
Pre EU3 models:The exhaust gases are routed from the exhaust manifold through a shaped metal pipe which
connects to the underside of the EGR valve. The pipe is held securely in position to the front of the engine cylinder
head using a metal clamp bracket. The EGR pipe is attached to a mating port at the front end of the exhaust
manifold using two Allen screws and at the EGR valve assembly by a metal band clamp. The two Allen screws
fixing the EGR pipe to the exhaust manifold should be replaced every time the EGR pipe is removed.
CAUTION: Extreme care should be exercised when removing and refitting the EGR pipe to avoid
damage.
EU3 models:The exhaust gases are routed from the exhaust manifold through the EGR cooler to the underside
of the EGR valve. The EGR cooler is bolted to the front of the engine cylinder head. An EGR pipe connects the
EGR cooler to the exhaust manifold and is secured by two Allen screws. The two Allen screws fixing the EGR pipe
to the exhaust manifold should be replaced every time the EGR pipe is removed. A second pipe connects the
EGR cooler to the EGR valve; this pipe is secured to the EGR valve by a clip, and to the cooler by two Allen
screws.
CAUTION: Extreme care should be exercised when removing and refitting the EGR pipe to avoid
damage. When refitting the EGR cooler, always tighten the pipe connections BEFORE tightening
the bolts securing the cooler to the cylinder head.
When a vacuum is applied to the EGR suction port, it causes a spindle with sealing disc (EGR valve) to be raised,
opening the port at the EGR pipe to allow the recirculated exhaust gas to pass through into the inlet manifold. The
valve is spring loaded so that when the vacuum is removed from the suction port, the valve returns to its rest
position to tightly close the exhaust gas port.
A vacuum is simultaneously applied to the inlet throttle (ILT) valve suction port which causes the butterfly valve in
the inlet manifold to close by means of a spindle and lever mechanism. Closing the butterfly valve limits the supply
of fresh intercooled air entering the inlet manifold and causes a depression within the inlet manifold to create a
greater suction at the open port to the EGR delivery pipe. In this condition a greater mass of recirculated exhaust
gas is drawn into the inlet manifold for use in the combustion process. When the vacuum is released from the ILT
valve suction port a spring returns the butterfly valve to its fully open position.
By controlling the quantities of recirculated exhaust gas and fresh intake air available in the inlet manifold, the
optimum mix for the prevailing engine operating conditions can be maintained which ensures the intake gas to the
combustion chambers will have burning rate properties which will reduce the NO
2emissions to an acceptable
level. Normally, full recirculation is only applicable when the NO
2emissions are most prevalent.
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