1999 LAND ROVER DEFENDER light

ENGINE MANAGEMENT SYSTEM
7
DESCRIPTION AND OPERATION SENSOR - MASS AIR FLOW (MAF)
The MAF sensor is located in the intake system between the air filter housing and the turbocharger. The ECM
uses the information generated by the MAF sensor to control exhaust gas recirculation (EGR).
The MAF sensor works on the hot film principal. The MAF sensor has 2 sensing elements contained within a film.
One element is controlled at ambient temperature e.g. 25°C (77°F) while the other is heated to 200°C (360°F)
above this temperature e.g. 225°C (437°F). As air passes through the MAF sensor the hot film will be cooled.
The current required to keep the constant 200°C (360°F) difference provides a precise although non-linear signal
of the air drawn into the engine. The MAF sensor sends a voltage of between 0 and 5 volts to the ECM,
proportional to the mass of the incoming air. This calculation allows the ECM to set the EGR ratio for varying
operating conditions.
Inputs / Outputs
The MAF sensor receives battery voltage (C0149-3) via the ECM on a brown/orange wire. Signal output on a
slate/light green wire from the MAF sensor (C0149-2) to the ECM (C0158-11) is a variable voltage proportional to
the air drawn into the engine. The MAF sensor is provided an earth (C0149-1) via the ECM (C0158-20) on a
pink/black wire.
The MAF sensor can fail or supply an incorrect signal if one or more of the following occurs:
Sensor open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Contaminated sensor element.
Damaged sensor element.
Damaged wiring harness.
MAF sensor supplies incorrect signal (due to air leak or air inlet restriction).
In the event of a MAF sensor signal failure any of the following symptoms my be observed:
During driving, engine speed may dip before recovering.
Difficult starting.
Engine stalls after starting.
Delayed throttle response.
EGR inoperative.
Reduced engine performance.
MAF signal out of parameters.
In the event of a MAF sensor failure, the ECM will use a fixed default value from its memory.
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ENGINE MANAGEMENT SYSTEM
23
DESCRIPTION AND OPERATION MODULATOR - EXHAUST GAS REGULATOR (EGR)
The EGR modulator is located on the RH side inner front wing. It regulates the vacuum source to the EGR valve
allowing it to open or close. The ECM utilises the EGR modulator to control the amount of exhaust gas being
recirculated in order to reduce exhaust emissions and combustion noise. Optimum EGR is usually obtained when
the vehicle is operating at light throttle openings, and the vehicle is cruising at approximately 2000 to 3000
rev/min.
Input / Output
The EGR modulator (C0191-1) receives a feed from the main relay (C0063-87) on a brown/orange wire via header
294. The earth path for the modulator (C0191-2) is controlled by the ECM (C0158-3) on a blue wire. The length of
time the ECM supplies an earth is how long the exhaust gases are allowed to recirculate. The ECM decides how
long to supply the earth by looking at engine temperature and engine load.
The EGR modulator can fail in one or more of the following ways:
Solenoid open circuit.
Short circuit to vehicle supply.
Short circuit to earth.
In the event of an EGR modulator failure, the EGR system will become inoperative.
WARNING LAMP - GLOW PLUG
The glow plug warning lamp is located in the instrument pack. It illuminates to alert the driver that the glow plugs
are being heated prior to the engine being started. The length of time that the lamp illuminates and the glow plugs
are operating prior to cranking is the pre-heat period. The length of time of this period is determined by the ECT
sensor signal, controlled by the ECM.
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26COOLING SYSTEM
6
DESCRIPTION AND OPERATION By-pass flow valve
The by-pass flow valve is held closed by a light spring. It operates to further aid heater warm-up. When the main
valve is closed and the engine speed is below 1500 rev/min, the coolant pump does not produce sufficient flow
and pressure to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit
and forces the coolant through the heater matrix only. This provides a higher flow of warm coolant through the
heater matrix to improve passenger comfort in cold conditions.
When the engine speed increases above 1500 rev/min the coolant pump produces a greater flow and pressure
than the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure,
opening the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant
flow through the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the
engines cooling needs at higher engine rev/min.
Outlet Housing
A cast aluminium outlet housing is attached to the cylinder head with three bolts and sealed with a gasket. Coolant
leaves the engine through the outlet housing and is directed through a hose to the heater matrix, the radiator or
the by-pass circuit.
An Engine Coolant Temperature (ECT) sensor is installed in a threaded port on the side of the outlet housing. The
sensor monitors coolant temperature emerging from the engine and sends signals to the Engine Control Module
(ECM) for engine management and temperature gauge operation.
Expansion Tank
The expansion tank is located in the engine compartment. The tank is made from moulded plastic and attached to
brackets on the right hand inner wing. A maximum coolant when cold level is moulded onto the tank.
Excess coolant created by heat expansion is returned to the expansion tank from the radiator bleed pipe at the top
of the radiator. An outlet pipe is connected into the coolant pump feed hose and replaces the coolant displaced by
heat expansion into the system when the engine is cool.
The expansion tank is fitted with a sealed pressure cap. The cap contains a pressure relief valve which opens to
allow excessive pressure and coolant to vent through the overflow pipe. The relief valve is open at a pressure of
1.4 bar (20 lbf.in) and above.
Heater Matrix
The heater matrix is fitted in the heater assembly inside the passenger compartment. Two pipes pass through the
bulkhead into the engine compartment and provide coolant flow to and from the matrix. The pipes from the
bulkhead are connected to the matrix, sealed with’O’rings and clamped with circular rings.
The matrix is constructed from aluminium with two end tanks interconnected with tubes. Aluminium fins are
located between the tubes and conduct heat from the hot coolant flowing through the tubes. Air from the heater
assembly is warmed as it passes through the matrix fins. The warm air is then distributed in to the passenger
compartment as required.
When the engine is running, coolant from the engine is constantly circulated through the heater matrix.
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COOLING SYSTEM
11
DESCRIPTION AND OPERATION OPERATION
Coolant Flow - Engine Warm Up
During warm up the coolant pump moves fluid through the cylinder block and it emerges from the outlet housing.
From the outlet housing, the warm coolant flow is prevented from flowing through the upper and lower radiators
because both thermostats are closed. The coolant is directed into the heater circuit.
Some coolant from the by-pass pipe can pass through small sensing holes in the flow valve. The warm coolant
enters a tube in the thermostat housing and surrounds 90% of the thermostat sensitive area. Cold coolant
returning from the radiator bottom hose conducts through 10% of the thermostat sensitive area. In cold ambient
temperatures the engine temperature can be raised by up to 10°C (50°F) to compensate for the heat loss of the
10% exposure to the cold coolant return from the radiator bottom hose.
At engine speeds below 1500 rev/min, the by-pass valve is closed only allowing the small flow through the sensing
holes. As the engine speed increases above 1500 rev/min, the greater flow and pressure from pump overcomes
the light spring and opens the by-pass flow valve. The flow valve opens to meet the engine’s cooling needs at
higher engine speeds and prevents excess pressure in the cooling system. With both thermostats closed,
maximum flow is directed through the heater circuit.
The heater matrix acts as a heat exchanger reducing the coolant temperature as it passes through the matrix.
Coolant emerges from the heater matrix and flows to the fuel cooler’T’connection via the heater return hose.
From the fuel cooler the coolant is directed into the coolant pump feed pipe and recirculated around the heater
circuit. In this condition the cooling system is operating at maximum heater performance.
Coolant Flow - Engine Hot
As the coolant temperature increases the main thermostat opens. This allows some coolant from the outlet
housing to flow through the top hose and into the radiator to be cooled. The hot coolant flows from the left tank in
the radiator, along the tubes to the right tank. The air flowing through the fins between the tubes cools the coolant
as it passes through the radiator.
A controlled flow of the lower temperature coolant is drawn by the pump and blended with hot coolant from the
by-pass and the heater return pipes in the pump feed pipe. The pump then passes this coolant, via the cylinder
block, to the oil cooler housing, cooling the engine oil before entering the block to cool the cylinders.
When the fuel temperature increases, the heat from the fuel conducts through the fuel cooler’T’connection and
causes the fuel thermostat to open. Coolant from the cylinder block flows through the oil cooler and via a pipe and
hose enters the lower radiator. The lower temperature coolant from the oil cooler housing is subjected to an
additional two passes through the lower radiator to further reduce the coolant temperature. From the lower radiator
the coolant flows , via a hose, to the fuel cooler.
As the hot fuel cools, travelling slowly forwards through the cooler, it meets the progressively colder coolant
travelling in the opposite direction from the lower radiator.
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37 - MANUAL GEARBOX
CONTENTS
Page
ADJUSTMENT
SPRINGS - GEAR LEVER BIAS 1..........................................................................
GEARBOX OIL - DRAIN AND REFILL 2.................................................................
REPAIR
COVER - FRONT - RESEAL AND FIT NEW INPUT SHAFT OIL SEAL 1..............
LEVER - GEAR CHANGE 3....................................................................................
MECHANISM AND HOUSING - GEAR SELECTOR 4...........................................
MECHANISM AND HOUSING - GEAR SELECTOR - RESEAL 6..........................
GEARBOX 7...........................................................................................................
SWITCH - REVERSE LIGHT 12.............................................................................
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MANUAL GEARBOX
1
ADJUSTMENT SPRINGS - GEAR LEVER BIAS
Service repair no - 37.16.26
Check
NOTE: The purpose of this adjustment is
to set both bolts so that the bias spring
legs apply equal pressure on both ends of
the gear lever cross pin when 3rd or 4th gear is
engaged. This will ensure that when the gear lever
is in neutral, the gear change mechanism is
automatically aligned for 3rd or 4th gears.
1.Remove gear lever knobs.
2.Release and remove gear lever gaiter.
3.Select 3rd or 4th gear.
4.Adjust the two adjusting screws until both legs of
the spring are approximately 0.5 mm (0.02 in)
clear of cross pin in the gear lever.
5.Apply a light load to the gear lever in a RH
direction and adjust the LH adjusting screw
downwards until the LH spring leg just makes
contact with the cross pin.
6.Repeat the same procedure for the RH adjusting
screw.
7.Lower both adjusting screws equal amounts until
the radial play is just eliminated. Tighten lock
nuts.
8.Return gear lever to neutral position and move
gear lever across the gate several times. The
gear lever should return to the 3rd and 4th gate.
9.Fit gear lever gaiter.
10.Fit gear lever knobs.
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37MANUAL GEARBOX
10
REPAIR
34.Pull handbrake cable through heel board.
35.Disconnect multiplug from speed sensor and
release harness from clip on transfer gearbox.
36.Remove retaining nut and release battery earth
lead from transfer gearbox.
37.Release body harness clips from bracket on top
of transfer gearbox.
38.Lower gearbox jack sufficiently to allow transfer
gearbox lever to clear tunnel.
39.Disconnect 2 Lucars from differential lock switch,
multiplug from reverse light switch and multiplug
from low ratio detect switch - if fitted and release
multiplug from bracket.
40.Remove bolt and release earth leads from RH
side of transfer gearbox.
41.Support the weight of the engine.
42.Remove 6 bolts securing clutch housing to
engine.
43.With assistance, remove gearbox from engine.
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MANUAL GEARBOX
11
REPAIR Refit
44.Clean gearbox to engine mating faces, dowels
and dowel holes.
45.With assistance raise gearbox on jack and align
to clutch and engine.
46.Fit lower bolts securing clutch housing to engine
and tighten to50 Nm (37 lbf.ft).
NOTE: Do not fit upper bolts at this stage.
47.Fit earth leads and secure with bolt.
48.Connect Lucars to differential lock switch,
multiplug to reverse light switch, position
multiplug to bracket and connect low ratio detect
multiplug - if fitted.
49.Raise gearbox jack and guide transfer gearbox
lever through tunnel.
50.Secure body harness clips to bracket on top of
transfer gearbox.
51.Position battery earth lead to transfer gearbox
and tighten retaining nut.
52.Connect multiplug to speed sensor and secure
harness in clip on transfer gearbox.
53.Position mounting brackets and rubber
mountings, positioning heat shield to LH
mounting and tighten bracket bolts to85 Nm (63
lbf.ft).
54.Position nuts to mountings and tighten to48 Nm
(35 lbf.ft).
55.Remove 3 bolts securing support plate
LRT-99-007to gearbox.
56.Position handbrake cable through heel board.
57.Position clutch slave cylinder, fit bolts and
tighten to25 Nm (18 lbf.ft).
58.Clean propeller shafts and mating faces.
59.Position propeller shafts, align to marks and
tighten nuts to48 Nm (35 lbf.ft).
60.Clean intermediate silencer and tail pipe mating
faces.
61.Position silencer and secure on mountings,
using a new gasket align to tail pipe, fit nuts and
tighten to25 Nm (18 lbf.ft).
62.Refill gearbox with oil.See Adjustment.
63.Refill transfer gearbox with oil.See
MAINTENANCE ,
64.Fit exhaust front pipe.See MANIFOLD AND
EXHAUST SYSTEM, Repair.
65.Refit starter motor.See ELECTRICAL, Repair.
66.Fit bolt securing shim plate to clutch housing and
tighten10 Nm (7 lbf.ft).
67.Position heater pipe to gearbox housing, fit
upper bolts securing clutch housing to engine
and tighten to50 Nm (37 lbf.ft).
68.Position gearbox breather pipes to clips on
heater hose.69.Fit air cleaner.See FUEL SYSTEM, Repair.
70.Fit cooling fan.See COOLING SYSTEM,
Repair.
71.Fit and align tunnel cover, fit and tighten screws.
72.Position relay panel, fit spacers and tighten
screws.
73.Position hand-brake lever and tighten bolts to25
Nm (18 lbf.ft).
74.Connect handbrake cable to lever, fit clevis pin,
washer and new split pin.
75.Connect Lucar to hand-brake switch.
76.Position gaiter to handbrake lever and secure
with trim stud.
77.Locate insulation pad over gear levers and fit to
tunnel cover.
78.Align spline marks, fit gear lever to lower lever,
fit washer and secure with retaining nut.
79.Position gear lever cover.
80.Position gearbox tunnel carpet.
81.Fit gear lever and transfer gear lever knobs.
82.Reconnect battery negative lead.
83.Fit battery cover.
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