ECU JAGUAR XJ6 1997 2.G Owner's Guide

3261 Jaguar XJ6
4
Chapter 4
Fuel and exhaust systems
Fuel system
Fuel pressure:kPa psi
Ignition ON, engine not running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 to 300 38 to 44
Engine idling:
Vacuum hose detached from fuel pressure regulator . . . . . . . . . . . 280 to 320 40 to 46
Vacuum hose attached to fuel pressure regulator . . . . . . . . . . . . . 210 to 260 30 to 38
Fuel system hold pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 21
Fuel injector resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 to 3.0 ohms
Idle speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Must be set by authorised service department
Torque wrench settingsNm lbf ft
Throttle body mounting bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 14
Fuel rail mounting bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9 Accelerator cable - removal, refitting and adjustment . . . . . . . . . . . 10
Air cleaner assembly - removal and refitting . . . . . . . . . . . . . . . . . . . 9
Catalytic converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 6
CHECK ENGINE light . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 6
Electronic Fuel Injection (EFI) system - check . . . . . . . . . . . . . . . . . . 12
Electronic Fuel Injection (EFI) system - component check
and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Electronic Fuel Injection (EFI) system - general information . . . . . . . 11
Exhaust manifold - removal and refitting . . . . . . . . . . . See Chapter 2A
Exhaust system check . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Exhaust system servicing - general information . . . . . . . . . . . . . . . . 14
Fuel filter renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1Fuel level sender unit - check and renewal . . . . . . . . . . . . . . . . . . . . 5
Fuel lines and fittings - inspection and renewal . . . . . . . . . . . . . . . . 6
Fuel pressure relief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Fuel pump - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Fuel pump/fuel pressure - check . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Fuel system check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Fuel tank - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Fuel tank cap gasket renewal . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Fuel tank cleaning and repair - general information . . . . . . . . . . . . . 8
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Intake manifold - removal and refitting . . . . . . . . . . . . See Chapter 2A
Underbonnet hose check and renewal . . . . . . . . . . . . . . See Chapter 1
4•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321
1 General information
The fuel system consists of a fuel tank, an
electric fuel pump either located externally,
next to the fuel tank (1988 to 1990 models) or
in the fuel tank (1991 to 1994 models), an EFI
fuel pump relay and main relay, an inertia
switch, fuel injectors and fuel rail, an air
cleaner assembly and a throttle body unit.
Multi Point Fuel Injection (MPFI)
system
Multi point fuel injection uses timed
impulses to sequentially inject the fuel directly
into the intake port of each cylinder. Theinjectors are controlled by the Electronic
Control Unit (ECU). The ECU monitors various
engine parameters and delivers the exact
amount of fuel, in the correct sequence, into
the intake ports. The throttle body serves only
to control the amount of air passing into the
system. Because each cylinder is equipped
with an injector mounted immediately
adjacent to the intake valve, much better
control of the fuel/air mixture ratio is possible.
Fuel pump and lines
Fuel is circulated from the fuel tank to the
fuel injection system, and back to the fuel
tank, through a pair of metal lines running
along the underside of the vehicle. On early
models (1988 to 1990), an electric fuel pump
is attached to the chassis next to the fueltank. On later models (1991 to 1994), the fuel
pump and fuel level sender unit are located
inside the fuel tank. A vapour return system
routes all vapours and hot fuel back to the fuel
tank through a separate return line.
The fuel pump will operate as long as the
engine is cranking or running and the ECU is
receiving ignition reference pulses from the
electronic ignition system (see Chapter 5). If
there are no reference pulses, the fuel pump
will shut off after 2 or 3 seconds.Inertia switch
These models are equipped with an inertia
switch that is wired in the circuit between the
fuel pump relay, the ignition switch and the
fuel pump (refer to the wiring diagrams at the
end of Chapter 12). The inertia switch is a

circuit. If all circuits are intact and not
damaged, check the inertia switch. Note: The
inertia switch is a special device that shuts
down power to the ignition and the fuel pump
in the event of an accident. See Chapter 12 for
checking and resetting procedures for the
inertia switch.
3Remove the relay and check for battery
voltage to the fuel pump relay connector (see
illustration). If there is battery voltage
present, check the relay for proper operation.
Refer to the relay checking procedure in
Chapter 12. Note:If battery voltage is not
available, check for battery voltage to the main
relay(see illustration). Refer to the relay
location diagrams in Chapter 12. The main
relay, which is located next to the fuel pump
relay, supplies voltage to the fuel pump and
ignition system.
4If battery voltage is present, check for
battery voltage directly at the fuel pump
electrical connector (see illustrations), within
two seconds of the ignition key being turned
On. If there is no voltage, check the fuel pump
circuit. If there is voltage present, renew the
pump (see Section 4). Note:It will be
necessary to raise the vehicle and support it
securely on axle stands to gain access to the
fuel pump electrical connectors. Have an
assistant operate the ignition key and be sure
to block the front wheels to avoid any
movement of the vehicle.
Operating pressure check
5Relieve the fuel system pressure (see
Section 2). Detach the cable from the negative
battery terminal.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
6Detach the fuel line from the fuel rail and
connect a fuel pressure gauge(see
illustrations)between the fuel pulsationdamper and the fuel rail. Tighten the hose
clamps securely.
7Attach the cable to the negative battery
terminal. Start the engine.
8Note the fuel pressure and compare it with
the pressure listed in this Chapter’s
Specifications.
9Disconnect the vacuum hose from the fuelpressure regulator and hook up a hand-held
vacuum pump (see illustration)to the port on
the fuel pressure regulator.
10Read the fuel pressure gauge with vacuum
applied to the pressure regulator and also with
no vacuum applied. The fuel pressure should
decrease as vacuum increases (and increase
as vacuum decreases).
Fuel and exhaust systems 4•3
4
3261 Jaguar XJ6 3.3a Checking for battery voltage at the fuel pump relay
connector ( 1989 model)
3.3b Checking for battery voltage to the main relay (1989 model)
3.6a Remove the fuel line from the fuel
pulsation damper . . .
3.4b Check for battery voltage to the
fuel pump on the harness connector near
the fuel tank on models with in-tank
fuel pumps3.4a Remove the rubber boot from the fuel
pump electrical connector and check for
voltage while an assistant turns the
ignition key (1989 model shown)
3.6b . . . then refit the fuel pressure gauge
between the fuel rail and the fuel pressure
damper using a T-fitting

11Reconnect the vacuum hose to the
regulator and check the fuel pressure at idle,
comparing your reading with the value listed
in this Chapter’s Specifications. Disconnect
the vacuum hose and watch the gauge - the
pressure should jump up considerably as
soon as the hose is disconnected. If it
doesn’t, check for a vacuum signal to the fuel
pressure regulator (see Step 14).
12If the fuel pressure is low, pinch the fuel
return line shut (see illustration)and watch
the gauge. If the pressure doesn’t rise, the
fuel pump is defective or there is a restriction
or leak in the fuel feed line, or the pump is
faulty. If the pressure rises sharply, renew the
pressure regulator.
13If the fuel pressure is too high, turn the
engine off. Disconnect the fuel return line and
blow through it to check for a blockage. If
there is no blockage, renew the fuel pressure
regulator.
14Connect a vacuum gauge to the pressure
regulator vacuum hose. Start the engine and
check for vacuum (see illustration). The fuel
pressure regulator receives manifold vacuum
that decreases (increases fuel pressure) when
the engine speed is raised (acceleration). If
there isn’t vacuum present, check for a
clogged hose or vacuum port. If the amount ofvacuum is adequate but the pressure is too
high, renew the fuel pressure regulator.
15Turn the ignition switch to OFF, wait five
minutes and recheck the pressure on the
gauge. Compare the reading with the
specified hold pressure. If the hold pressure is
less than specified:
a) The fuel lines may be leaking.
b) The fuel pressure regulator may be
allowing the fuel pressure to bleed
through to the return line.
c) A fuel injector (or injectors) may be
leaking.
d) The fuel pump may be defective.
4 Fuel pump-
removal and refitting
3
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
Note 1:On early models (1988 to 1990), an
electric fuel pump is attached to the chassis
next to the fuel tank. On later models (1991 to
1994), the fuel pump is inside the fuel tank.
Note 2: On 1988 to 1990 models, the fuel
pump may chatter excessively and the engine
may stall frequently during hot weather. If
stalling occurs, the engine will restart after a
cool-down period. Dual fuel pumps can be
installed by a dealer service department or
other qualified repair facility to remedy this
problem.
1Remove the fuel tank filler cap to relieve
any pressure in the fuel tank. Relieve the fuel
pressure (see Section 2).
2Disconnect the cable from the negative
terminal of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
External fuel pumps
3Raise the vehicle and support it securely on
axle stands.
4Disconnect the fuel lines from the fuel pump.
5Disconnect the electrical connectors from
the fuel pump (see illustration 3.4a).
6Remove the fuel pump bracket retaining
nuts (see illustration).
7Carefully withdraw the fuel pump from the
rubber case inside the fuel pump bracket and
angle the fuel pump over the rear suspension
and out near the wheel on the left side of the
vehicle.
8Refitting is the reverse of removal.
In-tank fuel pumps
9Raise the vehicle and support it securely on
axle stands.
10Disconnect the fuel pump and fuel level
sender unit electrical connectors and the fuel
lines.
11Remove the fuel tank from the boot (see
Section 7).
12Disconnect the fuel lines from the evap-
orative flange (see illustration). Remove the
lock ring with a hammer and brass punch,
tapping the lock ring anti-clockwise.
13Withdraw the fuel pump module from the
fuel tank. Note: The fuel pump module is
4•4 Fuel and exhaust systems
3.14 Connect a vacuum gauge to the
vacuum line leading to the fuel pressure
regulator and check the vacuum source4.6 Remove the fuel pump mounting nuts
(arrowed) and slide the fuel pump out of
the rubber casing (1989 model shown)
3261 Jaguar XJ6 3.9 Check fuel pressure without vacuum applied to the fuel
pressure regulator, then with vacuum applied; fuel pressure
should DECREASE as vacuum INCREASES
3.12 Using a pair of pliers, squeeze the return line and observe
the fuel pressure increase (wrap a rag around the fuel line so you
don’t damage it)

tank. If there is any doubt about the
amount of fuel in the tank, drain the fuel
tank completely before attempting this
procedure (Section 7, paragraph 1).
9Disconnect the cable from the negative
terminal of the battery. Disconnect the fuel level
sender unit/fuel pump electrical connector.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
10Using a brass punch, tap on the lock ring
anti-clockwise (see illustration)until the tabs
align with the indentations in the fuel tank.
11Carefully angle the sender unit out of the
opening without damaging the fuel level float
(see illustration).
12Refitting is the reverse of removal.
6 Fuel lines and fittings-
inspection and renewal
2
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
Note:If there is a distinct knocking noise
coming from the dash when the engine is
idling, the fuel feed hose may have hardened,
restricting fuel flow and causing abnormal
sounds. Replace the fuel inlet (feed) hose with
a new one.
Inspection
1Once in a while, you will have to raise the
vehicle to service or renew some component
(an exhaust pipe hanger, for example).
Whenever you work under the vehicle, always
inspect fuel lines and all fittings and
connections for damage or deterioration.
2Check all hoses and pipes for cracks, kinks,
deformation or obstructions.
3Make sure all hoses and pipe clips attach
their associated hoses or pipes securely to
the underside of the vehicle.4Verify all hose clamps attaching rubber
hoses to metal fuel lines or pipes are a tight fit
between the hoses and pipes.
Renewal
5If you must renew any damaged sections,
use hoses or pipes constructed from exactly
the same material as the section you are
replacing. Do not refit substitutes constructed
from inferior or inappropriate material or you
could cause a fuel leak or a fire.
6Always, before detaching or disassembling
any part of the fuel line system, note the
routing of all hoses and pipes and the
orientation of all clamps and clips to assure
that new sections are identically installed.
7Before detaching any part of the fuel
system, be sure to relieve the pressure in the
tank by removing the fuel tank cap, then
relieve the fuel system pressure (Section 2).
Cover the fitting being disconnected with a
rag to absorb any fuel that may leak out.
7 Fuel tank-
removal and refitting
3
Warning: Petrol is extremely
flammable, so take extra
precautions when you work onany part of the fuel system. See the
Warning in Section 2.
1This procedure is much easier to perform if
the fuel tank is empty. Some models may have
a drain plug for this purpose. If for some reason
the drain plug can’t be removed, postpone the
job until the tank is empty or siphon the fuel
into an approved container using a siphoning
kit (available at most motor factors).
Warning: Do not start the
siphoning action by mouth!
2Remove the fuel filler cap to relieve fuel
tank pressure.
3Detach the battery negative cable.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
4If the tank is full or nearly full, drain the fuel
into an approved container.
5Raise the vehicle and place it securely on
axle stands.
6Remove the filler neck vent tube clamp (see
illustration)and separate the tube from the
fuel filler neck.
7Remove the fuel filler assembly bolts (see
illustration)and slide the large rubber boot
down the neck of the fuel tank. Note:These
vehicles are susceptible to clogging of the fuel
overflow line. If this happens, excess fuel or
4•6 Fuel and exhaust systems
7.6 Remove the clamp that retains the fuel
filler assembly to the filler neck7.7a Remove bolts (arrowed) that retain the
fuel filler assembly to the body and slide the
assembly down the filler neck of fuel tank
3261 Jaguar XJ6 5.10 Use a brass punch and remove the lock ring by tapping on it
in an anti-clockwise direction
5.11 Lift the fuel level sender unit assembly from the fuel tank at
an angle so as not to damage the float or arm

13Allow the bellcrank to return to the idle
position and test the adjustment once again
until the correct adjustment has been attained.
11 Electronic Fuel Injection
(EFI) system-
general information
1These models are equipped with an
Electronic Fuel Injection (EFI) system. This fuel
injection system is designed by Bosch butlicensed by Lucas and is called the Lucas LH
Engine Management system. The EFI system
is composed of three basic sub systems: fuel
system, air induction system and electronic
control system (see illustration).
Fuel system
2An electric fuel pump is located on the
chassis of the rear suspension (external) (1988
to 1990) or inside the fuel tank (1991 to 1994)
The fuel pump supplies fuel under constant
pressure to the fuel rail, which distributes fuel
evenly to all injectors. From the fuel rail, fuel is
injected into the intake ports, just above the
intake valves, by fuel injectors. The amount of
fuel supplied by the injectors is precisely
controlled by an Electronic Control Unit (ECU).
A pressure regulator controls system pressure
in relation to intake manifold vacuum. A fuel
filter between the fuel pump and the fuel rail
filters fuel to protect the components of the
system.
Air induction system
3The air system consists of an air filter
housing, a Mass Air Flow (MAF) sensor
(airflow meter), Intake Air Temperature (IAT)
sensor and a throttle body. The MAF sensor is
an information gathering device for the ECU.A heated element determines the temperature
differential by measuring the current changes
which in turn measures the mass (weight and
volume) of air entering the engine. This
information helps the ECU determine the
amount of fuel to be injected by the injectors.
The throttle plate inside the throttle body is
controlled by the driver. As the throttle plate
opens, the amount of air that can pass
through the system increases, so the
potentiometer opens further and the ECU
signals the injectors to increase the amount of
fuel delivered to the intake ports. Refer to
Chapter 6 for additional information on the
fuel injection system sensors, test procedures
and renewal procedures.
Electronic control system
4The Computer Control System controls the
EFI and other systems by means of an
Electronic Control Unit (ECU), which employs
a microcomputer. The ECU receives signals
from a number of information sensors which
monitor such variables as intake air volume,
intake air temperature, coolant temperature,
engine rpm, acceleration/deceleration and
exhaust oxygen content. These signals help
the ECU determine the injection duration
necessary for the optimum air/fuel ratio. Some
Fuel and exhaust systems 4•9
4
10.11 Rotate the bellcrank until it reaches
wide open throttle and make sure the
pointer aligns with the A on the bellcrank.
Adjust if necessary
11.1 Fuel injection and emission control component locations for the 3.6 litre 1989 XJ6
3261 Jaguar XJ6 1 Fuel pressure regulator (under
fuel rail)
2 Idle Speed Control (ISC) motor
3 Fuel pressure damper4 Bellcrank
5 Throttle body (below bellcrank)
6 Intake Air Temp. (IAT) sensor
7 Supplementary air valve8 Mass Airflow (MAF) sensor
9 Throttle potentiometer (under
throttle body)
10 Fuel rail11 Fuel injector
13 Ignition amplifier (below block
valve)
14 Distributor

of these sensors and their corresponding
ECU-controlled relays are not contained
within EFI components, but are located
throughout the engine compartment. For
further information regarding the ECU and its
relationship to the engine electrical and
ignition system, see Chapter 6.
12 Electronic Fuel Injection
(EFI) system- check
2
1Check the earth wire connections for
tightness. Check all wiring and electrical
connectors that are related to the system.
Loose electrical connectors and poor grounds
can cause many problems that resemble
more serious malfunctions.
2Check to see that the battery is fully
charged, as the control unit and sensors
depend on an accurate supply voltage in
order to properly meter the fuel.
3Check the air filter element - a dirty or
partially blocked filter will severely impede
performance and economy (see Chapter 1).
4If a blown fuse is found, renew it and see if
it blows again. If it does, search for a shorted
wire in the harness related to the system.
5Check the air intake duct from the MAF
sensor to the intake manifold for leaks, which
will result in an excessively lean mixture. Also
check the condition of the vacuum hoses
connected to the intake manifold.
6Remove the air intake duct from the throttle
body and check for carbon and residue build-
up. If it’s dirty, clean with aerosol carburettor
cleaner (make sure the can says it’s safe for
use with oxygen sensors and catalytic
converters) and a toothbrush.
7With the engine running, place a
stethoscope against each injector, one at a
time, and listen for a clicking sound, indicating
operation (see illustration).8If there is a problem with an injector,
purchase a special injector test light (noid
light) and refit it into the injector electrical
connector (see illustration). Start the engine
and make sure that each injector connector
flashes the noid light. This will test for the
proper voltage signal to the injector.Caution:
If the engine will not start and the noid
light indicates that each injector is
receiving the proper signal, there is a good
possibility that the injector(s) is stuck open
and allowing fuel into the combustion
chamber in excessive amounts. If the spark
plugs are fouled, detach the primary (low
voltage) wires from the ignition coil, disable
the fuel pump by removing the fuel pump
relay (see Section 2), remove the spark plugs
and crank the engine over. If fuel sprays from
the spark plug holes, the engine is flooded
and the fuel must be removed from the
combustion chambers.
9With the engine OFF and the fuel injector
electrical connectors disconnected, measure
the resistance of each injector (see
illustration). Each injector should measure
about 2.0 to 3.0 ohms. If not, the injector is
probably faulty.10The remainder of the system checks
should be left to a Jaguar service department
or other qualified repair workshop, as there is
a chance that the control unit may be
damaged if not performed properly.
13 Electronic Fuel Injection
(EFI) system- component
check and renewal
3
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
Throttle body
Check
1Verify that the throttle linkage operates
smoothly.
2Start the engine, detach each vacuum hose
and, using your finger, check the vacuum at
each port on the throttle body with the engine
at idle and above idle. The vacuum available
from the throttle body is ported. Raise the
engine rpm and watch as vacuum increases.
It may be necessary to use a vacuum gauge.
Refer to Chapter 2B for additional information
concerning vacuum checks.
Renewal
Warning: Wait until the engine is
completely cool before
beginning this procedure.
3Detach the cable from the negative terminal
of the battery (see the Cautionat the
beginning of this Section).
4Drain the radiator (see Chapter 1).
4•10 Fuel and exhaust systems
12.9 Using an ohmmeter, measure the
resistance across both terminals
of the injector
3261 Jaguar XJ6 12.7 Use a stethoscope or a screwdriver to determine if the
injectors are working properly - they should make a steady
clicking sound that rises and falls with engine speed changes
12.8 Refit the “noid” light into the fuel injector electrical
connector and check to see that it blinks with the engine running

36Remove the fuel rail with the fuel injectors
attached (see illustration).
37Prise off the clips and remove the fuel
injector(s) from the fuel rail (see illustration).
38If you are replacing the injector(s), discard
the old injector. If you intend to re-use the
same injectors, renew the grommets and
O-rings (see illustrations).
39Refitting of the fuel injectors is the reverse
of removal. Apply a light film of clean engine
oil to the O-rings before refitting them.
40Tighten the fuel rail mounting bolts to the
torque listed in this Chapter’s Specifications.
Fuel pressure regulator
Check
41Refer to the fuel pump/fuel pressure
check procedure (see Section 3).
Renewal
42Relieve the fuel pressure (see Section 2)
and detach the cable from the negative
terminal of the battery (see the Cautionat the
beginning of this Section).
43Detach the vacuum hose from the
regulator.
44Remove the fuel rail and the injectors as
an assembly (see Steps 30 to 39).
45Remove the fuel line from the fuel
pressure regulator (see illustration).
46Remove the fuel pressure regulator
mounting bolts and detach the pressure
regulator from the engine.
47The remainder of refitting is the reverse of
removal. Make sure the fuel lines are secure
and there are no leaks before using the car.
Supplementary air valve
Check
48The supplementary air valve provides
additional throttle valve bypass air during cold
starting and cold running conditions below
15° F. This output actuator is controlled by the
computer (ECU) in response to informationreceived from the coolant temperature sensor,
intake air temperature sensor and other
information sensors working with the fuel
injection system.
49Check for battery voltage to the
supplementary air valve. With the engine cold,
backprobe the electrical connector using a
long pin and check for battery voltage (see
illustration). Voltage should exist.
50Because of the special tools required to
test the supplementary air valve, have it
tested by a dealer service department or other
qualified repair facility.
Renewal
51Remove the intake hoses, the mounting
screws and detach the supplementary air
valve from the engine.
52Refitting is the reverse of removal.
53Be sure to use a new gasket when refitting
the idle-up valve.
Air intake plenum
Note:The air intake plenum is removed and
installed as a complete unit with the intake
manifold. In the event of damage or leaks,
remove the air intake plenum and intake
Fuel and exhaust systems 4•13
4
3261 Jaguar XJ6 13.36 . . . and remove the fuel rail with the fuel injectors attached
13.37 Remove the fuel injector retaining clips from the fuel rail
using a small screwdriver
13.45 Disconnect the fuel pressure
regulator from the fuel return line
13.38b Pick out the old injector seal but
make sure the injector body is not
damaged in the process13.38a If you plan to refit the original
injectors, remove and discard the O-rings
and grommets and fit new ones
13.49 Check for battery voltage to the
supplementary air valve

same dimensions, amperage rating, cold
cranking rating, etc. as the original.
6Refitting is the reverse of removal.
4 Battery cables-
check and renewal
1
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
1Periodically inspect the entire length of
each battery cable for damage, cracked or
burned insulation and corrosion. Poor battery
cable connections can cause starting
problems and decreased engine performance.
2Check the cable-to-terminal connections at
the ends of the cables for cracks, loose wire
strands and corrosion. The presence of white,
fluffy deposits under the insulation at the
cable terminal connection is a sign that the
cable is corroded and should be renewed.
Check the terminals for distortion, missing
mounting bolts and corrosion.
3When removing the cables, always
disconnect the negative cable first and hook it
up last or the battery may be shorted by the
tool used to loosen the cable clamps. Even if
only the positive cable is being renewed, be
sure to disconnect the negative cable from
the battery first (see Chapter 1 for further
information regarding battery cable removal).
4Disconnect the cables from the battery,
then trace each of them to their opposite ends
and detach them from the starter solenoid
and earth terminals. Note the routing of each
cable to ensure correct refitting.
5If you are replacing either or both of the old
cables, take them with you when buying new
items. It is vitally important that you replace
the cables with identical parts. Cables have
characteristics that make them easy to
identify: positive cables are usually red, larger
in cross-section and have a larger diameter
battery post clamp; earth cables are usually
black, smaller in cross-section and have a
slightly smaller diameter clamp for the
negative post.
6Clean the threads of the solenoid or earth
connection with a wire brush to remove rust
and corrosion. Apply a light coat of battery
terminal corrosion inhibitor, or petroleum jelly,
to the threads to prevent future corrosion.
7Attach the cable to the solenoid or earth
connection and tighten the mounting nut/bolt
securely.
8Before connecting a new cable to the
battery, make sure that it reaches the battery
post without having to be stretched.
9Connect the positive cable first, followed by
the negative cable.
5 Ignition system- general
information and precautions
1All models are equipped with a computerised
ignition system. The ignition system consists of
the ignition coil, the crankshaft position sensor,
the amplifier and the electronic control unit
(ECU). The ignition ECU controls the ignition
timing and advance characteristics for the
engine. The ignition timing is not adjustable,
therefore, changing the position of the distributor
will not change the timing in any way. Note:In
the event the distributor must be removed from
the engine, be sure to follow the precautions
described in Section 9 and mark the engine and
distributor with paint to ensure correct refitting. If
the distributor is not marked and Ihe crankshaft is
turned while the distributor is out of the engine,
have the distributor installed by a dealer service
department. The distributor must be installed
using a special alignment tool.
2The distributor is driven by the intermediate
shaft which also drives the power steering pump.
The crankshaft position sensor is located on the
front timing cover. It detects crank position by
pulsing an electronic signal to the ECU. This
signal is sent to the ECU to provide ignition
timing specifications.
3The computerised ignition system provides
complete control of the ignition timing by
determining the optimum timing in response to
engine speed, coolant temperature, throttle
position and vacuum pressure in the intake
manifold. These parameters are relayed to the
ECU by the crankshaft position sensor, throttle
potentiometer, coolant temperature sensor and
MAF sensor. Ignition timing is altered during
warm-up, idling and warm running conditions by
the ECU. This electronic ignition system also
consists of the ignition switch, battery, coil,
distributor, spark plug leads and spark plugs.
4Refer to a dealer parts department or car
accessory outlet for any questions concerning
the availability of the distributor parts and
assemblies. Testing the crankshaft position
sensor is covered in Chapter 6.
5When working on the ignition system, take
the following precautions:
a) Do not keep the ignition switch on for
more than 10 seconds if the engine will
not start.
b) Always connect a tachometer in
accordance with the manufacturer’s
instructions. Some tachometers may be
incompatible with this ignition system.
Consult a dealer service department
before buying a tachometer for use with
this vehicle.
c) Never allow the ignition coil terminals to
touch earth. Earthing the coil could result
in damage to the igniter and/or the
ignition coil.
d) Do not disconnect the battery when the
engine is running.
6 Ignition system- check
2
Warning: Because of the high
voltage generated by the
ignition system, extreme care
should be taken when working
on the ignition components. This not only
includes the amplifier, coil, distributor and
spark plug leads, but related components
such as connectors, tachometer and other
test equipment also.
1With the ignition switch turned to the “ON”
position, a “Battery” light or an “Oil Pressure”
light is a basic check for ignition and battery
supply to the ECU.
2Check all ignition wiring connections for
tightness, cuts, corrosion or any other signs of a
bad connection.
3Use a calibrated ignition tester to verify
adequate secondary voltage (25,000 volts) at
each spark plug (see illustration). A faulty or
poor connection at that plug could also result in a
misfire. Also, check for carbon deposits inside
the spark plug boot.
4Check for carbon tracking on the coil. If
carbon tracking is evident, renew the coil and be
sure the secondary wires related to that coil are
clean and tight. Excessive wire resistance or
faulty connections could damage the coil.
5Check for battery voltage to the ignition coil
(see illustration). If battery voltage is available,
check the ignition coil primary and secondary
resistance (see Section 8).
6Check the distributor cap for any obvious
signs of carbon tracking, corroded terminals or
cracks (see Chapter 1).
7Using an ohmmeter, check the resistance of
the spark plug leads. Each wire should measure
less than 25,000 ohms.
8Check for battery voltage to the ignition
amplifier (see Section 7). If battery voltage does
not exist, check the circuit from the ignition
switch (refer to the wiring diagrams at the end of
Chapter 12).
5•2 Engine electrical systems
6.3 To use a calibrated ignition tester
(available at most car accessory outlets),
remove a plug lead from a cylinder,
connect the spark plug boot to the tester
and clip the tester to a good earth - if there
is enough voltage to fire the plug, sparks
will be clearly visible between the
electrode tip and the tester body
3261 Jaguar XJ6

9Check for battery voltage to the Ignition ON
relay (see illustration). If battery voltage does
not exist, check the circuit from the ignition ON
relay to the battery (refer to the wiring diagrams
at the end of Chapter 12). Note:See Chapter 12
for the location of the Ignition ON relay.
10Check the operation of the crankshaft
position sensor (see Chapter 6).
11If all the checks are correct, check the
voltage signal from the computer. Using an LED
type test light, backprobe the coil power lead
(negative terminal) on the ignition coil (see
illustration). Remove the coil secondary wire
and earth the terminal to the engine. Now have
an assistant crank the engine over and observe
that the test light pulses on and off. If there is no
flashing from the test light, most likely the
computer is damaged. Have the ECU diagnosed
by a dealer service department.
12Additional checks should be performed by a
dealer service department or an automotive
repair workshop.
7 Amplifier- check and renewal
2
Warning: Because of the high
voltage generated by the
ignition system, extreme care
should be taken whenever an
operation is performed involving ignitioncomponents. This not only includes the
amplifier, coil, distributor and spark plug
leads, but related components such as
connectors, tachometer and other test
equipment also.
Note:Because of the complexity and the
special tools required to test the amplifier, the
following procedure only describes a test to
verify battery voltage is reaching the amplifier.
If the wiring harness and the relays are
working properly and battery voltage is
available to the amplifier, have the ignition
system and the ECU diagnosed by a dealer
service department.
Check
1Disconnect the amplifier electrical connector
(see illustration).
2Turn the ignition key ON (engine not
running), check for battery voltage (see
illustration) to the amplifier.
3If no battery voltage is present, check the
harness from the ignition switch to the
amplifier. Refer to the wiring diagrams at the
end of Chapter 12.
Renewal
4Disconnect the negative battery terminal.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.5Remove the amplifier mounting bolts (see
illustration).
6Refitting is the reverse of removal.
8 Ignition coil-
check and renewal
2
Check
1Detach the cable from the negative terminal
of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
Engine electrical systems 5•3
5
6.5 Check for battery voltage to the
coil (+) terminal6.9 Check for battery voltage
to the IGN ON relay6.11 Refit the LED test light to the coil
negative (-) terminal, crank the engine over
and observe the light flash in response to
the trigger signal from the computer
7.1 Remove the clip that retains the
harness connector to the amplifier7.2 Check for battery voltage to the
ignition amplifier
7.5 Remove the amplifier mountings
screws (arrowed) and lift the unit from the
engine compartment
3261 Jaguar XJ6

sure you have the correct activation code
before disconnecting the battery.
2Disconnect the electrical connectors and
the coil wire from the coil.
3Using an ohmmeter, check the coil
resistance:
a) Measure the resistance between the
positive and negative terminals (see
illustration). Compare your reading with
the specified coil primary resistance listed
in this Chapter’s Specifications.
b) Measure the resistance between the
positive terminal and the high tension (HT)
terminal(see illustration). Compare your
reading with the specified coil secondary
resistance listed in this Chapter’s
Specifications.
4If either of the above tests yield resistance
values outside the specified amount, renew
the coil.
Renewal
5Detach the battery negative cable.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery. 6Label and disconnect the electrical wires
from the coil terminals.
7Remove the coil mounting fasteners (see
illustration).
8Refitting is the reverse of removal.
9 Distributor-
removal and refitting
2
Note:The timing on this ignition system cannot
be adjusted by turning the distributor. Ignition
timing is maintained by the ECU at all times. In
the event the distributor must be removed from
the engine, be sure to follow the precautions
described in this section and mark the engine
and distributor with paint to ensure correct
refitting. If the distributor is not marked, and the
crankshaft is turned while the distributor is out of
the engine, have the distributor installed by a
dealer service department. The distributor must
be installed using a special alignment tool.
Removal
1Detach the battery negative cable. Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
2Disconnect the electrical connectors from
the distributor.
3Look for a raised “1” on the distributor cap.
This marks the location for the number one
cylinder spark plug lead terminal. If the cap
does not have a mark for the number one
terminal, locate the number one spark plug
and trace the wire back to the terminal on the
cap.
4Remove the distributor cap (see Chapter 1)
and rotate the engine until the rotor is pointing
toward the number one spark plug terminal.
5Make a mark on the edge of the distributor
base directly below the rotor tip and in line
with it. Also, mark the distributor base and the
engine block to ensure that the distributor is
installed correctly (see illustrations).
6Remove the distributor hold-down bolt,
then pull the distributor out to remove it.
Caution: DO NOT turn the crankshaft while
the distributor is out of the engine, or the
alignment marks will be useless.
5•4 Engine electrical systems
8.3a To check the primary resistance of
the coil, measure the resistance between
the positive and the negative terminals8.3b To check the secondary resistance of
the coil, measure the resistance between
the positive terminal and the HT terminal8.7 Remove the nuts from the coil
mounting bracket (arrowed)
3261 Jaguar XJ6
9.5a Paint or scribe a mark (arrowed) on the edge of the
distributor housing below the rotor tip to ensure that the rotor is
pointing in the same direction when the distributor is reinstalled9.5b Paint or scribe another mark across the cylinder head and
the distributor body (arrowed) to ensure that the distributor is
aligned correctly when it is reinstalled