Peugeot 405. Manual - part 32

1

General information and
precautions

The fuel system consists of a fuel tank

(which is mounted under the rear of the car,
with an electric fuel pump immersed in it), a
fuel filter, fuel feed and return lines, and the
throttle body assembly (which incorporates
the single fuel injector and the fuel pressure
regulator). In addition, there is an Electronic
Control Unit (ECU) and various sensors,
electrical components and related wiring. The
air cleaner contains a disposable paper filter
element, and incorporates a flap valve air
temperature control system. This allows cold
air from the outside of the car and warm air
from around the exhaust manifold to enter the
air cleaner in the correct proportions.

Refer to Section 7 for further information on

the operation of each fuel injection system,
and to Section 18 for information on the
exhaust system.

Throughout Part B, it is occasionally

necessary to identify vehicles by their engine
codes rather than by engine capacity. Refer to
the relevant Part of Chapter 2 for further
information on engine code identification.

Note: Residual pressure will remain in the

fuel lines long after the vehicle was last used.
When disconnecting any fuel line, first
depressurise the fuel system as described in
Section 8.

2

Air cleaner assembly and
inlet ducts - removal and
refitting

2

Refer to Chapter 4A, Section 2, substituting

“throttle body” for all references to the
carburettor.

3

Air cleaner air temperature
control system - information
and component renewal

2

Refer to Chapter 4A, Section 3, substituting

“throttle body” for all references to the
carburettor.

4

Accelerator cable - removal,
refitting and adjustment

2

Note: For automatic transmission models
refer to Chapter 7B.

Removal and refitting

1 Refer to Chapter 4A, Section 7 substituting
“throttle body” for all references to the
carburettor. Adjust the cable as described
below.

Adjustment

2 Remove the spring clip from the accelerator
outer cable then, ensuring that the throttle
cam is fully against its stop, gently pull the
cable out of its grommet until all free play is
removed from the inner cable.
3 With the cable held in this position, ensure
that the flat washer is pressed securely
against the grommet, then fit the spring clip to
the third outer cable groove visible in front of
the rubber grommet and washer (see
illustration). This will leave a fair amount of
freeplay in the inner cable which is necessary
to ensure correct operation of the idle control
stepper motor (see Section 14).

4 Have an assistant depress the accelerator
pedal and check that the throttle cam opens
fully and returns smoothly to its stop.

5

Accelerator pedal - 
removal and refitting

2

Refer to Chapter 4A, Section 8.

6

Unleaded petrol - general
information and usage

Note: The information given in this Chapter is
correct at the time of writing. If updated
information is thought to be required, check
with a Peugeot dealer. If travelling abroad,
consult one of the motoring organisations (or a
similar authority) for advice on the fuel
available.

The fuel recommended by Peugeot is given

in the Specifications Section of this Chapter,
followed by the equivalent petrol currently on
sale in the UK.

All Peugeot 405 single-point injection

models are designed to run on fuel with a
minimum octane rating of 95 (RON). All
models are equipped with catalytic
converters, and therefore must be run on
unleaded fuel only. Under no circumstances
should leaded (UK “4-star”) fuel be used, as
this may damage the catalytic converter.

Super unleaded petrol (98 octane) can also

be used in all models if wished, though there
is no advantage in doing so.

7

Fuel injection systems -
general information

Note: The fuel injection ECU is of the “self-
learning” type, meaning that as it operates, it
also monitors and stores the settings which
give optimum engine performance under all
operating conditions. When the battery is
disconnected, these settings are lost and the
ECU reverts to the base settings programmed
into its memory at the factory. On restarting,
this may lead to the engine running/idling
roughly for a short while, until the ECU has re-
learned the optimum settings. This process is
best accomplished by taking the vehicle on a
road test (for approximately 15 minutes),
covering all engine speeds and loads,
concentrating mainly in the 2500 to 3500 rpm
region.

Fenix 1B system

1 The Fenix 1B system is an integrated
single-point fuel injection/ignition system.
Using inputs from various sensors, the
electronic control unit computes the optimum
fuel injector pulse duration, and ignition
advance setting, to suit the prevailing engine
operating conditions.
2 The electronic control unit receives signals
from the following sensors.

a) Engine speed/position sensor.
b) Manifold absolute pressure (MAP) sensor.
c) Inlet air temperature sensor.
d) Throttle position sensor.
e) Coolant temperature sensor.
f) Oxygen sensor.

3 The fuel injection unit houses the fuel
injector, the fuel pressure regulator, the
throttle position switch, and the idle speed
control valve. The single fuel injector injects
fuel upstream of the throttle valve.
4 Idle speed is controlled by the electronic
control unit, via the idle speed control valve.
5 The oxygen sensor allows the electronic
control unit to control the air/fuel mixture
within very fine limits, to enable the use of a
catalytic converter.
6 All the information supplied to the
electronic control unit is computed and
compared with pre-set values stored in the

4B•2 Fuel/exhaust systems - single-point fuel injection models

4.3  Adjust the accelerator cable as

described in text

Warning: Many of the
procedures in this Chapter
require the removal of fuel lines
and connections, which 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.

module memory, to determine the required
period of injection.
7 The electronic control unit constantly varies
the fuel mixture, engine idle speed, and
ignition timing to provide optimum engine
efficiency under all operating conditions, and
to reduce exhaust gas emissions. The mixture
strength is accurately controlled to maintain it
within the operating limits of the catalytic
converter.

Bosch Monopoint MA3.0 system

8 The Bosch Monopoint MA3.0 engine
management (fuel injection/ignition) system
incorporates a closed-loop catalytic converter
and an evaporative emission control system,
and complies with the latest emission control
standards. The system operates as follows.
9 The fuel pump, immersed in the fuel tank,
pumps fuel from the fuel tank to the fuel
injector, via a filter mounted underneath the
rear of the vehicle. Fuel supply pressure is
controlled by the pressure regulator in the
throttle body assembly. The regulator
operates by allowing excess fuel to return to
the tank.
10 The electrical control system consists of
the ECU, along with the following sensors.

a) Throttle potentiometer - informs the ECU

of the throttle position, and the rate of
throttle opening or closing.

b) Coolant temperature sensor - informs the

ECU of engine temperature.

c) Inlet air temperature sensor - informs the

ECU of the temperature of the air passing
through the throttle body.

d) Lambda sensor - informs the ECU of the

oxygen content of the exhaust gases
(explained in Part D of this Chapter).

e) Microswitch (built into the idle speed

stepper motor) - informs the ECU when
the throttle valve is closed (ie when the
accelerator pedal is released).

f) Crankshaft sensor - informs the ECU of

engine speed and crankshaft position

g) Vehicle speed sensor (fitted to the

gearbox) - informs the ECU of road speed.

11 All the above information is analysed by
the ECU and, based on this, the ECU
determines the appropriate ignition and
fuelling requirements for the engine. The ECU
controls the fuel injector by varying its pulse
width - the length of time the injector is held
open - to provide a richer or weaker mixture,
as appropriate. The mixture is constantly
varied by the ECU, to provide the best setting
for cranking, starting (with either a hot or cold
engine), warm-up, idle, cruising, and
acceleration. Refer to Chapter 5 for further
information on the ignition system.
12 The ECU also has full control over the
engine idle speed, via a stepper motor which
is fitted to the throttle body. The motor
pushrod rests against a cam on the throttle
valve spindle. When the throttle valve is
closed, the ECU uses the motor to vary the
opening of the throttle valve and so controls
the idle speed.

13 The ECU also controls the exhaust and
evaporative emission control systems, which
are described in Part D of this Chapter.
14 If there is an error in any of the readings
obtained from either the coolant temperature
sensor, the inlet air temperature sensor or the
lambda sensor, the ECU enters its back-up
mode. In this event, the ECU ignores the
abnormal sensor signal, and assumes a pre-
programmed value which will allow the engine
to continue running (albeit at reduced
efficiency). If the ECU enters this back-up
mode, the warning light on the instrument
panel will come on, and the relevant fault
code will be stored in the ECU memory.
15 If the warning light comes on, the vehicle
should be taken to a Peugeot dealer at the
earliest opportunity. A complete test of the
engine management system can then be
carried out, using a special electronic
diagnostic test unit which is simply plugged
into the system’s diagnostic connector.

Magneti Marelli G5 
and G6 systems

16 A Magneti Marelli engine management
(fuel injection/ignition) system is fitted to 
1580 cc XU5 engines.
17 The fuel injection side of the system
operates as described in the following
paragraphs. Refer to Chapter 5 for information
on the ignition side of the system.
18 The fuel pump, immersed in the fuel tank,
pumps fuel from the fuel tank to the fuel
injector, via a filter. Fuel supply pressure is
controlled by the pressure regulator in the
throttle body assembly. The regulator
operates by allowing excess fuel to return to
the tank. To reduce emissions and to improve
driveability when the engine is cold, engine
coolant is passed through the manifold and
around the throttle body assembly.
19 The electrical control system consists of
the ECU, along with the following sensors.

a) Manifold absolute pressure (MAP) sensor

- informs the ECU of the load on the
engine (expressed in terms of inlet
manifold vacuum).

b) Crankshaft sensor - informs the ECU of

the crankshaft position and engine speed.

c) Throttle potentiometer - informs the ECU

of the throttle position, and the rate of
throttle opening/closing.

d) Coolant temperature sensor - informs the

ECU of the engine temperature.

e) Fuel/air mixture temperature sensor -

informs the ECU of the fuel/air mixture
charge temperature entering the engine.

f) Lambda (oxygen) sensor - informs the

ECU of the oxygen content of the exhaust
gases (explained in greater detail in Part D
of this Chapter).

20 In addition, the ECU senses battery
voltage (adjusting the injector pulse width to
suit, and using the stepper motor to increase
the idle speed and, therefore, the alternator
output if the voltage is too low). Short-circuit
protection and diagnostic capabilities are

incorporated into the ECU, and it can both
receive and transmit information via the
engine management circuit diagnostic
connector, thus permitting engine diagnosis
and tuning by special diagnostic equipment.
21 All the above signals are compared by the
ECU, using digital techniques, with set values
pre-programmed (mapped) into its memory.
Based on this information, the ECU selects
the response appropriate to those values and
controls the ignition HT coil (see Chapter 5),
and the fuel injector (varying its pulse width -
the length of time the injector is held open - to
provide a richer or weaker mixture, as
appropriate). The mixture, idle speed and
ignition timing are constantly varied by the
ECU, to provide the best settings for cranking,
starting (with either a hot or cold engine),
warm-up, idle, cruising and acceleration.
22 The ECU regulates the engine idle speed
via a stepper motor which is fitted to the
throttle body. The motor has a pushrod
controlling the opening of an air passage
which bypasses the throttle valve. When the
throttle valve is closed, the ECU controls the
movement of the motor pushrod, which
regulates the amount of air which flows
through the throttle body passage, and so
controls the idle speed. The bypass passage
is also used as an additional air supply during
cold starting.
23 The ECU also controls the exhaust and
evaporative emission control systems, which
are described in Part D of this Chapter.
24 If there is an error in any of the readings
obtained from any of the engine management
circuit sensors, the ECU enters its back-up
mode. In this event, the ECU ignores the
abnormal sensor signal, and assumes a pre-
programmed value which will allow the engine
to continue running (albeit at reduced
efficiency). On entering this back-up mode,
the engine management warning light in the
instrument panel will come on, informing the
driver of the fault, and the relevant fault code
will be stored in the ECU memory.
25 If the warning light comes on, the vehicle
should be taken to a Peugeot dealer at the
earliest opportunity. A complete test of the
engine management system can then be
carried out, using a special electronic
diagnostic test unit which is simply plugged
into the system’s diagnostic connector.

8

Fuel injection system -
depressurisation

2

Note: Refer to the warning note in Section 1
before proceeding.

Fuel/exhaust systems - single-point fuel injection models  4B•3

4B

Warning: The following
procedure will merely relieve
the pressure in the fuel system -
remember that fuel will still be

present in the system components, and
take precautions accordingly before
disconnecting any of them.

1 The fuel system referred to in this Section is
defined as the tank-mounted fuel pump, the
fuel filter, the fuel injector and the pressure
regulator in the injector housing, and the
metal pipes and flexible hoses of the fuel lines
between these components. All these contain
fuel which will be under pressure while the
engine is running, and/or while the ignition is
switched on. The pressure will remain for
some time after the ignition has been
switched off, and it must be relieved in a
controlled fashion when any of these
components are disturbed for servicing work.
2 Disconnect the battery negative terminal.
3 Place a suitable container beneath the
connection or union to be disconnected, and
have a large rag ready to soak up any
escaping fuel not being caught by the
container.
4 Slowly loosen the connection or union nut
to avoid a sudden release of pressure, and
position the rag around the connection, to
catch any fuel spray which may be expelled.
Once the pressure is released, disconnect the
fuel line. Plug the pipe ends, to minimise fuel
loss and prevent the entry of dirt into the fuel
system.
5 An alternative method of depressurising the
fuel system is to remove either the fuel pump
fuse or the fuel pump relay and start the
engine. Allow the engine to idle until it stops.
Turn the engine over on the starter once or
twice to ensure that all pressure is released,
then switch off the ignition. Always disconnect
the battery negative lead before carrying out
work on the fuel system, and do not forget to
refit the fuse or relay when work is complete.

9

Fuel pump - 
removal and refitting

2

Note: Refer to the warning note in Section 1
before proceeding. The fuel pump is mounted
either on the outside of the fuel tank (external)
or on the inside of the fuel tank (internal)
according to model.

Removal

External mounted

1 Depressurise the fuel system (Section 8).

2 Disconnect the battery negative lead.
3 Chock the front wheels then jack up the
rear of the vehicle and support on axle stands
(see “Jacking and Vehicle Support”).
4 Disconnect the electrical connections on
the pump (see illustration).
5 Loosen the clips and disconnect the inlet
and outlet fuel hoses.
6 Cut through the plastic cable-tie and slide
the pump from the rubber mounting straps.

Internal mounted

7 For access to the fuel pump, tilt or remove
the rear seat as described in Chapter 11.
8 Using a screwdriver, carefully prise the
plastic access cover from the floor to expose
the fuel pump. The pump is located under the
right-hand cover.
9 Disconnect the wiring connector from the
fuel pump, and tape the connector to the
vehicle body, to prevent it from disappearing
behind the tank (see illustration).
10 Mark the hoses for identification
purposes, then slacken the feed and return
hose retaining clips. Where the crimped-type
Peugeot hose clips are fitted, cut the clips and
discard them; use standard worm-drive hose
clips on refitting. Disconnect both hoses from
the top of the pump, and plug the hose ends.
11 Noting the alignment marks on the tank,
pump cover and the locking ring, unscrew the
ring and remove it from the tank (see
illustration). This is best accomplished by
using a screwdriver on the raised ribs of the
locking ring. Carefully tap the screwdriver to

turn the ring anti-clockwise until it can be
unscrewed by hand.
12 Displace the pump cover, then reach into
the tank and unclip the pump from the tank
base. Lift the fuel pump assembly out of the
fuel tank, taking great care not to damage the
filter, or to spill fuel onto the interior of the
vehicle. Recover the rubber sealing ring and
discard it - a new one must be used on
refitting (see illustrations).
13 Note that the fuel pump is only available
as a complete assembly - no components are
available separately.

Refitting

External mounted

14 Slide the pump into the rubber mounting
straps and secure with a new plastic cable-tie.
15 Reconnect the fuel inlet and outlet hoses.
16 Reconnect the electrical connections.
17 Lower the vehicle to the ground and
reconnect the battery negative lead.
18 Start the engine and check for leaks.

Internal mounted

19 Ensure that the fuel pump pick-up filter is
clean and free of debris. Fit the new sealing
ring to the top of the fuel tank.
20 Carefully manoeuvre the pump assembly
into the fuel tank, and clip it into position in
the base of the tank.
21 Align the mark on the fuel pump cover
with the centre of the three alignment marks
on the fuel tank, then refit the locking ring.
Securely tighten the locking ring, then check

4B•4 Fuel/exhaust systems - single-point fuel injection models

9.11  Unscrew the locking ring . . .

9.12b  . . . and recover the 

rubber sealing ring

9.12a  . . . then lift out 

the fuel pump . . .

9.9  Unplug the wiring connector then

release the fuel feed and return hoses

(arrowed) from the fuel pump

9.4  Fuel pump showing electrical

connections (A) and fuel hoses (B)

that the locking ring, pump cover and tank
marks are all correctly aligned (see
illustration).
22 Reconnect the feed and return hoses to
the top of the fuel pump, using the marks
made on removal to ensure that they are
correctly reconnected, and securely tighten
their retaining clips.
23 Reconnect the pump wiring connector.
24 Reconnect the battery negative terminal
and start the engine. Check the fuel pump
feed and return hoses unions for signs of
leakage.
25 If all is well, refit the plastic access cover.
Tilt or refit the rear seat as described in
Chapter 11 (as applicable).

10 Fuel gauge sender unit -

removal and refitting

3

Refer to Chapter 4A, Section 5, noting that

there where the fuel pump is mounted
externally there are no fuel pipe connections
to the sender unit (see illustration).

11 Fuel tank - 

removal and refitting

3

Refer to Chapter 4A, Section 6, noting that

it will be necessary to depressurise the fuel
system before the feed and return hoses are
disconnected (see Section 8). It will also be

necessary to disconnect the wiring connector
from the internal fuel pump before lowering
the tank out of position.

12 Throttle body - 

removal and refitting

3

Note: Refer to the warning note in Section 1
before proceeding.

Removal

1 Disconnect the battery negative terminal.
2 Remove the air cleaner housing-to-throttle
body duct, using the information given in
Section 2 (see illustration).
3 Depress the retaining clips and disconnect
the wiring connectors from the throttle
potentiometer, the idle control stepper motor

(where fitted), and the injector wiring loom
connector which is situated on the side of the
throttle body (see illustrations).
4 Bearing in mind the information in Section 8
about depressurising the fuel system, release
the retaining clips and disconnect the fuel
feed and return hoses from the throttle body
assembly. If the original crimped-type
Peugeot clips are still fitted, cut the clips and
discard them; use standard worm-drive hose
clips on refitting (see illustration).
5 Disconnect the accelerator inner cable from
the throttle cam, then withdraw the outer
cable from the mounting bracket, along with
its flat washer and spring clip.
6 Disconnect the idle control auxiliary air
valve and/or purge valve hose from the
throttle body (as applicable).
7 Slacken and remove the bolts securing the
throttle body assembly to the inlet manifold,
then remove the assembly along with its
gasket (see illustration).
8 If necessary, with the throttle body
removed, undo the retaining screws and
separate the upper and lower sections, noting
the gasket which is fitted between the two.

Refitting

9 Refitting is a reverse of the removal
procedure, bearing in mind the following
points:

a) Where applicable, ensure that the mating

surfaces of the upper and lower throttle
body sections are clean and dry. Fit a new
gasket and reassemble the two sections,
tightening the retaining screws securely.

Fuel/exhaust systems - single-point fuel injection models  4B•5

12.2  Air cleaner housing-to-throttle body

duct (Magneti Marelli fuel injection system)

12.4  Fuel feed and return hose

connections (arrowed) - later model shown

12.3b  . . . the injector wiring loom

connector and the stepper motor

12.3a  Disconnect the wiring connectors

from the throttle potentiometer . . .

10.1  Removing the fuel gauge sender unit

9.21  On refitting tighten the locking ring

until it is correctly aligned with the fuel

tank mark (arrowed)

4B

12.7  Throttle body retaining screws

(arrowed) on the Bosch Monopoint system