engine LAND ROVER DISCOVERY 2002 Workshop Manual

EMISSION CONTROL - V8
17-2-16 DESCRIPTION AND OPERATION
Fuel leak detection system (vacuum type) – NAS only
The advanced evaporative loss control system equipped with a vacuum type, fuel evaporation leak detection
capability is similar to the standard evaporative loss system, but also includes additional components to enable the
engine control module (ECM) to perform a fuel evaporation leak detection test. The system includes an EVAPs
canister and purge valve, and in addition, a canister vent solenoid (CVS) valve and a fuel tank pressure sensor.
The function of the CVS valve is to block the atmospheric vent side of the EVAP canister under the control of the ECM
so that an evaporation system leak check can be performed. The test is carried out when the vehicle is stationary and
the engine is running at idle speed. The system test uses the natural rate of fuel evaporation and engine manifold
depression. Failure of the leak check will result in illumination of the Malfunction Indicator Lamp (MIL).
The fuel evaporation leak detection is part of the On-Board Diagnostics (OBD) strategy and it is able to determine
vapour leaks from holes or breaks greater than 1 mm (0.04 in.) in diameter. Any fuel evaporation system leaks which
occur between the output of the purge valve and the connection to the inlet manifold cannot be determined using this
test, but these will be detected through the fuelling adaption diagnostics.
Fuel leak detection system (positive pressure type) – NAS only
The evaporative loss control system equipped with a positive pressure type, fuel evaporation leak detection capability
is similar to the vacuum type, but it is capable of detecting smaller leaks by placing the evaporation system under the
influence of positive air pressure. The system includes an EVAPs canister and purge valve, and in addition, a leak
detection pump comprising a motor and solenoid valve.
The solenoid valve contained in the leak detection pump assembly performs a similar function to the CVS valve
utilised on the vacuum type pressure test. The solenoid valve is used to block the atmospheric vent side of the EVAP
canister under the control of the ECM so that an EVAP system leak check can be performed. At the same time,
pressurised air from the pump is allowed past the valve into the EVAP system to set up a positive pressure. The test
is carried out at the end of a drive cycle when the vehicle is stationary and the ignition is switched off. The test is
delayed for a brief period (approximately 10 seconds) after the engine is switched off to allow any slosh in the fuel
tank to stabilise. Component validity checks and pressure signal reference checking takes a further 10 seconds before
the pressurised air is introduced into the EVAP system.
During reference checking, the purge valve is closed and the leak detection pump solenoid valve is not energised,
while the leak detection pump is operated. The pressurised air is bypassed through a restrictor which corresponds to
a 0.5 mm (0.02 in) leak while the current consumption of the leak detection pump motor is monitored.
The system test uses the leak detection pump to force air into the EVAP system when the purge valve and solenoid
valves are both closed (solenoid valve energised), to put the evaporation lines, components and fuel tank under the
influence of positive air pressure. Air is drawn into the pump through an air filter which is located in the engine
compartment.
The fuel leak detection pump current consumption is monitored by the ECM while the EVAP system is under pressure,
and compared to the current noted during the reference check. A drop in the current drawn by the leak detection pump
motor, indicates that air is being lost through holes or leaks in the system which are greater than the reference value
of 0.5 mm (0.02 in). An increase in the current drawn by the leak detection pump motor, indicates that the EVAP
system is well sealed and that there are no leaks present which are greater than 0.5 mm (0.02 in).
The presence of leakage points indicates the likelihood of hydrocarbon emissions to atmosphere from the
evaporation system outside of test conditions and the necessity for rectification work to be conducted to seal the
system. Failure of the leak check will result in illumination of the Malfunction Indicator Lamp (MIL).
C0637-9 Fuel tank pressure sensor (NAS vehicles
with vacuum type EVAP system leak
detection only)Output reference 5V
C0637-12 Analogue fuel level (NAS vehicles with
positive pressure type EVAP system leak
detection only)Input Analogue 0 - 5V
C0637-14 Fuel tank pressure sensor (NAS vehicles
with vacuum type EVAP system leak
detection only)Input signal Analogue 0 - 5V
C0637-20 MIL "ON" Output drive Switch to ground Connector / Pin No. Function Signal type Control

EMISSION CONTROL - V8
17-2-18 DESCRIPTION AND OPERATION
EVAP (charcoal) canister
1EVAP canister
2Port to breather tube
3Port – vent line from fuel tank
4Port – purge line
The EVAP canister is mounted on a bracket fitted beneath the vehicle on the RH side of the chassis. The EVAP
canister ports face towards the front of the vehicle. The EVAP canister has inscriptions next to each port for
identification of the 'purge', 'tank' and 'air' connections.
The purge line from the EVAP canister is connected to the back of the inlet manifold plenum, after the throttle body
via a purge valve. The pipe between the EVAP canister and the purge valve is routed over the transmission and into
the LH side of the engine bay. The pipe clips to the purge port on the EVAP canister by means of a straight quick-fit
connector and the connection is covered by a rubber seal which is held in position on the port stub pipe.
The vent line from the fuel tank to the EVAP canister connects to the vent port on the canister by means of an elbowed
quick-fit connector. The line passes along the chassis behind the EVAP canister and terminates in a straight female
quick-fit connector to the fuel vent line at the fuel filler.
The plastic pipe to the atmosphere vent line connects to the port on the EVAP canister by means of a short rubber
hose and metal band clips. The atmosphere end of the plastic pipe terminates in a quick fit connector to the pipe
leading to the CVS unit on NAS vehicles with vacuum type, EVAP system leak detection and two snorkel tubes
situated behind the engine at the bulkhead on ROW vehicles. The bore of the plastic breather pipe is larger on NAS
vehicles than on ROW vehicles.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-19
For NAS vehicles with positive pressure, EVAP system leak detection capability, the atmosphere vent line from the
EVAP canister connects to a port on the fuel leak detection pump via a short, large bore hose which is secured to the
component ports by crimped metal clips at each end. A large bore plastic hose from the top of the leak detection pump
is routed to the RH side of the engine bay where it connects to an air filter canister. Under normal operating conditions
(when the fuel leak detection solenoid valve is not energised), the EVAP canister is able to take in clean air via the
air filter, through the pipework and past the open solenoid valve to allow normal purge operation to take place and
release any build up of EVAP system pressure to atmosphere.
The EVAP system pipes are clipped at various points along the pipe runs and tied together with tie straps at suitable
points along the runs.
The NAS and ROW EVAP canisters are of similar appearance, but use charcoal of different consistency. The ROW
vehicles use granular charcoal of 11 bwc (butane working capacity) and NAS vehicles use pelletised charcoal with a
higher absorption capacity of 15 bwc. All canisters are of rectangular shape and have capacities of 1.8 litres (3 1/8
imp. pts) with purge foam retention.
Purge valve
1Direction of flow indicator
2Inlet port – from EVAP canister
3Outlet port – to inlet manifold
4Integral electrical connector
The EVAP canister purge valve is located in the engine bay at the LH side of the engine intake manifold. The valve
is held in position by a plastic clip which secures the inlet pipe of the purge valve to a bracket mounted at the rear of
the engine compartment. On NAS vehicles with secondary air injection, the purge valve is fixed to a metal bracket
together with the SAI vacuum solenoid valve; the purge valve is fixed to the bracket by two plastic clips.
A nylon pipe connects the outlet of the purge valve to the stub pipe on the plenum chamber via a short rubber hose.
The connector to the plenum chamber is a quick-release type, plastic 90
° female elbow; the connection is covered by
a rubber seal which is held in position on the port stub pipe.
A service port is connected in line between the EVAP canister and the inlet side of the purge valve and is rated at 1
psi maximum regulated pressure. The service port must be mounted horizontally and is located close to the bulkhead
at the rear of the engine bay. The service point is used by dealers for pressure testing using specialist nitrogen test
equipment for localising the source of small leaks.
The purge valve has a plastic housing, and a directional arrow is moulded onto the side of the casing to indicate the
direction of flow. The head of the arrow points to the outlet side of the valve which connects to the plenum chamber.

EMISSION CONTROL - V8
17-2-20 DESCRIPTION AND OPERATION
Purge valve operation is controlled by the engine control module (ECM). The purge valve has a two-pin electrical
connector which links to the ECM via the engine harness. Pin-1 of the connector is the power supply source from fuse
2 in the engine compartment fusebox, and pin-2 of the connector is the switched earth from the ECM (pulse width
modulated (PWM) signal) which is used to control the purge valve operation time. Note that the harness connector
for the purge valve is black, and must not be confused with the connector for the Secondary Air Injection
vacuum solenoid valve which is grey.
When the purge valve is earthed by the ECM, the valve opens to allow hydrocarbons stored in the EVAP canister to
be purged to the engine inlet manifold for combustion.
If the purge valve breaks or becomes stuck in the open or closed position, the EVAP system will cease to function
and there are no default measures available. The ECM will store the fault in memory and illuminate the MIL warning
lamp if the correct monitoring conditions have been achieved (i.e. valve status unchanged for 45 seconds after engine
has been running for 15 minutes). If the purge valve is stuck in the open position, a rich air:fuel mixture is likely to
result at the intake manifold, this could cause the engine to misfire and the fuelling adaptions will change.
The following failure modes are possible:
lSticking valve
lValve blocked
lConnector or harness wiring fault (open or short circuit)
lValve stuck open
If the purge valve malfunctions, the following fault codes may be stored in the ECM diagnostic memory, which can be
retrieved using 'Testbook':
P-code Description
P0440Purge valve not sealing
P0444Purge valve open circuit
P0445Purge valve short circuit to ground
P0443Purge valve short circuit to battery voltage

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-21
Canister Vent Solenoid (CVS) unit – (NAS with vacuum type, fuel evaporation leak detection system only)
1CVS unit
2Mounting bracket
3Spring clips to pipe from EVAP canister
4Harness connector
The canister vent solenoid (CVS) valve is mounted on a slide-on bracket which is riveted to the cruise control bracket
at the right hand side of the engine compartment. The vent pipe from the EVAP canister is connected to a stub pipe
on the CVS unit via a hose and plastic pipe combination. A two-pin connector links to the engine management ECM
via the engine harness for solenoid control; one of the wires is the supply feed from fuse No.2 in the engine
compartment fusebox, the other wire is the valve drive line to the ECM. The solenoid is operated when the ECM
grounds the circuit.
The valve is normally open, allowing any build up of air pressure within the evaporation system to escape, whilst
retaining the environmentally harmful hydrocarbons in the EVAP canister. When the ECM is required to run a fuel
system test, the CVS valve is closed to seal the system. The ECM is then able to measure the pressure in the fuel
evaporative system using the fuel tank pressure sensor.
The ECM performs electrical integrity checks on the CVS valve to determine wiring or power supply faults. The ECM
can also detect a valve blockage if the signal from the fuel tank pressure sensor indicates a depressurising fuel tank
while the CVS valve should be open to atmosphere.

EMISSION CONTROL - V8
17-2-24 DESCRIPTION AND OPERATION
Leak Detection Pump (NAS vehicles with positive pressure EVAP system leakage test only)
1Harness connector
2Leak detection pump motor
3Atmosphere connection to/from EVAP canister
4Atmosphere connection to/from air filter
5Leak detection pump solenoid valve
The fuel evaporation leak detection pump is mounted forward of the EVAP canister on a bracket fitted beneath the
vehicle on the RH side of the vehicle chassis. The leak detection pump is fixed to the bracket by three screws through
the bottom of the bracket.
A short hose connects between the atmosphere vent port of the EVAP canister and a port at the rear of the fuel
evaporation leak detection pump. The hose is secured to the ports at each end by crimped metal band clips.
An elbowed quick fit connector on the top of the fuel evaporation leak detection pump connects to atmosphere via a
large bore pipe. The pipe is routed along the underside of the vehicle chassis and up into the RH side of the engine
compartment where it connects to an air filter canister.
The leak detection pump incorporates a 3–pin electrical connector. Pin-1 is the earth switched supply to the ECM for
control of the pump solenoid valve. Pin-2 is the earth switched supply to the ECM for the operation of the pump motor.
Pin-3 is the power supply to the pump motor and solenoid valve and is switched on at system start up via the main
relay and fuse 2 in the engine compartment fusebox.
Under normal circumstances (i.e. when the leak detection pump is not operating and the solenoid is not energised),
the EVAP canister vent port is connected to atmosphere via the open solenoid valve.
The pump is operated at the end of a drive cycle when the vehicle is stationary and the ignition is switched off.
M17 0213
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EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-25
The leak detection pump module contains an integral air by-pass circuit with restrictor (reference-leak orifice) which
is used for providing a reference value for the leak detection test. The restrictor corresponds to an air leak equivalent
to 0.5 mm (0.02 in) diameter. With the solenoid valve open and the purge valve closed, the pump forces pressurised
air through the orifice while the current drawn by the leak detection pump motor is monitored to obtain the reference
value. The orifice must be kept free from contamination, otherwise the reference restriction may appear less than for
a 0.5 mm leak and consequently adversely affect the diagnostic results.
During the leakage test, the solenoid valve is energised, closing the atmosphere vent line between the EVAP canister
and atmosphere and opening a path to the pressurised air supplied from the leak detection pump motor. Air is pumped
into the EVAP system, while the current drawn by the pump motor is monitored. The current drawn during the leakage
test is compared against the value obtained during the reference check, to determine if an EVAP system leak is
present.
The fuel leak detection pump is powered from a 12V supply and operates at a working pressure of 3 kPa.
Air filter – (NAS vehicles with positive pressure leak detection system only)
1Air vents through canister lid
2Air filter canister
3To fuel leak detection pump (EVAP canister
atmosphere vent)
A paper element air filter (40
µm) is located in a plastic canister at the RH side of the engine compartment. The air
filter canister is fixed to the cruise control mounting bracket by a single nut and bolt. A large bore plastic pipe is
connected to a port at the base of the air filter canister and is secured to the port by a short nylon hose and two crimped
metal band clips.
The air filter is used to prevent particulate contaminants down to 40
µm from entering the fuel leak detection pump.
A press-fit lid on top of the canister contains slots to allow the passage of air into and out of the EVAP system.
The bottom end of the paper element is sealed to the canister and is non-serviceable (i.e fit for life). If necessary, the
canister and paper filter must be replaced as a single, complete assembly.
M17 0203
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EMISSION CONTROL - V8
17-2-26 DESCRIPTION AND OPERATION
Secondary air injection system
The secondary air injection (SAI) system comprises the following components:
lSecondary air injection pump
lSAI vacuum solenoid valve
lSAI control valves (2 off, 1 for each bank of cylinders)
lSAI pump relay
lVacuum reservoir
lVacuum harness and pipes
The secondary air injection system is used to limit the emission of carbon monoxide (CO) and hydrocarbons (HCs)
that are prevalent in the exhaust during cold starting of a spark ignition engine. The concentration of hydrocarbons
experienced during cold starting at low temperatures are particularly high until the engine and catalytic converter
reach normal operating temperature. The lower the cold start temperature, the greater the prevalence of
hydrocarbons emitted from the engine.
There are several reasons for the increase of HC emissions at low cold start temperatures, including the tendency for
fuel to be deposited on the cylinder walls, which is then displaced during the piston cycle and expunged during the
exhaust stroke. As the engine warms up through operation, the cylinder walls no longer retain a film of fuel and most
of the hydrocarbons will be burnt off during the combustion process.
The SAI pump is used to provide a supply of air into the exhaust ports in the cylinder head, onto the back of the
exhaust valves, during the cold start period. The hot unburnt fuel particles leaving the combustion chamber mix with
the air injected into the exhaust ports and immediately combust. This subsequent combustion of the unburnt and
partially burnt CO and HC particles help to reduce the emission of these pollutants from the exhaust system. The
additional heat generated in the exhaust manifold also provides rapid heating of the exhaust system catalytic
converters. The additional oxygen which is delivered to the catalytic converters also generate an exothermic reaction
which causes the catalytic converters to 'light off' quickly.
The catalytic converters only start to provide effective treatment of emission pollutants when they reach an operating
temperature of approximately 250
°C (482°F) and need to be between temperatures of 400°C (752°F) and 800°C
(1472
°F) for optimum efficiency. Consequently, the heat produced by the secondary air injection “afterburning”,
reduces the time delay before the catalysts reach an efficient operating temperature.
The engine control module (ECM) checks the engine coolant temperature when the engine is started, and if it is below
60º C (131
°F), the SAI pump is started. Secondary air injection will remain operational for a period controlled by the
ECM (76 seconds for NAS vehicles, 64 seconds for EU-3 vehicles). The SAI pump operation can be cut short due to
excessive engine speed or load.
Air from the SAI pump is supplied to the SAI control valves via pipework and an intermediate T-piece which splits the
air flow evenly to each bank.
At the same time the secondary air pump is started, the ECM operates a SAI vacuum solenoid valve, which opens to
allow vacuum from the reservoir to be applied to the vacuum operated SAI control valves on each side of the engine.
When the vacuum is applied to the SAI control valves, they open simultaneously to allow the air from the SAI pump
through to the exhaust ports. Secondary air is injected into the inner most exhaust ports on each bank.
When the ECM breaks the ground circuit to de-energise the SAI vacuum solenoid valve, the vacuum supply to the
SAI control valves is cut off and the valves close to prevent further air being injected into the exhaust manifold. At the
same time as the SAI vacuum solenoid valve is closed, the ECM opens the ground circuit to the SAI pump relay, to
stop the SAI pump.
A vacuum reservoir is included in the vacuum line between the intake manifold and the SAI vacuum solenoid valve.
This prevents changes in vacuum pressure from the intake manifold being passed on to cause fluctuations of the
secondary air injection solenoid valve. The vacuum reservoir contains a one way valve and ensures a constant
vacuum is available for the SAI vacuum solenoid valve operation. This is particularly important when the vehicle is at
high altitude.

EMISSION CONTROL - V8
17-2-28 DESCRIPTION AND OPERATION
The SAI pump is attached to a bracket at the rear RH side of the engine compartment and is fixed to the bracket by
three studs and nuts. The pump is electrically powered from a 12V battery supply via a dedicated relay and supplies
approximately 35kg/hr of air when the vehicle is at idle in Neutral/Park on a start from 20
°C (68°F).
Air is drawn into the pump through vents in its front cover and is then passed through a foam filter to remove
particulates before air injection. The air is delivered to the exhaust manifold on each side of the engine through a
combination of plastic and metal pipes.
The air delivery pipe is a flexible plastic type, and is connected to the air pump outlet via a plastic quick-fit connector.
The other end of the flexible plastic pipe connects to the fixed metal pipework via a short rubber hose. The part of the
flexible plastic pipe which is most vulnerable to engine generated heat is protected by heat reflective sleeving. The
metal delivery pipe has a fabricated T-piece included where the pressurised air is split for delivery to each exhaust
manifold via the SAI control valves.
The pipes from the T-piece to each of the SAI control valves are approximately the same length, so that the pressure
and mass of the air delivered to each bank will be equal. The ends of the pipes are connected to the inlet port of each
SAI control valve through short rubber hose connections.
The T-piece is mounted at the rear of the engine (by the ignition coils) and features a welded mounting bracket which
is fixed to the engine by two studs and nuts.
The foam filter in the air intake of the SAI pump provides noise reduction and protects the pump from damage due to
particulate contamination. In addition, the pump is fitted on rubber mountings to help prevent noise which is generated
by pump operation from being transmitted through the vehicle body into the passenger compartment.
If the secondary air injection pump malfunctions, the following fault codes may be stored in the ECM diagnostic
memory, which can be retrieved using 'Testbook':
Secondary air injection (SAI) pump relay
The secondary air injection pump relay is located in the engine compartment fusebox. The engine control module
(ECM) is used to control the operation of the SAI pump via the SAI pump relay. Power to the coil of the relay is supplied
from the vehicle battery via the main relay and the ground connection to the coil is via the ECM.
Power to the SAI pump relay contacts is via fusible link FL2 which is located in the engine compartment fusebox.
P-code Description
P0418Secondary air injection pump powerstage fault (e.g. - SAI pump relay fault / SAI
pump or relay not connected / open circuit / harness damage).

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-29
Secondary air injection (SAI) vacuum solenoid valve
1Vacuum port to intake manifold (via vacuum
reservoir)
2SAI vacuum solenoid valve
3Electrical connector
4Vacuum port to vacuum operated SAI control
valves5Purge valve clip
6Mounting bracket
The SAI vacuum solenoid valve is located at the rear LH side of the engine and is electrically operated under the
control of the ECM. The SAI vacuum solenoid valve is mounted on a bracket together with the EVAP system purge
valve.
Vacuum to the SAI vacuum solenoid valve is provided from the intake manifold depression via a vacuum reservoir. A
small bore vacuum hose with rubber elbow connections at each end provides the vacuum route between the vacuum
reservoir and SAI vacuum solenoid valve. A further small bore vacuum hose with a larger size elbow connector is
used to connect the SAI vacuum solenoid valve to the SAI control valves on each side of the engine via an
intermediate connection. The SAI vacuum solenoid valve port to the SAI control valves is located at a right angle to
the port to the vacuum reservoir.
The intermediate connection in the vacuum supply line is used to split the vacuum equally between the two SAI control
valves. The vacuum hose intermediate connection is located midpoint in front of the inlet manifold. All vacuum hose
lines are protected by flexible plastic sleeving.
M17 0211
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