1999 LAND ROVER DISCOVERY fuel filter

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-25
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 canister3To 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
17-2-38 DESCRIPTION AND OPERATION
Mass Air Flow (MAF) Sensor and Air Temperature Sensor
The engine management ECM uses the mass air flow sensor to measure the mass of air entering the intake and
interprets the data to determine the precise fuel quantity which needs to be injected to maintain the stoichiometric
air:fuel ratio for the exhaust catalysts. If the mass air flow sensor fails, lambda control and idle speed control will be
affected and the emission levels will not be maintained at the optimum level. If the device should fail and the ECM
detects a fault, it invokes a software backup strategy.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
The air temperature sensor is used by the engine management ECM to monitor the temperature of the inlet air. If the
device fails, catalyst monitoring will be affected. The air temperature sensor in integral to the mass air flow sensor.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
Throttle Position Sensor
If the engine management ECM detects a throttle position sensor failure, it may indicate a blocked or restricted air
intake filter. Failure symptoms may include:
lPoor engine running and throttle response
lEmission control failure
lNo closed loop idle speed control
lAltitude adaption is incorrect
If a signal failure should occur, a default value is derived using data from the engine load and speed.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
Atmospheric pressure will vary with altitude and have a resulting influence on the calculations performed by the ECM
in determining the optimum engine operating conditions to minimise emissions. The following are approximate
atmospheric pressures for the corresponding altitudes:
l0.96 bar at sea level
l0.70 bar at 2,750 m (9,000 ft.)

EMISSION CONTROL - V8
17-2-42 DESCRIPTION AND OPERATION
If the piping is broken forward of the purge valve or is not connected, the engine may run rough and fuelling adaptions
will drift. The fault will not be detected by the leak detection diagnostic, but it will be determined by the engine
management ECM through the fuelling adaption diagnostics.
The evaluation of leakage is dependent on the differential pressure between the fuel tank and ambient atmospheric
pressure, the diagnostic is disabled above altitudes of 9500 ft. (2800 m) to avoid false detection of fuel leaks due to
the change in atmospheric pressure at altitude.
Fuel Leak Detection System Operation (positive pressure leak detection type) – NAS only
The EVAP system with positive pressure leak detection capability used on NAS vehicles is similar to the standard
system, but also includes a fuel evaporation leak detection pump with integral solenoid valve. It is capable of detecting
holes in the EVAP system down to 0.5 mm (0.02 in.). The test is carried out at the end of a drive cycle, when the
vehicle is stationary and the ignition switch has been turned off. The ECM maintains an earth supply to the Main relay
to hold it on, so that power can be supplied to the leak detection pump.
First a reference measurement is established by passing the pressurised air through a by-pass circuit containing a
fixed sized restriction. The restriction assimilates a 0.5 mm (0.02 in) hole and the current drawn by the pump motor
during this procedure is recorded for comparison against the value to be obtained in the system test. The purge valve
is held closed, and the reversing valve in the leak detection pump module is not energised while the leak detection
pump is switched on. The pressurised air from the leak detection pump is forced through an orifice while the current
drawn by the pump motor is monitored.
Next the EVAP system diagnostic is performed; the solenoid valve is energised so that it closes off the EVAP system's
vent line to atmosphere, and opens a path for the pressurised air from the leak detection pump to be applied to the
closed EVAP system.
The current drawn by the leak detection pump is monitored and checked against that obtained during the reference
measurement. If the current is less than the reference value, this infers there is a hole in the EVAP system greater
than 0.5 mm (0.02 in) which is allowing the positive air pressure to leak out. If the current drawn by the pump motor
is greater than the value obtained during the reference check, the system is sealed and free from leaks. If an EVAP
system leak is detected, the ECM stores the fault in diagnostic memory and the MIL light on the instrument pack is
illuminated.
On NAS vehicles, the ECM works on a 2 trip cycle before illuminating the MIL. On EU-3 vehicles, the ECM works on
a 3 trip cycle before illuminating the MIL.
Following the test, the solenoid valve is opened to normalise the EVAP system pressure and the system returns to
normal purge operation at the start of the next drive cycle. Possible reasons for an EVAP system leak test failure are
listed below:
lFuel filler not tightened or cap missing.
lSensor or actuator open circuit.
lShort circuit to vehicle supply or ground.
lEither purge or solenoid valve stuck open.
lEither purge or solenoid valve stuck shut.
lBlocked pipe or air filter.
lPiping broken or not connected.
lLoose or leaking connection.
If the piping is broken forward of the purge valve or is not connected, the engine may run rough and fuelling adaptions
will drift. The fault will not be detected by the leak detection test, but will be determined by the engine management
ECM through the fuelling adaption diagnostics. This test can be run from TestBook/T4.

EMISSION CONTROL - V8
REPAIRS 17-2-53
Canister - EVAP - Models with Fuel Leak
Detection Pump - from 03MY
$% 17.15.13
Remove
1.Raise the vehicle on lift.
2.Disconnect multiplug from the fuel leak
detection pump.
3.Disconnect the fuel leak detection filter pipe
from the fuel leak detection pump.
4.Release clips and disconnect 2 vent pipes from
the EVAP canister.
CAUTION: Always fit plugs to open
connections to prevent contamination.5.Remove and discard 4 bolts securing EVAP
canister mounting bracket to the chassis and
remove the EVAP canister assembly.
NOTE: Do not carry out further dismantling if
component is removed for access only.
6.Remove bolt securing EVAP canister retaining
clamp to the mounting bracket and collect the
clamp.
7.Remove nut and bolt securing EVAP canister to
the mounting bracket.

EMISSION CONTROL - V8
17-2-54 REPAIRS
8.Remove and discard clip securing fuel leak
detection pump fuel pipe to the EVAP canister
and disconnect the fuel pipe.
9.Remove the EVAP canister.
Refit
1.Position EVAP canister to the mounting
bracket.
2.Connect fuel leak detection pump fuel pipe to
the EVAP canister and secure with a new clip.
3.Fit nut and bolt securing EVAP canister to the
mounting bracket and tighten to 10 Nm (7 lbf.ft).
4.Position EVAP canister retaining clamp to the
mounting bracket, fit bolt and tighten to 10 Nm
(7 lbf.ft).
5.Position EVAP canister mounting bracket to the
chassis, fit new bolts and tighten to 25 Nm (18
lbf.ft).
6.Connect vent pipes to the EVAP canister.
7.Connect multiplug to the fuel leak detection
pump.
8.Connect the fuel leak detection filter pipe to the
fuel leak detection pump.
9.Lower the vehicle lift.
Valve - purge control
$% 17.15.39
Remove
1.Disconnect multiplug from purge control valve.
2.Release clips securing hoses to purge control
valve.
3.Disconnect hoses from purge control valve and
remove valve.
CAUTION: Always fit plugs to open
connections to prevent contamination.
Refit
1.Position purge control valve and connect
hoses.
2.Fit clips to secure hoses to purge control valve.
3.Connect multiplug to purge control valve.

EMISSION CONTROL - V8
17-2-64 REPAIRS
Pump - Fuel Leak Detection - up to 03MY
$% 17.45.41
Remove
1.Raise the vehicle on lift.
2.Disconnect multiplug from fuel leak detection
pump.
3.Release leak detection air filter hose from top of
pump.
4.Remove 3 Torx screws securing pump to
mounting bracket.
5.Remove clip securing EVAP canister hose to
pump.
6.Release EVAP canister hose from pump.
7.Remove pump.
Refit
1.Connect EVAP canister hose to pump and
secure with clip.
2.Position pump to mounting bracket and secure
with Torx screws.
3.Connect leak detection air filter hose to top of
leak detection pump.
4.Connect multiplug to pump.
5.Lower vehicle.
Pump - fuel leak detection - from 03MY
$% 17.45.41
Remove
1.Raise the vehicle on lift.
2.Disconnect multiplug from the fuel leak
detection pump.
3.Remove 3 screws securing the fuel leak
detection pump to the chassis mounting
bracket.
4.Position absorbent cloth around fuel hoses to
collect any fuel spillage.
5.Disconnect the fuel leak detection filter pipe
from the fuel leak detection pump.
CAUTION: Always fit plugs to open
connections to prevent contamination.
6.Remove and discard clip securing EVAP pipe
to the fuel leak detection pump and disconnect
the pipe.
7.Remove the fuel leak detection pump.
Refit
1.Connect the EVAP pipe to the fuel leak
detection pump and secure with a new clip.
2.Connect the fuel leak detection filter pipe to the
fuel leak detection pump.
3.Remove absorbent cloth.
4.Fit and tighten 3 screws securing the fuel leak
detection pump to the chassis mounting
bracket.
5.Connect multiplug to the fuel leak detection
pump.
6.Lower the vehicle lift.
M17 0235
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EMISSION CONTROL - V8
REPAIRS 17-2-65
Filter - fuel leak detection pump - up to
03MY
$% 17.45.42
Remove
1.Remove bolt securing air filter to mounting
bracket and collect nut.
2.Remove clip securing hose to air filter.
3.Release hose from air filter.
4.Remove air filter.
Refit
1.Connect hose to air filter and secure with clip.
2.Position air filter to mounting bracket and
secure with nut and bolt.
Filter - fuel leak detection pump - from
03MY
$% 17.45.42
Remove
1.Remove Allen bolt securing fuel leak detection
pump filter to the mounting bracket.
2.Remove and discard clip securing fuel pipe to
the fuel leak detection pump filter and
disconnect the pipe.
CAUTION: Always fit plugs to open
connections to prevent contamination.
3.Remove the fuel leak detection pump filter.
Refit
1.Connect fuel pipe to the fuel leak detection
pump and secure with a new clip.
2.Position fuel leak detection pump filter to
mounting bracket, fit Allen bolt and tighten to 3
Nm (2.2 lbf.ft).
17M 0224

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-27
There are two types of IAT sensor diagnostic checks:
lThe IAT sensor signal is less than the minimum threshold – the engine has to have been running for longer than
180 seconds, and idle speed control must have been operational for longer than 10 seconds. No fuel cut off is
active. The IAT sensor signal must be less than -35°C (-31°F) for longer than 200 ms.
lThe IAT sensor signal is greater than the maximum threshold – the ECM has to be powered up (engine does not
need to be running), and the signal must be greater than 140°C (284°F) for longer than 200 ms.
If the IAT sensor fails the following fault codes will be produced and can be retrieved by TestBook:
Air intake duct – Gulf models from 2000MY
1Heat reflective insulation2Supplementary air intake duct
The density of the intake air is partly dependent on altitude and temperature. Hot air has a lower density than cold air;
consequently in hot climates, the low air density can result in low power due to low volumetric efficiency.
In order to improve engine performance, Gulf specification models from 2000MY have a secondary air intake duct
which is located under the front left inner wing of the vehicle. Cooler air from the side of the vehicle is routed through
the duct to the air cleaner, where it combines with air entering via the front grille.
In addition to the secondary air duct, the vehicles are fitted with a larger front grille and have larger cooling and
condenser fans.
The MAF/IAT sensor, air cleaner and air cleaner duct are encased in insulation bags to help keep the intake air cool
and so increase the mass of air entering the engine intake manifold.
The air cleaner includes a cyclone filter and also a dump valve in the bottom of the unit. Sand and dust particles which
are carried into the air cleaner with the air flow are automatically expunged via the dump valve.
P code J2012 description Land Rover description
P0112 Intake air temperature circuit low input Intake air temperature signal less than minimum
threshold, after time for exhaust to warm up
P0113 Intake air temperature circuit high input Intake air temperature signal greater than maximum
threshold
M180452
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