ignition LAND ROVER DISCOVERY 1999 Repair Manual

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-67
SET+/RES switches
The cruise control system uses two steering wheel switches labelled SET+ and RES.
The SET+ switch performs the set speed, tap up and accelerator functions. The RES switch performs the resume and
suspend functions.
With the cruise control master switch on and the vehicle in the cruise control operating speed range, one press of the
SET+ switch stores a speed value in the cruise control ECU. If the switch is pressed and held while the vehicle is
under cruise control operation, speed increases until the switch is released. At this point the cruise control ECU stores
the new speed value. If the switch is tapped (held down for less than 0.5 second) the cruise control ECU increases
vehicle speed by 1 mph (1.5 km/h).
If the RES switch is pressed while the systems is inactive (no stored values) the system will not respond. If there is
a stored value in the cruise control ECU memory and the switch is pressed, the cruise control system operates and
holds the vehicle at the stored road speed. If the cruise control system is active and the RES switch is depressed,
the cruise control ECU deactivates cruise operation but maintains the current set speed value.
Input/Output
The input from the SET+ switch to the cruise control ECU is either 12 Volts or an open circuit.
The input from the RES switch to the cruise control ECU is either 12 Volts or an open circuit.
The following diagnostic information is available through TestBook:
lThe state of operator switch SET+.
lThe state of operator switch RES.
ECU operating parameters (connector connected)
Pin No. Condition Volts Ohms
4 Ignition in position II, SET+ switch
releasedMore than 10,000
4 Ignition in position II, SET+ switch
pressed12
2 Ignition in position II, RES switch
releasedMore than 10,000
2 Ignition in position II, RES switch
pressed12

ENGINE MANAGEMENT SYSTEM - V8
18-2-68 DESCRIPTION AND OPERATION
Brake pedal switch
The cruise control ECU has two inputs from the brake pedal switch that determine the position of the brake pedal.
One input comes through the BCU and is low when the brake pedal is not pressed. The second input comes directly
from the brake pedal switch. This input is high when the brake pedal is not pressed. On vehicles with a manual
gearbox, the input from the clutch pedal switch to the cruise control ECU is connected in series with the direct signal
from the brake pedal switch.
If the cruise control ECU receives a changed signal from either source, it deactivates cruise control, removing power
to the vacuum pump and activating the vacuum control valve releasing all vacuum in the system.
The brake pedal switch also provides the signal to illuminate the brake lamps and the brake input to the SLABS ECU.
Input/Output
With the brake pedal and the clutch pedal in the rest position, the cruise control ECU receives 12 Volts.
With the brake pedal pressed, the cruise control ECU receives 0 Volts and a low voltage logic signal from the BCU.
NOTE: If the clutch pedal is pressed, 0 Volts are present at the cruise control ECU irrespective of brake pedal position.
ECU operating parameters (connector connected)
Pin No. Condition Volts Ohms
1 Ignition in position II, brake pedal
released, clutch pedal released12
1 Ignition in position II, brake pedal
pressed, clutch pedal releasedMore than 10,000
1 Ignition in position II, brake pedal
released, clutch pedal pressedMore than 10,000

ENGINE MANAGEMENT SYSTEM - V8
18-2-74 DESCRIPTION AND OPERATION
Operation - cruise control
Cruise control activation
Cruise control is a passive system. The driver must activate it. Switching on the cruise control master switch located
on the instrument panel activates cruise control. An LED in the switch illuminates, indicating cruise control is
available. The driver must accelerate the vehicle to the desired speed using the accelerator pedal. When the desired
speed is reached, pressing the SET+ switch activates cruise control. Cruise control will only activate if the following
conditions are met:
lVehicle speed is between 28 - 125 mph (45 - 200 km/h).
lThe brake pedal is not pressed.
lThe clutch pedal is not pressed (manual gearbox only).
lThe gearbox is not in park, reverse or neutral (automatic gearbox only).
Function
The cruise control ECU receives the set signal and determines the vehicle speed provided by the SLABS ECU. The
cruise control ECU activates the vacuum pump assembly to move the pneumatic actuator and the linkage to the
throttle disc to maintain set road speed. It does this by controlling the vacuum to the pneumatic actuator.
Cruise control cancellation
Cancelling cruise control enables the driver to regain control of the vehicle speed by using the accelerator pedal.
Cruise control is cancelled if any of the following conditions occur:
lThe brake pedal is pressed.
lThe RES switch button is pressed.
lThe clutch pedal is pressed (manual gearbox only).
lThe cruise control master switch is turned off.
lThe gearbox is placed in park, neutral, or reverse (automatic gearbox only).
Function
The cruise control ECU cancels cruise control operation by opening a vacuum control valve in the vacuum pump
assembly. This releases the throttle linkage from the control of the pneumatic actuator and returns it to the control of
the accelerator pedal.
The set speed will be stored in the cruise control ECU unless:
lThe cruise control master switch is turned off.
lThe ignition switch is turned off.
If cruise control is deactivated using either of the above methods, the set speed will be erased from the memory of
the cruise control ECU.
Cruise control resume
Cruise control can be resumed at the previously set speed, provided the set speed has not been erased from the
cruise control ECU memory as described above. To resume cruise control operation to the previously set speed,
depress the RES switch once when the following conditions are met:
lA set speed is stored in the cruise control ECU.
lVehicle speed is between 28 - 125 mph (45 - 200 km/h).
lThe brake pedal is not pressed.
lThe clutch pedal is not pressed (manual gearbox only).
lThe gearbox is not in park, reverse or neutral (automatic gearbox only).
Function
The cruise control ECU activates the vacuum pump assembly to move the pneumatic actuator. This moves the
throttle to the set speed by adjusting the position of the throttle disc.

ENGINE MANAGEMENT SYSTEM - V8
18-2-80 REPAIRS
Coil - ignition
$% 18.20.45
Remove
1.Remove upper inlet manifold assembly.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - upper - Without Secondary Air
Injection.
2.Disconnect multiplugs from ignition coils.
3.Release ht leads from rocker covers and
disconnect ht leads from spark plugs.
4.Carefully manoeuvre ignition coil assembly
from between engine and bulkhead. 5.Noting their fitted position disconnect ht leads
from ignition coil.
6.Remove 3 screws securing ignition coil to
support bracket and remove coils.
Refit
1.Position ignition coil to support bracket, fit and
tighten screws.
2.Connect ht leads to ignition coil ensuring they
are in the correct position.
3.Carefully position ignition coil assembly
between engine and bulkhead.
4.Connect ht leads to spark plugs and secure ht
leads to rocker covers.
5.Connect multiplugs to ignition coils.
6.Fit upper inlet manifold assembly.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - upper - Without Secondary Air
Injection.

ENGINE MANAGEMENT SYSTEM - V8
18-2-92 REPAIRS
Valve - idle air control (IACV)
$% 19.22.54
Remove
1.Disconnect multiplug from IACV.
2.Loosen 2 clips securing air hoses and release
hoses.
3.Remove 2 screws securing IACV to inlet
manifold.
4.Collect clamps and remove IACV.
Refit
1.Position IACV to inlet manifold, locate clamps,
fit screws and tighten to 8 Nm (6 lbf.ft).
2.Position air hoses to IACV and secure clips.
3.Connect multiplug to IACV.
Injectors
$% 19.60.12
Remove
1.Remove upper manifold.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - upper - Without Secondary Air
Injection.
2.Carefully manoeuvre ignition coil assembly
from between inlet manifold and bulkhead.
3.Position absorbent cloth beneath fuel pipe to
catch spillage.
4.Disconnect fuel feed hose from fuel rail
CAUTION: Always fit plugs to open
connections to prevent contamination.
5.Release injector harness from fuel rail and
disconnect injector multiplugs.

ENGINE MANAGEMENT SYSTEM - V8
REPAIRS 18-2-93
6.Remove 4 bolts securing fuel rail to inlet
manifold.
7.Release injectors from inlet manifold and
remove fuel rail and injectors.
8.Release spring clips securing injectors to fuel
rail and remove fuel injectors.
9.Remove and discard 2 'O' rings from each
injector.
10.Fit protective caps to each end of injectors. Refit
1.Clean injectors and recesses in fuel rail and
inlet manifold.
2.Lubricate new 'O' rings with silicone grease
and fit to each end of injectors.
3.Fit injectors to fuel rail and secure with spring
clips.
4.Position fuel rail assembly and push-fit each
injector into inlet manifold.
5.Fit bolts securing fuel rail to inlet manifold and
tighten to 9 Nm (7 lbf.ft).
6.Connect fuel feed hose to fuel rail.
7.Connect injector harness multiplugs and
secure to fuel rail.
8.Carefully position ignition coil assembly
between inlet manifold and bulkhead.
9.Fit upper manifold.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - upper - Without Secondary Air
Injection.

FUEL DELIVERY SYSTEM - V8
19-2-6 DESCRIPTION AND OPERATION
Fuel pump, regulator and fuel gauge sender
1Electrical connector
2Fuel feed pipe coupling
3Pump feed pipe
4Fuel regulator return pipe
5Fuel gauge sender unit
6Float
7Gauze filter
8Swirl pot
9Pump electrical connections10Pump
11Spring 2 off
12OBD pressure sensor (NAS vehicles with
vacuum type EVAP system leak detection
capability only)
13Fuel pressure regulator
14'O' ring
15'O' ring
The fuel pump is a 'self priming' wet type pump which is immersed in fuel in the tank. The fuel pump operates at all
times when the ignition switch is in position II. If the engine is not started, the ECU will 'time-out' after 2 seconds and
de-energise the fuel pump relay to protect the pump. The pump receives a feed from the battery via fuse 10 in the
engine compartment fusebox and the fuel pump relay. The relay is energised by the ECM when the ignition switch is
moved to position II.
The fuel pump is retained with a locking ring and sealed with a rubber seal. The locking ring requires a special tool
for removal and fitment. An access panel for the fuel pump is located in the loadspace floor below the loadspace
carpet. The access panel is sealed to the floor with a rubber seal and retained by six self-tapping screws.
The fuel gauge sender is integral with the fuel pump. The sender is submerged in the fuel and is operated by a float
which moves with the fuel level in the tank.

FUEL DELIVERY SYSTEM - V8
19-2-10 DESCRIPTION AND OPERATION
Operation
When the ignition switch is moved to position II, the fuel pump relay in the engine compartment fusebox is energised
by the ECM. Battery voltage is supplied from the fuel pump relay to the fuel pump which operates. If engine cranking
is not detected by the ECU within a thirty second period, the ECU will 'time-out', de-energising the fuel pump relay.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
The fuel pump draws fuel from the swirl pot and pumps it along the fuel feed pipe to the injector fuel rail on the engine.
When the pressure in the fuel feed line reaches 3.5 bar (50 lbf.in
2) the fuel pressure regulator opens and relieves
pressure by directing fuel back into the swirl pot. The pressure regulator is constantly opening and closing to maintain
the pressure in the fuel feed pipe and the fuel rail at 3.5 bar (50 lbf.in
2).
The pressure is felt at each of the eight injectors connected to the fuel rail. The ECM controls the injection timing and
energises each injector to allow a metered amount of fuel at pump pressure to be injected into the inlet tract of the
inlet manifold. The atomised fuel from the injector is mixed with air from the inlet manifold before passing into the
cylinder.

MANIFOLDS AND EXHAUST SYSTEMS - V8
DESCRIPTION AND OPERATION 30-2-5
Description
General
The inlet manifold on the V8 engine is located on the top of the engine, between the cylinders. The manifold directs
intake air into the cylinders. The intake air is mixed with fuel delivered by the injectors prior to ignition in the cylinders.
The inlet manifold comprises three separate aluminium castings.
Two exhaust manifolds are used, one for each bank of four cylinders. Each exhaust manifold allows combustion
gases from the cylinders to leave the engine and directs them into the exhaust system.
The exhaust system is connected to each exhaust manifold and merges into one pipe midway along the underside of
the vehicle. A catalytic converter (where fitted) is located in the front pipe from each manifold. A silencer is installed
midway along the system and a second tail silencer is located at the rear of the vehicle.
Inlet manifold
The inlet manifold comprises three aluminium castings; a lower manifold, an upper manifold and a plenum. The inlet
manifold is located on the top of the engine and feeds air into the cylinders.
Lower manifold
The lower manifold is a one piece machined aluminium casting which locates in the vee on the top of the engine and
is secured to each cylinder head with six bolts per head. A one piece coated metal gasket seals the lower manifold to
each cylinder head and also serves as a cover for the cylinder block.
Eight injectors are fitted into the lower manifold, four on each side. Each injector is sealed in the manifold with O-ring
seals and retained in position by the fuel rails. A fuel rail is attached to each side of the manifold and secured with two
bolts.
Eight air intake ports are cast and machined on the top of the manifold, each port directing intake air into one cylinder.
These ports mate with matching ports in the upper manifold and are sealed with a coated metal gasket between the
two manifolds.
A cavity at the front of the manifold collects coolant flow from the engine. A coolant outlet pipe is sealed and attached
to the front of the manifold and provides for coolant to flow through the cavity in the casting to the radiator top hose.
A smaller port in the manifold also allows coolant to flow from the cavity to the heater matrix. The lower manifold also
locates the Engine Coolant Temperature (ECT) sensor in a port in the front of the manifold.
Upper manifold
The upper manifold is a one piece machined aluminium casting. The manifold has eight ports on its lower face which
mate with the eight ports on the lower manifold. The joint between the upper and lower manifolds is sealed with a
coated metal gasket and secured with six bolts.
The manifold divides from the eight ports into eight branches, four on each side. Each set of four branches merge into
one gallery on each side of the manifold. Each gallery has an opening at its forward end which mates with the intake
plenum.
The upper manifold provides attachment for the Idle Air Control (IAC) valve and for brackets which retain pipes, plug
leads and throttle cables.
Inlet plenum
The plenum is mounted transversely on the front of the upper manifold. The plenum divides into two galleries which
connect with the galleries on the upper manifold. The plenum is secured to the upper manifold with four bolts and
sealed with a coated metal gasket.
The plenum provides attachment for the throttle housing, which is secured with four bolts and sealed with a coated
metal gasket. The plenum also has vacuum connections for brake servo, rocker cover breather and fuel vapour from
the charcoal canister. A port on the top of the plenum connects via a hose to the IAC valve.

MANIFOLDS AND EXHAUST SYSTEMS - V8
30-2-16 REPAIRS
12.Disconnect brake servo vacuum pipe from inlet
plenum.
13.Disconnect breather hose from inlet plenum.
14.Remove bolt securing coolant rails.
15.Release engine harness from bulkhead clips
and position aside.
16.Remove 4 bolts securing ignition coils and
position ignition coils aside. 17.Release plug leads from upper manifold clips.
18.Disconnect multiplug from IACV.
19.Release and disconnect IACV hose.