steering wheel LAND ROVER DISCOVERY 1995 User Guide

19FUEL SYSTEM
2
DESCRIPTION AND OPERATION CRUISE CONTROL SYSTEM - V8i/Tdi AUTO EDC
Description
The cruise control system consists of
electro-mechanical devices, and comprises of the
following components.
ELECTRONIC CONTROL UNIT (ECU)
The microprocessor based ECU evaluates the signals
provided by the driver controls, brake pedal switch,
clutch pedal switch on manual models, and the
vehicle speed sensor. The ECU activates the vacuum
pump as required. The ECU also has a memory
function for set speed storage.
Driver operated switches
The main cruise control switch is located in the
auxiliary switch panel and activates the cruise control
system. The steering wheel switches provide
'set/accelerate' and 'resume/decelerate' features.
These switches provide the interface between driver
and cruise control system.
Brake pedal switch
The brake pedal switch is located under the lower
dash attached to the brake pedal mounting bracket.
The switch provides for fast disengagement of the
cruise control system and rapid return of the throttle
levers to the idle position when the brake pedal is
applied.
Clutch pedal switch
The clutch pedal switch is located under the lower
dash attached to the clutch pedal mounting bracket.
The switch provides for fast disengagement of the
cruise control system and rapid return of the throttle
levers to the idle position when the clutch pedal is
applied.Vehicle speed sensor
The vehicle speed sensor is located on the side of the
transfer box adjacent to park brake. The sensor
provides road speed data to the ECU. The cruise
control system cannot be engaged until the road
speed exceeds 45 km/h, (28 mph) the system will
automatically disengage at a road speed of 42 km/h
(26 mph).
Vacuum pump
The vacuum pump is energised when the main cruise
control switch is operated, and is actuated by the
steering wheel and brake pedal switches. The pump
provides a vacuum source to the cruise control
actuator. A control valve in the pump provides for
steady increase of road speed or purge of the system
when the brake pedal is applied.
Actuator
The actuator provides the servo mechanism link
between the cruise control system and throttle linkage
and is operated by vacuum from the vacuum pump.
Neutral lockout relay - automatic vehicles
The relay module is located in the right hand side
footwell, accessible by removing the trim casing.
The function of the relay module is to disengage the
cruise control system if neutral, or park, is selected in
the main gearbox, when the system is engaged.
Engine speed trip ECU - Manual vehicles
This unit is located in the right hand side footwell,
accessible by removing the trim casing.
The function of the unit is to disengage cruise control
if engine speed exceeds 5000 rev/min.

19FUEL SYSTEM
2
REPAIR ENGAGEMENT (ON/OFF) SWITCH
Service repair no - 19.75.30
Switch Replacement
Remove
1.Disconnect battery negative lead.
2.Carefully release auxiliary switch panel from
fascia.
3.Disconnect multiplug from switch.
4.Depress retaining lugs on switch, remove switch
from panel.
Bulb replacement
5.Position switch to facilitate removal of bulb.
6.Rotate bulb holder 90°and withdraw it from
switch.CRUISE CONTROL SWITCH
Service repair no - 19.75.36
Remove
1.Disconnect battery negative lead.
2. Models fitted with airbags:Remove driver's
airbag module.
See SUPPLEMENTARY
RESTRAINT SYSTEM, Repair, Driver's
Airbag Module
3. Models without airbags:Turn steering wheel
through 90°. Remove 2 Torx screws securing
pad to steering wheel and remove steering
wheel pad.
4.Disconnect cruise control switch multiplug from
main harness.

CRUISE CONTROL
3
REPAIR
5.Disconnect 2 Lucars from horn contacts.
6.Remove 2 screws securing cruise control switch
to steering wheel.
7.Remove 3 bolts securing mounting bracket to
steering wheel and remove mounting bracket.
8.Remove cruise control switch from steering
wheel.
Refit
9.Reverse removal procedure. Ensuring wiring
harness is routed correctly.
10. Models fitted with airbags:Refit driver's airbag
module and follow all safety precautions.
See
SUPPLEMENTARY RESTRAINT SYSTEM,
Repair, Driver's Airbag Module
ROTARY COUPLER
Service repair no - 19.75.54
The rotary coupler is located behind the steering
wheel. Access is gained by removing the steering
wheel and steering column shroud.
NOTE: On vehicles fitted with airbags.See
SUPPLEMENTARY RESTRAINT SYSTEM,
Repair, Rotary Coupler
Remove
1.Disconnect battery negative lead.
2.Remove steering wheel.
See STEERING,
Repair, Steering Wheel
3.Release 2 turnbuckles securing lower dash
closing panel and lower.
4.Remove 3 screws securing lower half of shroud
to steering column.
5.Disconnect rotary coupler multiplug from
steering column harness.

19FUEL SYSTEM
4
REPAIR
NOTE: If rotary coupler is to be re-used a
piece of adhesive tape should be placed
around the moulding in position A to
prevent rotation. Failure to do this may result in
damage to the wires inside the coupler.
6.Release clips securing rotary coupler to column
stalk assembly.
7.Remove rotary coupler from column stalk
assembly.
CAUTION: Ensure front wheels are in the
straight ahead position before removal
and refitting. Store in a plastic bag. DO
NOT rotate mechanism whilst removed.
Refit
8.Reverse removal procedure. Ensuring that the
column harnesses are not trapped by the
column shroud.
NOTE: If original rotary coupler is to be
fitted and there is evidence of tampering, it
is imperative that the coupler is
centralised.
See SUPPLEMENTARY RESTRAINT
SYSTEM, Repair, Rotary Coupler
NOTE: If a new rotary coupler is to be
fitted and the sealing tape is broken it
MUST NOT be used. Ensure rotary coupler
lugs are correctly engaged in the rear of the
steering wheel.ACTUATOR - V8i
Service repair no - 19.75.12
NOTE: The actuator is non serviceable, fit
a new unit if failure or damage occurs.
Remove
1.Disconnect battery negative lead.
2.Disconnect vacuum hose from actuator.
3.Remove nut securing actuator to throttle bracket.
4.Remove actuator, and manoeuvre actuator
operating link off throttle lever.
5.Withdraw actuator.
Refit
6.Inspect rubber diaphragm. Fit a new actuator
assembly if diaphragm is damaged.
7.Reverse removal procedure. Fitting the hook
uppermost.

FRONT AXLE AND FINAL DRIVE
1
REPAIR FRONT AXLE ASSEMBLY
Service repair no - 54.15.01
Remove
WARNING: Remove and refit of axle
requires a further two persons to steady
axle when lowering or repositioning axle.
1.Support chassis front.
2.Remove road wheels.
3.Support axle weight with hydraulic jack.
4.Remove radius arms to chassis frame nuts.
5.Disconnect steering damper from track rod.
Using a extractor remove track rod links from
swivel pin arms.
6.Remove four nuts and bolts securing radius
arms to axle bracket.
7.Remove radius arms.
8.Remove bolts securing brake hose brackets.
Refit bolts to prevent oil leakage.
9.Remove ABS sensor, if applicable.
10.Remove bolts from brake calipers and tie to one
side.
11.Remove nuts and washers securing shock
absorbers to axle.
12.Disconnect drag link from swivel pin housing
arm.
13.Remove two nuts and bolts securing panhard
rod to axle bracket. Lift rod clear of axle.
14.Mark for reassembly drive shaft flanges.
Remove four nuts and bolts, tie propeller shaft to
one side.
15.Lower axle assembly and remove road springs.
16.Disconnect anti-roll[sway] bar link.
See FRONT
SUSPENSION, Repair, Anti-Roll[Sway] Bar
Ball Joint Links
17.Remove axle assembly.
Refit
18.Position axle under vehicle, supporting left side
of axle.
19.Reverse removal procedure.
20.Tighten propeller shaft bolts to
47 Nm.
21.Tighten panhard rod to axle bracket to88 Nm.
22.Tighten drag link to hub arm to40 Nm.
23.Tighten upper swivel pin bolts.See
Specifications, torque, Torque Values
24.Tighten radius arms to axle bolts to197 Nm.
25.Tighten radius arms to chassis side member
nuts to
197 Nm.
26.Tighten track rod end to40 Nm.
Fit new split [cotter] pin.

STEERING
1
DESCRIPTION AND OPERATION DESCRIPTION
The power assisted steering system incorporates a
compression joint in the lower shaft, designed to
collapse on impact and for certain countries, an air
bag located in the centre of the steering wheel.
The mis-alignment of the upper steering column with
the steering box and the inclusion of two universal
joints and a compression joint in the lower shaft, is
also designed to prevent frontal impact moving the
column toward the driver.
The steering box is located behind the first cross
member of the chassis and is connected to the road
wheels by the drag link and track rod. An hydraulic
damper absorbs shocks in the steering, caused by
road wheel deflections when operating on rough
terrain.Power steering system
The power steering system comprises a hydraulic
pump which is belt driven from the engine and
supplied with fluid from a reservoir that also acts as a
cooler.
The steering box houses a self neutralizing rotary
valve which is part of the worm/valve assy and a
hydraulic piston/rack to assist the mechanical
operation.
The rotary valve which is operated by movement of
the steering wheel, directs fluid pressure to the
appropriate side of the hydraulic piston/rack to provide
assistance.
Power steering system
1. Hydraulic pump
2. Fluid reservoir
3. Steering box
4. Upper column
5. Universal joints
6. Lower shaft
7. Compression joint
8. Drag link

STEERING
3
DESCRIPTION AND OPERATION Steering column components
1. Upper shroud
2. Column harness
3. Cruise control switch (if fitted)
4. Steering wheel and nut
5. Rotary coupler
6. Column switch
7. Shear bolts
8. Switch saddle
9. Upper steering column
10. Universal joint
11. Universal joint bolt
12. Steering column lock assembly13. Lower shroud
14. Column lock/ignition
15. Air bag mounting bracket (if fitted)
16. Air bag module
17. Steering pad (non-airbag)
18. Lower shaft
19. Rubber coupling
20. Compression joint
21. Universal joint
22. Universal joint bolt

STEERING
5
DESCRIPTION AND OPERATION Rotary valve operation
The rotary valve assembly seen in RR3620M
comprises the worm (1), the valve sleeve (2), the input
shaft (4) and the torsion bar (5).
The valve sleeve is retained inside the worm by the
trim screw (3), and incorporates valve ports in its inner
bore. The input shaft is attached to the steering wheel
via the steering shaft and steering column and
incorporates valve ports in its outer diameter to align
with those in the sleeve. The torsion bar which is
secured to the worm and input shaft with pins (6) at
each end (later models use one pin at input shaft
end), holds the valve ports in neutral alignment when
there is no demand for assistance.No demand for assistance (Valve at neutral)
When there is no demand for assistance as seen in
RR3620M, the torsion bar holds the input shaft and
sleeve valve ports in neutral relationship to one
another, allowing equal pump pressure A to both
sides of the piston/rack (9). Any excess fluid flow from
the pump returns to the reservoir via B.
Rotary valve at neutral

57STEERING
6
DESCRIPTION AND OPERATION Demand for assistance (Valve misaligned)
When the steering wheel and input shaft is turned,
steering resistance transmitted to the worm causes
the torsion bar to be twisted and the valve ports to be
misaligned for a right or left turn. The misalignment of
the valve ports directs all fluid pressure A to one side
of the piston only and allows displaced fluid B on the
other side.When demanding maximum assistance, any
excessive fluid output from the pump due to high
pump speed, will circulate through the regulator valve
located in the pump unit, causing the temperature of
the fluid and the pump to rise rapidly.
To avoid excessive fluid temperatures which could
damage the oil seals, the steering must not be held on
full lock for more that 30 seconds in one minute.
Only when the steering wheel and the demand for
assistance is released, will the torsion bar return the
valve to neutral, allowing the fluid to circulate through
the reservoir where it is cooled.
In the unlikely event of mechanical failure of the
torsion bar, a coarse splined connection (7) between
the input shaft and worm, ensures steering control is
maintained sufficient to allow the vehicle to be
recovered.
Rotary valve misaligned

STEERING
7
DESCRIPTION AND OPERATION Pump and regulator valve operation
The pump which is belt driven from the engine is an
eccentric roller type and also houses the pressure
regulator and flow control valve. The pressure is
controlled by a spring loaded ball valve 3 which is
housed inside the flow control valve piston 4.
No demand for assistance High flow through box -
Low pressure
With no demand for assistance as illustrated in
RR3568M the rotary valve in the steering box acts as
a pressure relief valve, allowing fluid A to flow freely
through the steering box and back to the reservoir and
pump inlet B.
No demand for assistance
1. Reservoir
2. Pump
3. Pressure control ball valve and spring
4. Flow control valve and spring
5. Press fit plug (ball bearing)
6. Restrictor
The ball plug item 5 is pressed into the valve 4
during manufacture and determines the opening
pressure of pressure relief valve 3.No flow, through box - High pressure
When the steering is turned, the rotary valve
effectively stops all fluid flow through the steering box,
thus causing an increase in pressure A. This increase
in pressure is felt in the flow control valve spring
chamber where, at a pre-determined pressure the
relief valve 3 will open and allow the pressure to
escape. The fall in pressure in the flow control spring
chamber, allows the flow control valve to move to the
right, which in turn allows pump output A to escape
directly into the pump inlet B, as seen in RR3569M.Assistance demanded
As soon as the steering wheel is released after
making a turn, the system reverts to the condition
seen in RR3568M and the road wheels are returned
to the straight ahead position by the mechanical
steering geometry.
In the event of any hydraulic failure steering control
though heavy, will be maintained through the
mechanical components in the steering box.