1988 OPEL VECTRA fuel pressure

4B
General
Injection system type:
C16 NZ, C16 NZ2, X16 SZ and C18 NZ . . . . . . . . . . . . . . . . . . . . . . . Multec Central Fuel Injection
20 NE, C20 NE and 20 SEH, (up to 1990) . . . . . . . . . . . . . . . . . . . . . Motronic M4.1
20 NE, C20 NE and 20 SEH, (from 1990) . . . . . . . . . . . . . . . . . . . . . . Motronic M1.5
20 XEJ and C20 XE, (up to 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motronic M2.5
C20 XE (from 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motronic M2.8
X20 XEV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simtec 56.1
Fuel tank capacity:
All models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.0 ± 2 litres
Fuel octane rating *
Leaded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 RON (4-star)
Unleaded (refer to Chapter 5) * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 RON (Premium)
* Note
: Models fitted with a catalytic converter (engine code prefixed by ‘C’ or ‘X’), must only be operated on unleadedfuel.
Idle settings
Idle speed:
C16 NZ and X16 SZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 80 rpm
C16 NZ2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880 ± 80 rpm
C18 NZ
Manual transmission models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880 ± 80 rpm
Automatic transmission models . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 ± 80 rpm
20 NE, C20 NE and 20 SEH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 80 rpm
20 XEJ and C20 XE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 940 ± 80 rpm
X20 XEV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 160 rpm
Note:Idle speed adjustment is not possible on these models, for information only
Chapter 4 Part B:
Fuel and exhaust systems - fuel injection models
Air box - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Air cleaner - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Air filter element - renewal . . . . . . . . . . . . . . . . . . . . . . . .See Chapter 1
Airflow meter (if fitted) - removal and refitting . . . . . . . . . . . . . . . . . .25
Air mass meter (if fitted) - removal and refitting . . . . . . . . . . . . . . . . .26
Air temperature sensor (later models) - removal and refitting . . . . . . .7
Air temperature control - description and testing . . . . . . . . . . . . . . . .6
Depressurising the fuel system - general . . . . . . . . . . . . . . . . . . . . . . .8
Electronic Control Unit (ECU) - removal and refitting . . . . . . . . . . . . .35
Fuel filter (‘In-tank’ fuel pump models) - removal and refitting . . . . . .10
Fuel filter (‘Out-of-tank’ fuel pump models) - removal and refitting . . .9
Fuel flow damper - removal and refitting . . . . . . . . . . . . . . . . . . . . . .18
Fuel injection system - precautions . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Fuel injector (Multec system) - removal and refitting . . . . . . . . . . . . .29
Fuel injector (Multec system) - testing . . . . . . . . . . . . . . . . . . . . . . . .30
Fuel injectors (except Multec system) - removal and refitting . . . . . .28
Fuel pressure regulator - removal and refitting . . . . . . . . . . . . . . . . .21
Fuel pump - testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Fuel pump (‘In-tank’ fuel pump models) - removal and refitting . . . .13
Fuel pump (‘Out-of-tank’ fuel pump models) - removal and refitting .12
Fuel pump relay - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Fuel tank - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Fuel tank filler pipe - removal and refitting . . . . . . . . . . . . . . . . . . . . .15
Fuel tank sender unit - removal and refitting . . . . . . . . . . . . . . . . . . .17
General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Hot film mass airflow meter - removal and refitting . . . . . . . . . . . . . .27
Idle air control stepper motor - removal and refitting . . . . . . . . . . . . .33
Idle mixture - checking and adjustment . . . . . . . . . . . . . . . . . . . . . . .20
Idle speed adjuster - removal and refitting . . . . . . . . . . . . . . . . . . . . .22
Inlet manifold (DOHC models) - removal and refitting . . . . . . . . . . . .40
Inlet manifold (SOHC with Multec) - removal and refitting . . . . . . . . .39
Inlet manifold (SOHC without Multec) - removal and refitting . . . . . .38
Knock sensor and module (X16 SZ models) - removal and refitting .36
Knock sensor (Simtec system) - removal and refitting . . . . . . . . . . . .37
System testing - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Throttle body (except Multec system) - removal and refitting . . . . . .31
Throttle body (Multec system) - removal and refitting . . . . . . . . . . . .32
Throttle cable - removal, refitting and adjustment . . . . . . . . . . . . . . .19
Throttle pedal - removal and refitting . . . . . . . . . . . . . .See Chapter 4A
Throttle position sensor - removal and refitting . . . . . . . . . . . . . . . . .23
Throttle potentiometer - removal and refitting . . . . . . . . . . . . . . . . . .34
Throttle valve potentiometer - removal and refitting . . . . . . . . . . . . .24
4B•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

Idle settings (continued)
Idle mixture (CO content):
20 NE and 20 SEH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.0 max.
20 XEJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.7 to 1.2%
All other models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 % (at 2800 to 3200 rpm)
Fuel Pressure (regulator vacuum hose connected)
Multec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.76 bar
Motronic 4.1:
Feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3 to 2.7 bar
Return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 to 1.5 bar
Motronic 1.5:
Feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.8 to 2.2 bar
Return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 to 1.5 bar
Motronic 2.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.0 to 2.2 bar
Motronic 2.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2 to 2.7 bar
Simtec 56.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .not available
Torque wrench settingsNmlbf ft
All specifications as for carburettor models except for the following:
Bracket, tank vent valve to coolant flange . . . . . . . . . . . . . . . . . . . . . . .86
Fuel distributor pipe to inlet manifold . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Fuel flow damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2015
Fuel injector retainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Fuel pressure regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.52
Fuel pump clamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Idle air control stepper motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.52
Knock sensor (X16 SZ) to block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1310
Oxygen sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3022
Throttle body mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2015
Throttle body upper-to-lower section . . . . . . . . . . . . . . . . . . . . . . . . . . .64.5
Throttle potentiometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.5
Throttle valve housing to inlet manifold . . . . . . . . . . . . . . . . . . . . . . . . .97
1General description
General
1All engines available within the Cavalier
range can be operated on unleaded petrol.
Refer to Chapter 5 for further details. Note
that models fitted with a catalytic converter
must only be operated on unleaded petrol,
and leaded petrol must not be used. Models
with catalytic converter can be identified by
the engine code, which is prefixed by the
letter ‘C’ or ‘X’.
Multec system
Note: There is no provision for the adjustment
or alteration of the idle speed; if checking the
idle speed, remember that it may vary
constantly under ECU control.
2The Multec system is essentially a simple
method of air/fuel metering, replacing the
carburettor with a single injector mounted in a
throttle body. This type of system is therefore
also known as Throttle Body Injection (TBi),
Central Fuel Injection (CFi) or single-(or
mono-) point injection. The whole system is
best explained if considered as three
sub-systems, these being fuel delivery, air
metering and electrical control.
3The fuel delivery system incorporates the
fuel tank (with the electric fuel pumpimmersed inside it), the fuel filter, the fuel
injector and pressure regulator (mounted in
the throttle body), and the hoses and pipes
connecting them. When the ignition is
switched on (or when the engine is cranking,
on X16 SZ engines) the pump is supplied with
voltage, by way of the pump relay and fuse
11, under the control of the Electronic Control
Unit (ECU). The pump feeds through the fuel
filter to the injector. Fuel pressure is controlled
by the pressure regulator, which lifts to allow
excess fuel to return to the tank.
4The air metering system includes the inlet air
temperature control system and the air
cleaner, but its main components are in the
throttle body assembly. This incorporates the
injector, which sprays fuel onto the back of the
throttle valve, the throttle potentiometer. This
is linked to the throttle valve spindle and sends
the ECU information on the rate of throttle
opening by transmitting a varying voltage. The
idle air control stepper motor is controlled by
the ECU to maintain the idle speed.
5The electrical side of the fuel injection
system consists of the ECU and all the
sensors that provide it with information, plus
the actuators by which it controls the whole
system’s operation. The basic method of
operation is as follows; note that the ignition
system is controlled by the same ECU.
6The manifold absolute pressure sensor is
connected by a hose to the inlet manifold.
Variations in manifold pressure are converted
into graduated electrical signals that are usedby the ECU to determine the load on the
engine. The throttle valve potentiometer is
explained above.
7Information on engine speed and
crankshaft position comes from the distributor
on C16 NZ engines and from the crankshaft
speed/position sensor on C16 NZ2, X16 SZ
and C18 NZ engines.
8An odometer frequency sensor provides the
ECU with information on the vehicle’s road
speed, and the coolant temperature sensor
provides it with the engine temperature. A
knock sensor located in the cylinder block
between cylinders 2 and 3 on the X16 SZ
engine provides additional information to the
ECU by detecting pre-ignition (detonation)
during the combustion process.
9All these signals are compared by the ECU
with set values pre-programmed (mapped)
into its memory. Considering this information,
the ECU selects the response appropriate to
those values. It controls the ignition amplifier
module by varying the ignition timing as
required. The fuel injector is controlled by
varying its pulse width the time the injector is
held open, to provide a richer or weaker
mixture, as appropriate. The idle air control
stepper motor controls the idle speed. The
fuel pump relay controls the fuel delivery and
the oxygen sensor, accordingly. The mixture,
idle speed and ignition timing are constantly
varied by the ECU to provide the best settings
for cranking, starting and engine warm-up
(with either a hot or cold engine), idling,
4B•2Fuel and exhaust systems - fuel injection models

4B
cruising and accelerating. The injector earth is
also switched off on the overrun to improve
fuel economy and reduce exhaust emissions.
Additionally, on the X16 SZ engine, the ECU
also controls the operation of the charcoal
canister purge valve in the evaporative
emission control system.
10The oxygen sensor screwed into the
exhaust manifold provides the ECU with a
constant feedback signal. This enables it to
adjust the mixture (closed-loop control) to
provide the best possible conditions for the
catalytic converter to operate effectively.
11Until the oxygen sensor is fully warmed up
it gives no feedback so the ECU uses
pre-programmed values (open-loop control) to
determine the correct injector pulse width.
When the sensor reaches its normal operating
temperature, its tip (which is sensitive to
oxygen) sends the ECU a varying voltage
depending on the amount of oxygen in the
exhaust gases. If the inlet air/fuel mixture is too
rich, the exhaust gases are low in oxygen so the
sensor sends a low-voltage signal. The voltage
rises as the mixture weakens and the amount of
oxygen rises in the exhaust gases. Peak
conversion efficiency of all major pollutants
occurs if the inlet air/fuel mixture is maintained
at the chemically correct ratio for the complete
combustion of petrol of 14.7 parts (by weight) of
air to 1 part of fuel (the “stoichiometric” ratio).
The sensor output voltage alters in a large step
at this point, the ECU using the signal change
as a reference point and correcting the inlet
air/fuel mixture accordingly by altering the fuel
injector pulse width.
12In addition, the ECU senses battery
voltage, incorporates diagnostic capabilities,
and can both receive and transmit information
by way of the diagnostic connector, thus
permitting engine diagnosis and tuning by
Vauxhall’s TECH1, test equipment.
Motronic system
13The Motronic type is available in several
different versions, depending on model. The
system is under the overall control of the
Motronic engine management system (Chapter
5), which also controls the ignition timing.
14Fuel is supplied from the rear-mounted
fuel tank by an electric fuel pump mounted
under the rear of the vehicle, through a
pressure regulator, to the fuel rail. The fuel rail
acts as a reservoir for the four fuel injectors,
which inject fuel into the cylinder inlet tracts,
upstream of the inlet valves. On SOHC
engines, the fuel injectors receive an electrical
pulse once per crankshaft revolution, which
operates all four injectors simultaneously. On
DOHC engines, sequential fuel injection is
used, whereby each injector receives an
individual electrical pulse allowing the four
injectors to operate independently, which
enables finer control of the fuel supply to each
cylinder. The duration of the electrical pulse
determines the quantity of fuel-injected, and
pulse duration is computed by the Motronic
module, based on the information received
from the various sensors.15On SOHC engines, inlet air passes from
the air cleaner through a vane type airflow
meter, before passing to the cylinder inlet
tracts through the throttle valve. A flap in the
vane airflow meter is deflected in proportion
to the airflow; this deflection is converted into
an electrical signal, and passed to the
Motronic module. A potentiometer screw
located on the airflow meter provides the
means of idle mixture adjustment, by altering
the reference voltage supplied to the Motronic
module.
16On DOHC engines, inlet air passes from
the air cleaner through a hot wire type air
mass meter, before passing to the cylinder
inlet tracts through a two-stage throttle body
assembly. The electrical current required to
maintain the temperature of the hot wire in the
air mass meter is directly proportional to the
mass flow rate of the air trying to cool it. The
current is converted into a signal, which is
passed to the Motronic module. The throttle
body contains two throttle valves that open
progressively, allowing high torque at part
throttle, and full-throttle, high-speed
“breathing” capacity. A potentiometer screw
located on the air mass meter provides the
means of idle mixture adjustment, by altering
the reference voltage supplied to the Motronic
module.
17A throttle position sensor enables the
Motronic module to compute the throttle
position, and on certain models, its rate of
change. Extra fuel can thus be provided for
acceleration when the throttle is opened
suddenly. Information from the throttle
position sensor is also used to cut off the fuel
supply on the overrun, thus improving fuel
economy and reducing exhaust gas
emissions.
18Idle speed is controlled by a variable-
orifice solenoid valve, which regulates the
amount of air bypassing the throttle valve. The
valve is controlled by the Motronic module;
there is no provision for direct adjustment of
the idle speed.
19Additional sensors inform the Motronic
module of engine coolant temperature, air
temperature, and on models fitted with a
catalytic converter, exhaust gas oxygen
content.
20A fuel filter is incorporated in the fuel
supply line, to ensure that the fuel supplied to
the injectors is clean.
21A fuel pump cut-off relay is controlled by
the Motronic module, which cuts the power to
the fuel pump should the engine stop with the
ignition switched on, if there is an accident. All
1993-onwards models equipped with
Motronic systems, have their fuel pump
located inside the fuel tank.
22The later M2.8 system is basically the
same as the earlier M2.5 system apart from
the following:
a)Hot Film Mass Airflow Meter - The hot
wire type unit used previously is replaced
on the M2.8 system by a hot film mass
airflow meter. The operation is the sameexcept that a thin, electrically heated plate
rather than a wire is used. The plate is
maintained at a constant temperature by
electric current as the inlet air mass
passing over the plate tries to cool it. The
current required to maintain the
temperature of the plate is directly
proportional to the mass flow rate of the
inlet air. The current is converted to a
signal that is passed to the Motronic
module.
b)Inlet Air Temperature Sensor -The sensor
is located in the hose between the hot
film mass airflow meter and the air cleaner
for precise monitoring of inlet air
temperature. Signals from the sensor are
used in conjunction with other sensors to
indicate the occurrence of a hot start
condition. The Motronic module then
interprets these signals to alter injector
duration accordingly.
c)Throttle Valve Potentiometer -On the
M2.8 system a throttle valve
potentiometer replaces the throttle valve
switch used previously.
Simtec system
23An increased amount of electronic
components are used instead of mechanical
parts as sensors and actuators with the
Simtec engine management system. This
provides more precise operating data as well
as greater problem free motoring.
24The control unit is equipped with
electronic ignition control. Called ‘Micropro-
cessor Spark Timing System, inductive
triggered’, (or MSTS-i), and means that the
mechanical high voltage distributor is no
longer needed. It is located behind the trim
panel, on the right-hand side footwell (door
pillar).
25The ignition coil is replaced by a dual
spark ignition coil, which is switched directly
by the output stages in the control unit.
26A camshaft sensor will maintain
emergency operation, should the crankshaft
inductive pulse pick-up, malfunction. These
sense TDC (‘Top Dead Centre’), crankshaft
angle and engine speed. The signals are used
by the control unit to calculate ignition point
and for fuel injection.
27The ‘hot film airflow meter’ determines the
mass of air taken in by the engine. The system
uses this information to calculate the correct
amount of fuel needed for injection in the
engine.
28The air inlet temperature sensor (NTC), is
fitted in the air inlet duct between the air
cleaner and the hot mass air flow meter.
29A controlled canister purge valve is
actuated by the system. The tank ventilation is
monitored closely with the Lambda control (or
oxygen sensor) and adaptation by the
computer within the control unit.
30A knock control system is also fitted. This
eliminates the need for octane number
adjustment, as it is performed automatically
through the control unit.
Fuel and exhaust systems - fuel injection models 4B•3

31This engine is also fitted with an EGR
(exhaust gas recirculation) valve and
secondary air injection (AIR - Air Injection
Reactor), to conform to the latest European
exhaust emission limits (as from 1996). The
EGR returns a specific amount of exhaust gas
into the combustion process. This in turn
reduces the formation of nitrogen oxides
(No
x). The secondary air injection system has
an electrically driven air pump that injects air
into the exhaust manifold, reducing the
amount of CO and HC emissions.
2Fuel injection system -
precautions
The fuel injection system is pressurised,
therefore extra care must be taken when
disconnecting fuel lines. When disconnecting
a fuel line union, loosen the union slowly, to
avoid a sudden release of pressure that may
cause fuel to spray out.
Fuel pressure checking must be entrusted
to a Vauxhall dealer, or other specialist, who
has the necessary special equipment.
3System testing - general
3
General
1Apart from basic electrical tests, there is
nothing that can be done by the owner to test
individual fuel system components.2If a fault arises, check first that it is not due
to poor maintenance. Check that the air
cleaner filter element is clean, the spark plugs
are in good condition and correctly gapped.
Check also that the engine breather hoses are
clear and undamaged and that the throttle
cable is correctly adjusted. If the engine is
running very roughly, check the compression
pressures (Chapter 1) and remember the
possibility that one of the hydraulic tappets
might be faulty, producing an incorrect valve
clearance.
3If the fault is thought to be due to a dirty
injector, it is worth trying one of the
established injector-cleaning treatments
before renewing, perhaps unnecessarily, the
injector.
4If the fault persists, check the ignition
system components (as far as possible).
5If the fault is still not eliminated, work
methodically through the system, checking all
fuses, wiring connectors and wiring, looking
for any signs of poor connections, dampness,
corrosion, dirt or other faults.
6Once the system components have been
checked for signs of obvious faults, take the
vehicle to a Vauxhall dealer for the full system
to be tested on special equipment.
7Do not attempt to “test” any component,
but particularly the ECU, with anything other
than the correct test equipment, available at a
Vauxhall dealer. If any of the wires to be
checked lead to a component such as the
ECU, always first unplug the relevant
connector from the system components so
that there is no risk of the component being
damaged by the application of incorrect
voltages from test equipment.
4Air cleaner - removal and
refitting
2
Note:If ‘round type’ air filter is fitted, follow
procedure in Chapter 4A.
Removal
1Unclip the coolant expansion tank hose
from the air cleaner cover, and move it to one
side out of the way.2Loosen the clamp screw and disconnect
the air trunking from the airflow meter (see
illustration).
3Disconnect the battery negative lead, then
disconnect the wiring plug from the airflow
meter.
4Release the two securing clips from the left-
hand side of the air cleaner cover, and
unscrew the two captive securing screws
from the right-hand side, then lift off the
cover.
5Lift out the filter element.
6Loosen the preheat hoses, fastening nuts.
7Undo the nuts securing the 2 rubber block
studs which are secured through the lower
half of the air cleaner housing.
8Some models are fitted with an inlet air
resonance box, to reduce induction noise.
This box is located under the wheel arch, and
connects to a pipe on the air inlet tube.
9The resonance box must be removed
before the air inlet tube can be removed. To
do this, first apply the handbrake, then jack up
the front of the vehicle, and support securely
on axle stands placed under the body side
members.
10Remove the securing screws, and
withdraw the lower splash shield from the
wing to expose the resonance box.
11Unscrew the single securing screw, and
pull the resonance box from the connector
tube (see illustrations).
12If desired, the air inlet tube can be
removed after pulling off the connector tube
from under the wing (see illustration).
4B•4Fuel and exhaust systems - fuel injection models
4.12 Removing the resonance box
connector tube4.11B . . . and withdraw the resonance box4.11A Remove the securing screw . . .
4.2 Loosening the air trunking clamp
screw at the airflow meter
Warning: Many of the
procedures in this sub-Section
require the removal of fuel lines
and connections that may result
in some fuel spillage. Before carrying out
any operation on the fuel system refer to
the precautions given in Safety first! at
the beginning of this Manual and follow
them implicitly. Petrol is a highly
dangerous and volatile liquid, and the
precautions necessary when handling it
cannot be overstressed.

4B
13Manipulate the air inlet tube to release the
securing lugs from the front body panel. This
is a tricky operation, and patience will be
required. For improved access, the headlamp
can be removed, as described in Chapter 12.
Refitting
14Refitting of all components is a reversal of
removal, noting that the air cleaner element
fits with the rubber locating flange uppermost.
5Air box - removal and refitting
2
Removal
1The air box, if fitted, is secured by two or
three bolts to the top of the throttle body.
Take note of the routing and connections of
the inlet air temperature control system
vacuum pipes.
2Disconnect the engine breather hose from
the air box and the vacuum pipe from the
rearmost of the throttle body’s three unions
(see illustration).
3Do not lose the sealing ring as the air box is
withdrawn.
Refitting
4On refitting, ensure that the sealing ring is
seated correctly in the slot in the underside of
the air box, tighten the screws, and reconnect
the vacuum pipe and breather hose (see
illustrations).
6Air temperature control -
description and testing
3
Description
1Fitted to models with Multec systems, air
temperature is controlled by a thermac switch
(thermostat), mounted in the air box. When
the engine is started from cold, the switch is
closed to allow inlet manifold depression to
act on the air temperature control valve in the
air cleaner assembly. This uses a vacuum
servo in the valve assembly to draw a flap
valve across the cold air inlet thus allowing
only (warmed) air from the exhaust manifold to
enter the air cleaner.2As the temperature of the exhaust warmed
air in the air box rises, a bi-metallic strip in the
thermac switch deforms. This opens the
switch to shut off the depression in the air
temperature control valve. The flap is then
lowered gradually across the hot air inlet. Until
the engine is fully warmed up to normal
operating temperature, only cold air from the
front of the vehicle is entering the air cleaner.
Testing
3To check the system, allow the engine to
cool down completely, then remove the air
cleaner cover; the flap valve should be
securely seated across the hot air inlet. Start
the engine. The flap should immediately rise to
close off the cold air inlet. It should then lower
steadily as the engine warms until it is
eventually seated across the hot air inlet again.
4To check the thermac switch, disconnect
the control valve vacuum pipe from the switch
union (on the rear face of the air box) when the
engine is running. With the engine cold, full
inlet manifold depression should be felt
sucking at the union; none at all should be felt
when the engine is fully warmed up.
5To check the air temperature control valve,
remove the air cleaner cover; the flap valve
should be securely seated across the hot air
inlet. Disconnect the control valve vacuum
pipe from the switch union on the rear face of
the air box and suck hard on its end; the flap
should rise to shut off the cold air inlet.
6If either component is faulty, it must be
renewed. This means renewing the air cleaner
lower casing to obtain a new air temperature
control valve, or renewing the air box in the
case of the thermac switch.
7Air temperature sensor (later
models) - removal and
refitting
2
Removal
1Disconnect the battery negative lead.
2Disconnect the wiring plug at the inlet air
temperature sensor.
3Release the hose clips and remove the air
trunking then remove the inlet air temperature
sensor from the trunking.
Refitting
4Refitting is a reversal of removal but ensure
that the air trunking is connected to the
airflow meter as shown (see illustration).
8Depressurising the fuel
system - general
2
General
1The fuel system consisting of the
tank-mounted fuel pump, the fuel filter, the
fuel injector and the pressure regulator in the
throttle body. Metal pipes and flexible hoses
of the fuel lines connect these components.
All these contain fuel that will be under
pressure while the engine is running and/or
while the ignition is switched on.
2The pressure will remain for some time after
the ignition has been switched off and must
be relieved before any of these components
are disturbed.
3Remove either the fuel pump fuse (num-
ber 11) or the fuel pump relay and start the
engine. Allow the engine to idle until it cuts
out. Turn the engine over once or twice on the
starter to ensure that all pressure is released,
then switch off the ignition.
4Do not forget to refit the fuse or relay when
work is complete.
Fuel and exhaust systems - fuel injection models 4B•5
5.4B Do not overtighten the air box
screws
7.4 Removing the intake air temperature
sensor from the air trunking - later models
5.4A Ensure the sealing ring is located in
the air box groove5.2 Vacuum pipe connections to air box
A To throttle body B To air cleaner
Warning: The following
procedures will merely relieve
the pressure in the fuel system.
Remember that fuel will still be
present in the system components, so
take precautions before disconnecting
any of them. Refer to Section 2.

4B
9Run the engine and check for leaks on
completion. If leakage is evident, stop the
engine immediately, and rectify the problem
without delay.
13Fuel pump (‘In-tank’ fuel
pump models) - removal and
refitting
3
Removal
1Depressurise the fuel system (Section 8),
then remove and refit the fuel filler cap to
ensure that the pressure is equalised inside
and outside the tank.
2Disconnect the battery negative terminal.
3Fold forwards the rear seat cushion. Peel
back the floor covering beneath it, then
remove the cover plug from the vehicle floor
to reach the pump mountings (see
illustration).
4Noting exactly how it is connected, and
making your own marks or notes to ensure
that it can be reconnected the same way
round, disconnect the wiring plug from the
pump.
5Release the securing clip and disconnect
the fuel hose from the pump. Clamp or plug
the hose to prevent the loss of fuel and the
entry of dirt.
6Undo the pump mounting bracket screws,
then withdraw the mounting bracket and
pump assembly from the tank. Note the
position of the sealing ring and discard it, then
cover the tank opening as a safety measure
and to prevent the entry of dirt.
7If the pump is to be renewed, first move it to
a clean working area and carry out the
following.
8Prise off the filter at the base of the pump
assembly, then release the securing clamp
and disconnect the mounting
bracket-to-pump fuel hose.
9Making your own marks or notes to ensure
that they can be reconnected the same way
round, unsolder the wires connecting the
pump to the mounting bracket.
10Press the pump out of the rubber sleeve.
Refitting
11Reassembly and refitting are the reverse
of the removal and dismantling procedures,
noting the following points.a)Ensure that the pump is seated correctly
in the sleeve and that the hose is securely
fastened.
b)Ensure that the wires are correctly
reconnected and securely soldered.
c)Always renew the pump mounting
bracket’s sealing ring.
d)Apply a few drops of sealing compound
(i.e. Vauxhall part no. 90485251) to the
threads of the screws, then tighten them
securely, but take care not to distort the
sealing ring.
14Fuel pump relay - renewal
2
The relay is mounted in the engine
compartment relay box (Chapter 12). Where
more than one relay is fitted, the fuel pump
relay is the one with the black base.
15Fuel tank filler pipe - removal
and refitting
3
Removal
1Syphon out any remaining fuel in the tank
into a clean container that is designed for
carrying petrol and is clearly marked as such.
2Raise the bottom edge of the seal
surrounding the filler neck and undo the single
securing screw beneath.
3Chock the front wheels, jack up the rear of
the vehicle and support it securely on axle
stands (see “Jacking and Vehicle Support”)
placed under the body side members.
4Unscrew the single filler pipe mounting bolt
from the underbody, then work along the
length of the pipe, cutting or releasing any
clips or ties securing other pipes or hoses to
it. Releasing their clips, disconnect the filler
and vent hoses from the pipe’s lower end and
the small-bore vent hoses from the unions at
its upper end.
5Having ensured that all components have
been removed or disconnected which mightprevent its removal, manoeuvre the pipe away
from the vehicle’s underside.
6To check the operation of the pipe’s
anti-leak valve, invert the filler pipe and fill the
lower union (now uppermost) with petrol. If
the valve is functioning correctly, no petrol will
leak from the other union. If petrol leaks from
the other union the valve is faulty and the
complete filler pipe must be renewed.
Refitting
7Refitting is the reverse of the removal
procedure, noting the following.
a)Check the condition of all hoses and
clips, renewing any components that are
found to be worn or damaged
b)When reconnecting the small-bore vent
hoses to the unions at the pipe’s upper
end, connect the hose from the charcoal
canister to the uppermost union and the
vent hose from the tank itself to the lower
union (see illustration).
c)Replacing any that were cut on removal
use the clips or ties provided to secure
any other pipes or hoses to the filler pipe.
d)Check carefully for signs of leaks on
refilling the tank; if any signs of leakage
are detected, the problem must be
rectified immediately.
16Fuel tank - removal and
refitting
4
Note: Refer to Section 2 before proceeding
Removal
SOHC models
1The procedure is similar as for models with
carburettors. Refer to Chapter 4A, however
note the following:
a)Depressurise the fuel system (Section 8).
b)On models with C16 NZ and X16 SZ
engines, disconnect the exhaust system
from the manifold.
c)When working on the fuel tank sender
unit, note that there is only one hose to be
disconnected.
Fuel and exhaust systems - fuel injection models 4B•7
15.7 Vent hose connections at fuel tank
filler pipe
A Charcoal canister hose
B Tank vent hose
13.3 Fuel pump - ‘in-tank’, fuel pump
model
A Wiring connector
B Fuel hose clampC Mounting bracket
screws
12.8 Fuel pump clamping sleeve should
rest against rim (arrowed)

d)Disconnect the fuel pump hose and wiring
as described in Section 12.
e)When releasing the tank mounting straps,
note that the fuel filter must either be
moved aside or removed completely,
whichever is most convenient
f)One of the fuel hoses connects to a pipe
in the side of the tank.
DOHC models
2Disconnect the battery negative lead.
3Siphon out any remaining fuel in the tank
through the filler pipe. Siphon the fuel into a
clean metal container that can be sealed.
4Chock the front wheels, then jack up the
rear of the vehicle, and support on axle stands
placed under the body side members (see
“Jacking and Vehicle Support”).
5Open the fuel filler flap, then pull back the
rubber seal to expose the fuel filler pipe
securing screw (see illustration). Remove the
screw.
6Release the fuel tank vent hoses from the
clips on the underbody.
7Support the weight of the fuel tank on a
jack, with an interposed block of wood.
8Unscrew the securing bolts from the tank
mounting straps. Then remove the straps and
lower the tank sufficiently to enable the fuel
hoses, vent hoses and fuel tank sender unit
wiring to be disconnected (see illustration).
9Disconnect the vent hoses and the fuel tank
sender unit wiring. Note the positions of the
vent hoses as an aid to refitting.
10Disconnect the fuel hoses from the tank and
the fuel tank sender unit, making a note of the
hose positions for use when refitting. Be
prepared for fuel spillage, and take adequate fire
precautions. Plug the open ends of the hoses, to
prevent dirt ingress and further fuel loss.
11Lower the fuel tank, and withdraw it from
under the vehicle.
12If the tank contains sediment or water, it
may be cleaned out using two or three rinses
with clean fuel. Shake vigorously using
several changes of fuel, but before doing so,
remove the fuel tank sender unit, as described
in Section 17. This procedure should be
carried out in a well-ventilated area, and it is
vital to take adequate fire precautions - refer
to the “Safety first!” Section at the beginning
of this manual for further details.
Refitting
13Any repairs to the fuel tank should be
carried out by a professional.
14Refitting is a reversal of removal, ensuring
that all hoses are reconnected to their correct
locations as noted during removal.
15On completion, fill the fuel tank, then run
the engine and check for leaks. If leakage is
evident, stop the engine immediately, and
rectify the problem without delay.
17Fuel tank sender unit -
removal and refitting
3
Note:Refer to Section 2 before proceeding
Removal
SOHC models
1Remove the fuel tank, (refer to Section 16),
if necessary. Note that there is only one hose
connected to the sender unit. This must also
be disconnected from the union on the inside
of the unit before it can be withdrawn
completely from the tank (see illustration).
DOHC models
2Remove the fuel tank, as described in
Section 16.
3Make alignment marks on the sender unit
and the fuel tank so that the sender unit can
be refitted in its original position.
4To remove the sender unit, an improvised
tool must be used which engages with thecut-outs in the sender unit retaining ring. The
Vauxhall special tool KM-673 for this purpose
is shown (see illustration).
5Withdraw the unit carefully, to avoid
bending the float arm.
6Recover the sealing ring.
Refitting
7Refitting is a reversal of removal,
remembering the following points.
8Renew the sealing ring.
9Ensure that the marks made on sender unit
and fuel tank before removal are aligned.
10Refit the fuel tank, (Section 16).
18Fuel flow damper - removal
and refitting
3
Note:Refer to Section 2 before proceeding
Removal
1The fuel flow damper is located on the fuel
pump bracket under the rear of the vehicle, on
the right-hand side of the spare wheel well or
in front of the fuel tank, depending on model
(see illustration). The damper is positioned in
the fuel feed line between the fuel pump and
the fuel filter, and its purpose is to reduce
pressure fluctuations in the fuel return line,
thus reducing noise levels.
2Disconnect the battery negative lead.
3Have a container to hand, to catch the fuel
that will be released as the damper is
removed.
4B•8Fuel and exhaust systems - fuel injection models
16.5 Fuel filler pipe securing screw
(arrowed) - models with semi-trailing arm
rear axles17.1 Fuel level sender unit - models with
semi-independent rear axles
18.1 Fuel flow damper - models with semi-
trailing arm rear axles17.4 Vauxhall special tool KM-673 for
removing fuel level sender units
16.8 Fuel tank mounting - models with
semi-trailing arm rear axles
1 Strap securing bolt 2 Vent hose securing

4B
4Clamp the fuel hoses on either side of the
damper, to minimise fuel loss when the hoses
are disconnected.
5Loosen the clamp screws, and disconnect
the fuel hoses from the damper. Be prepared
for fuel spillage, and take adequate fire
precautions.
6Unscrew the securing nut, and withdraw
the damper from the bracket.
Refitting
7Refitting is a reversal of removal.
8Run the engine and check for leaks on
completion. If leakage is evident; stop the
engine immediately, and rectify the problem
without delay.
19Throttle cable - removal,
refitting and adjustment
3
Removal
1This procedure is basically the same as
described in Chapter 4A, but note the
following.
2Not all models are fitted with an air box.
Ignore references to it, if not applicable.
3For “carburettor” substitute “throttle body”,
and note that the cable bracket is bolted to
the inlet manifold.
4The throttle cable end may connect to a
balljoint on the throttle valve lever, which is
retained by a clip (see illustration).
5If fitted, remove the air box. Refer to
Section 5, if necessary.
6Where fitted, use a pair of needle-nosed
pliers to extract the wire spring clip securing
the cable end balljoint to the throttle linkage.
Prise the cable end off the linkage.
7Withdraw the clip and pull the cable outer
seating grommet out of the cable bracket,
then release the cable as far as the bulkhead
(see illustration).
8Working inside the passenger
compartment, remove the driver’s footwell
trim panel, refer to Chapter 11, if necessary.
9Release the end of the cable’s inner wire
from the “keyhole” fitting at the top of the
throttle pedal by easing back the spring and
prising the cable end out of the slot.10Prise the grommet out of the bulkhead
and tie a length of string to the cable.
11Noting carefully its routing, withdraw the
cable through the bulkhead into the engine
compartment; untie the string, leaving it in
place, when the pedal end of the cable
appears.
Refitting
12Refitting is the reverse of the removal
procedure, noting the following points.
a)First ensure that the cable is correctly
routed, then draw it through the bulkhead
aperture using the string.
b)Ensure that the bulkhead grommet is
correctly seated.
c)Connect the cable end to the throttle
linkage. Seat the cable outer grommet in
the bracket and pull it through so that the
cable inner wire is just taut when the
throttle linkage is held fully closed. Fit the
clip to secure the cable outer in that
position.
d)Check the throttle operation and cable
adjustment, as described below.
Adjustment
13Refer to Chapter 4A, but for “carburettor”
substitute “throttle body”. If applicable, the air
box must be removed.
14First check that the pedal is at a
convenient height for the driver. This setting
can be adjusted by turning the pedal stop
screw (it will be necessary to remove the
footwell trim panel to reach the screw).
Remember that the pedal must be left with
enough travel for the throttle valve to open
fully. Also check that the pedal pivot bushes
are in good condition.
15Returning to the engine compartment,
check that the linkage pivots and balljoints are
unworn and operate smoothly throughout
their full travel. When the throttle valve is fully
closed and the throttle pedal is released, there
should be hardly any free play in the cable
inner wire.
16If adjustment is required, extract the clip
securing the cable outer seating grommet in
the cable bracket and replace it in the
appropriate groove, so that the cable outer is
repositioned correctly.17With an assistant operating the throttle
pedal from the driver’s seat. Check that when
the pedal is fully depressed, the throttle valve
is fully open. If there is insufficient pedal travel
to permit this, unscrew the pedal stop screw,
then reset the cable at the throttle linkage.
18When cable adjustment is correct, refit all
disturbed components.
20Idle mixture - checking and
adjustment
3
Note: No adjustment of idle mixture is
possible on models fitted with a catalytic
converter, and no adjustment of idle speed is
possible with the Motronic system. Refer to
Section 2 before proceeding. A tachometer
and an exhaust gas analyser (CO meter) will be
required to carry out adjustment on models
fitted with Motronic systems.
Multec systems
Checking
1If the CO level reading is incorrect (or if any
other symptom is encountered which causes
you to suspect a fault) always check first that
the air cleaner element is clean. Check also
that the spark plugs are in good condition and
correctly gapped. Ensure that the engine
breather and vacuum hoses are clear and
undamaged. Check that there are no leaks in
the air inlet trunking. Check the throttle body
and the manifolds for damage. Ensure that the
throttle cable is correctly adjusted (see Section
19). If the engine is running very roughly, check
the compression pressures (Chapter 2A) and
remember the possibility that one of the
hydraulic tappets might be faulty, producing
an incorrect valve clearance. Check also that
all wiring is in good condition, with securely
fastened connectors. Check that the fuel filter
has been renewed at the recommended
intervals and that the exhaust system is
entirely free of air leaks which might upset the
operation of the catalytic converter, if fitted.
Adjustment
2The idle mixture is controlled entirely by the
ECU and there is no provision at all for any
form of adjustment. Furthermore, accurate
checking is not possible without the use of
Vauxhall test equipment in conjunction with a
good-quality, carefully calibrated exhaust gas
analyser.
3While it may be possible for owners with
access to such analysers to check the
mixture, the results should be regarded as no
more than a rough guide. If the mixture is
thought to be incorrect, the vehicle should be
taken to a Vauxhall dealer for checking. If the
CO level exceeds the specified value the
system must be checked thoroughly by an
experienced mechanic using the Vauxhall test
equipment until the fault is eliminated and the
defective component renewed.
Fuel and exhaust systems - fuel injection models 4B•9
19.7 Throttle cable end grommet in
bracket on inlet manifold19.4 Disconnecting the throttle cable end
from the throttle valve lever - SOHC model