Peugeot 405. Manual - part 36

25 To remove a fuel injector from the fuel rail,
carefully remove the metal securing clip, then
pull the injector from the rail. Be prepared for
fuel spillage.
26 Refitting is a reversal of removal, but use
new injector O-rings.

Fuel pressure regulator

Note: Refer to the warning note in Section 1
before proceeding.
27 For improved access to the regulator
lower securing nut, remove the fuel rail.
28 If not already done, disconnect the
vacuum hose from the top of the pressure
regulator.
29 Slacken the hose clip, and disconnect the
fuel return hose from the bottom of the
pressure regulator. Be prepared for fuel
spillage.
30 Unscrew the two bolts securing the
pressure regulator to the fuel rail bracket
assembly, whilst counterholding the nuts.
Note that on some models a hose bracket is
secured by the upper bolt.
31 Pull the regulator from the end of the fuel
rail, and recover the O-ring.
32 Refitting is a reversal of removal, but use a
new O-ring when refitting the pressure
regulator to the fuel rail, and where applicable,
use new injector O-rings.

Oxygen sensor

33 The sensor is located in the exhaust
downpipe. When handling the sensor, note
that it is fragile; take care not to drop it, and
do not allow it to contact fuel or silicone
substances.
34 Start the engine and run it until it reaches
normal operating temperature, then switch off
and disconnect the battery negative lead.
35 If access is required from below, jack up
the front of the car and support it on axle
stands (see “Jacking and Vehicle Support).
36 Release the securing clips, and separate
the two halves of the sensor wiring connector.
37 Using a suitable spanner, unscrew it from
the exhaust downpipe.
38 Refitting is a reversal of removal, bearing
in mind the following points.

a) Apply anti-seize compound to the threads

of the sensor.

b) The sensor must be tightened securely;

this will require the use of either a deep
socket, slotted to allow for the sensor
wiring, or of a spanner.

16 Bosch Motronic system

components - removal,
refitting and adjustments

3

Fuel rail and injectors

Note: Refer to the warning note in Section 1
before proceeding. If a faulty injector is
suspected, before condemning the injector, it
is worth trying the effect of one of the
proprietary injector-cleaning treatments.

1 Disconnect the battery negative terminal.
2 Disconnect the vacuum pipe from the fuel
pressure regulator, then slacken and remove
the retaining nut and bolt and release the
wiring/hose retaining clip from the end of the
fuel rail.
3 Bearing in mind the information given in
Section 7, slacken the retaining clips and
disconnect the fuel feed and return hoses
from the fuel rail. Where the original crimped-
type Peugeot hose clips are still fitted, cut
them and discard; replace them with standard
worm-type hose clips on refitting.
4 Depress the retaining tangs and disconnect
the wiring connectors from the four injectors.
5 Slacken and remove the fuel rail retaining
bolts and nuts, then carefully ease the fuel rail
and injector assembly out from the inlet
manifold and remove it from the vehicle.
Remove the O-rings from the end of each
injector and discard them; they must be
renewed whenever they are disturbed.
6 Slide out the retaining clip(s) and remove
the relevant injector(s) from the fuel rail.
Remove the upper O-ring from each disturbed
injector and discard; all disturbed O-rings
must be renewed.
7 Refitting is a reversal of the removal
procedure, noting the following points.

a) Fit new O-rings to all disturbed injector

unions.

b) Apply a smear of engine oil to the O-rings

to aid installation, then ease the injectors
and fuel rail into position ensuring that
none of the O-rings are displaced.

c) On completion, start the engine and

check for fuel leaks.

Fuel pressure regulator

Note: Refer to the warning note in Section 1
before proceeding.
8 Disconnect the vacuum pipe from the
regulator. Note that access to the regulator is
poor with the fuel rail in position, if necessary,
remove the fuel rail as described earlier, then
remove the regulator.
9 Place a wad of rag over the regulator, to
catch any fuel spray which may be released,
then remove the retaining clip and ease the
regulator out from the fuel rail.
10 Refitting is a reversal of the removal
procedure. Examine the regulator seal for
signs of damage or deterioration and renew if
necessary.

Throttle potentiometer

11 Disconnect the battery negative terminal.
12 Depress the retaining clip and disconnect
the wiring connector from the throttle
potentiometer.
13 Slacken and remove the two retaining

screws, then disengage the potentiometer
from the throttle valve spindle and remove it
from the vehicle.
14 Refitting is a reversal of the removal
procedure ensuring that the potentiometer is
correctly engaged with the throttle valve
spindle.

Electronic Control Unit (ECU)

15 Refer to Section 13.

Idle speed auxiliary air valve

16 The auxiliary air valve is mounted onto the
underside of the inlet manifold.
17 To remove it, first disconnect the battery
negative terminal.
18 Depress the retaining clip and disconnect
the wiring connector from the air valve.
19 Slacken the retaining clips and disconnect
both vacuum hoses from the end of the
auxiliary air valve.
20 Slide the valve out from its mounting
rubber and remove it from the engine
compartment.
21 Refitting is a reversal of the removal
procedure. Examine the mounting rubber for
signs of deterioration and renew it if
necessary.

Manifold absolute pressure
(MAP) sensor

22 The MAP sensor is situated on the right-
hand side of the engine compartment where it
is mounted onto the wing valance. To remove
it, first disconnect the battery negative
terminal.
23 Undo the retaining nut and free the MAP
sensor from the body.
24 Disconnect the wiring connector and
vacuum hose and remove the MAP sensor
from the engine compartment.
25 Refitting is the reversal of the removal
procedure.

Coolant temperature sensor

26 Refer to Chapter 3.

Inlet air temperature sensor

27 The inlet air temperature sensor is
screwed into the top of the air cleaner
housing. To remove the sensor first
disconnect the battery negative terminal.
28 Disconnect the wiring connector, then
unscrew the sensor and remove it from the
vehicle.
29 Refitting is the reversal of removal.

Crankshaft sensor

30 The crankshaft sensor is situated on the
front face of the transmission clutch housing.
31 To remove the sensor, first disconnect the
battery negative terminal.
32 Trace the wiring back from the sensor to
the wiring connector and disconnect it from
the main harness.
33 Prise out the rubber grommet, then undo
the retaining bolt and withdraw the sensor
from the transmission.
34 Refitting is reversal of the removal

Fuel/exhaust systems - multi-point fuel injection models  4C•9

4C

Warning: During the procedure
described in this Section it is
very important not to allow fuel
to spill into the engine,

otherwise a hydraulic lock may occur
causing extensive engine damage.

procedure ensuring that the sensor retaining
bolt is securely tightened and the grommet is
correctly seated in the transmission housing.

Fuel injection system relay unit

35 The relay unit is mounted onto the rear of
the ECU plastic box which is situated directly
behind the battery.
36 To remove the relay unit, first disconnect
the battery.
37 Undo the retaining nut, then disconnect
the wiring connector and remove the relay unit
from the vehicle.
38 Refitting is the reverse of removal,
ensuring that the relay unit is securely clipped
in position.

17 Magneti Marelli system

components - removal,
refitting and adjustments

3

1.8 litre models

Fuel injectors

Note: Refer to the warning note in Section 1
before proceeding. If a faulty injector is
suspected, before condemning the injector, it
is worth trying the effect of one of the
proprietary injector-cleaning treatments.
1 Disconnect the battery negative terminal.
2 Remove the air cleaner-to-throttle housing
duct as described in Section 2.
3 Undo the two bolts securing the wiring tray
to the top of the manifold, and position the
tray clear of the injectors.
4 Depress the retaining clip(s) and disconnect
the wiring connector(s) from the injector(s).
5 Slacken the retaining screw and remove the
injector retaining plate; Nos 1 and 2 injectors
are retained by one plate, Nos 3 and 4 by
another.
6 Place a wad of clean rag over the injector,
to catch any fuel spray which may be
released, then carefully ease the relevant
injector(s) out of the manifold. Remove the O-
rings from the end of each disturbed injector,
and discard them - these must be renewed
whenever they are disturbed.
7 On refitting the injectors, fit new O-rings to
the end of each injector. Apply a smear of
engine oil to the O-ring, to aid installation,
then ease the injector(s) back into position in
the manifold.
8 Ensure each injector connector is correctly
positioned, then refit the retaining plate and
securely tighten its retaining screw.
Reconnect the wiring connector(s) to the
injector(s).
9 Refit the wiring tray to the top of the
manifold and securely tighten its retaining
bolts.
10 Refit the air cleaner-to-throttle body duct
and reconnect the battery. Start the engine
and check the injectors for signs of leakage.

Fuel pressure regulator

11 Refer to Section 13.

Throttle potentiometer

12 The throttle potentiometer is fitted to the
right-hand side of the throttle housing. To
remove the potentiometer, first disconnect the
battery negative terminal.
13 Depress the retaining clip and disconnect
the potentiometer wiring connector.
14 Slacken and remove the two retaining
screws, and remove the potentiometer from
the throttle housing.
15 Refitting is the reverse of removal,
ensuring that the potentiometer is correctly
engaged with the throttle valve spindle.

Electronic Control Unit (ECU)

16 Refer to Section 13.

Idle speed control stepper motor

17 The idle speed control stepper motor 
is located on the front of the throttle 
housing assembly. Before removing the
motor, first disconnect the battery negative
terminal.
18 Release the retaining clip and disconnect
the wiring connector from the motor.
19 Slacken and remove the two retaining
screws, and withdraw the motor from the
throttle housing.
20 Refitting is a reversal of the removal
procedure.

Manifold absolute pressure (MAP)
sensor

21 Refer to Section 13.

Coolant temperature sensor

22 Refer to Chapter 3.

Inlet air temperature sensor

23 The inlet air temperature sensor is located
in the throttle housing.
24 To remove the sensor, first remove the
throttle potentiometer as described in
paragraphs 12 to 14.
25 Depress the retaining clip and disconnect
the wiring connector from the air temperature
sensor.
26 Remove the screw securing the sensor
connector to the top of the throttle housing,
then carefully ease the sensor out of position
and remove it from the throttle housing.
Examine the sensor O-ring for signs of
damage or deterioration, and renew if
necessary.
27 Refitting is a reversal of the removal
procedure, using a new O-ring where
necessary, and ensuring that the throttle
potentiometer is correctly engaged with the
throttle valve spindle.

Crankshaft sensor

28 Refer to Section 13.

Fuel injection system relay unit

29 Refer to Section 13.

Throttle housing heating element

30 The throttle housing heating element is
fitted to the top of the throttle housing. To
remove the element, first disconnect the
battery negative terminal.

31 Depress the retaining tangs and
disconnect the wiring connector from the
heating element.
32 Undo the screw(s) securing the wiring
connector to the throttle housing, then
displace the connector and carefully withdraw
the heating element from the throttle housing
(see illustration). Examine the element O-ring
(where fitted) for signs of damage or
deterioration, and renew if necessary.
33 Refitting is a reversal of the removal
procedure, taking great care to ensure that
the element wiring does not become trapped
as the wiring connector bolt(s) are tightened.

2.0 litre models

Fuel rail and injectors

Note: Refer to the warning note in Section 1
before proceeding. If a faulty injector is
suspected, before condemning the injector, it
is worth trying the effect of one of the
proprietary injector-cleaning treatments.
34 Disconnect the battery negative terminal.
35 Remove the air cleaner-to-throttle housing
duct, using the information in Section 2.
36 Disconnect the vacuum pipe from the fuel
pressure regulator.
37 Release the retaining clip and free the
various hoses from the top of the fuel rail.
38 Bearing in mind the information given in
Section 7, slacken the retaining clip, and
disconnect the fuel feed and return hoses
from the ends of the fuel rail. Where the
original crimped-type Peugeot hose clips are
still fitted, cut them off and discard them; use
standard worm-drive hose clips on refitting.
39 Depress the retaining clips and
disconnect the wiring connectors from the
four injectors.
40 Slacken and remove the three fuel rail
retaining bolts, then carefully ease the fuel rail
and injector assembly out from the inlet
manifold, and remove it from the vehicle.
Remove the O-rings from the end of each
injector and discard them; these must be
renewed whenever they are disturbed.
41 Slide out the retaining clip(s) and remove
the relevant injector(s) from the fuel rail.
Remove the upper O-ring from each injector
as it is removed, and discard it; all O-rings
must be renewed once they have been
disturbed.

4C•10 Fuel/exhaust systems - multi-point fuel injection models

17.32  Throttle housing heating element

42 Refitting is a reversal of the removal
procedure, noting the following points:

a) Fit new O-rings to all disturbed injectors.
b) Apply a smear of engine oil to the O-rings

to aid installation, then ease the injectors
and fuel rail into position, ensuring that
none of the O-rings are displaced.

c) On completion, start the engine and

check for fuel leaks.

Fuel pressure regulator

43 Refer to Section 13.

Throttle potentiometer

44 Remove the throttle housing as described
in Section 12.
45 Undo the two retaining screws and
remove the potentiometer from the base of
the throttle housing.
46 On refitting, ensure that the potentiometer
is correctly engaged with the throttle valve
spindle, and securely tighten its retaining
screws.
47 Refit the throttle housing as described in
Section 12.

Electronic control unit (ECU)

48 The ECU is situated inside its own
protective compartment in the battery tray. To
remove the ECU, first disconnect the battery
negative terminal.
49 Unclip the lid from the plastic box and
disconnect the wiring connector from the
ECU.
50 Slide the ECU out of the box and, if
necessary, undo the retaining nuts and
separate it from its mounting plate.
51 Refitting is the reverse of removal,
ensuring that the wiring connector is securely
reconnected.

Idle speed control stepper motor

52 Refer to the information given in
paragraphs 17 to 20 of this Section.

Manifold absolute pressure (MAP)
sensor

53 The MAP sensor is situated on the right-
hand side of the engine compartment,
mounted on the front suspension mounting
turret. To remove the sensor, first disconnect
the battery negative terminal.
54 Undo the three retaining nuts and free the
sensor from the underside of the mounting
bracket.
55 Depress the retaining clip, disconnect the
wiring connector and vacuum hose from the
sensor, and remove the sensor from the
engine compartment.
56 Refitting is a reversal of the removal
procedure.

Coolant temperature sensor

57 Refer to Chapter 3.

Inlet air temperature sensor

58 The inlet air temperature sensor is located
in the base of the throttle housing.
59 To remove the sensor, first remove the
throttle housing as described in Section 12,

then undo the two retaining screws and
remove the throttle potentiometer from the
base of the housing.
60 Trace the wiring back from the sensor to
its wiring connector, and remove the screw
securing the connector to the throttle housing.
61 Carefully ease the sensor out of position,
and remove it from the throttle housing.
Examine the sensor O-ring for signs of
damage or deterioration, and renew if
necessary.
62 Refitting is a reversal of removal, using a
new O-ring where necessary.

Crankshaft sensor

63 Refer to Section 13.

Fuel injection system relay unit

64 Refer to Section 13.

Throttle housing heating element

65 Refer to the information given in
paragraphs 30 to 33 of this Section.

Vehicle speed sensor

66 The vehicle speed sensor is an integral
part of the transmission speedometer drive
assembly. Refer to Chapter 7A for removal
and refitting details.

Knock sensor

67 The knock sensor is screwed onto the
rear face of the cylinder block.
68 To gain access to the sensor, firmly apply
the handbrake, then jack up the front of the
vehicle and support it on axle stands (see
“Jacking and Vehicle Support”). Access to the
sensor can then be gained from underneath
the vehicle.

69 Trace the wiring back from the sensor to
its wiring connector, and disconnect it from
the main loom.
70 Slacken and remove the bolt securing the
sensor to the cylinder block, and remove it
from underneath the vehicle.
71 Refitting is a reversal of the removal
procedure, ensuring that the sensor wiring is
correctly routed and its retaining bolt securely
tightened.

18 Inlet manifold - 

removal and refitting

3

Removal

1 Disconnect the battery negative terminal
and proceed as described under the relevant
sub-heading.

Bosch L3.1-Jetronic system

2 Remove the fuel rail as described
previously. There is no need to disconnect
any fuel hoses. Lay the rail to one side.
3 Disconnect the brake servo vacuum hose
(see illustration).
4 Remove the throttle housing as described
previously.
5 Disconnect and unbolt the ignition coil.
6 Disconnect the supplementary air device air
hose from the manifold (see illustration).
7 Remove the bolt from the starter bracket
(see illustration).
8 Unbolt the oil filler tube support bracket
(see illustration).

Fuel/exhaust systems - multi-point fuel injection models  4C•11

18.8  Oil filler tube support bracket

18.7  Removing the bolt from the 

starter bracket

18.6  Supplementary air device air hose

connection on inlet manifold

18.3  Disconnecting the brake servo

vacuum hose

4C

9 Remove the manifold securing bolts and
the two 5 mm Allen bolts (a long Allen key is
required).
10 Lift off the manifold.

Bosch LU2-Jetronic, Motronic and
Magneti Marelli systems

11 The procedure is similar to that described
above, noting the following points.

a) Note that vacuum, coolant hose and

wiring connections to the manifold and
associated components vary depending
on model. When disconnecting any pipes,
hoses, or wires, take note of their
locations to ensure correct refitting.

b) Where applicable, ignore the references

to the coil, supplementary air device
and/or starter bracket.

c) Ensure that any disturbed gaskets are

renewed.

d) Note that not all manifolds are secured by

Allen bolts.

Refitting

12 Refitting is a reversal of removal using a
new gasket/seal or jointing compound as
necessary. Ensure that the locating dowels
are in position and tighten all bolts to their
specified torque (see illustrations).
Note: The engine gasket kit contains gaskets
for both carburettor and injection type
manifolds. The injection type gasket has cut-
outs for the injector ports. Ensure that the
correct gasket is fitted. The carburettor type
will partially obstruct the injector ports causing
erratic running and loss of power.

19 ACAV inlet system (16-valve

models) - general information,
removal and refitting

3

General information

1 To ensure optimum efficiency at high
engine speeds, and maximum torque at lower
engine speeds, 16-valve models have an inlet
manifold with a variable inlet tract system. The
system is called ACAV (variable acoustic
characteristic induction).
2 The inlet manifold is divided into two tracts
of different length and diameter; a long tract
(for low-speed torque) which is 650 mm long,
diameter 36 mm, and a short tract (for high-
speed power) which is 370 mm long, diameter
45 mm.
3 Situated between the manifold and the
cylinder head is a line of four butterfly valves,
mounted in an alloy housing. Mounted on
either end of the housing is a vacuum
diaphragm assembly. Each diaphragm is
connected to the butterfly valve spindles via a
pushrod. The vacuum diaphragms are
connected to an electrically-operated
solenoid valve, which is in turn connected to
the braking system vacuum pump. The pump
is mounted on the end of the cylinder head,
and is driven off the left-hand end of the inlet
camshaft.
4 At engine speeds below 1800 rpm and
above 5080 rpm, the ECU closes the solenoid
valve, shutting off the vacuum supply to the
diaphragms, and the butterfly valves are

closed. With the valves closed, the short inlet
tracts are closed, and the incoming air flows
only through the long inlet tract, boosting the
torque output.
5 At engine speeds between 1800 rpm and
5080 rpm, the ECU opens the solenoid valve.
The vacuum present in the pump is then
allowed to act on the vacuum diaphragms,
which draws the pushrods into the diaphragm
bodies, and opens up the four butterfly valves.
With the valves open, the incoming air is
allowed to flow through both the short and
long inlet tracts, for maximum power.
6 To check the system, start the engine and
allow it to idle. Slowly increase the engine
speed, whilst observing the vacuum
diaphragm pushrods. At approximately 1800
rpm, the pushrods should be drawn into the
diaphragm bodies (valves open). Release the
throttle cam, and allow the engine to idle
again; the pushrods should extend from the
diaphragms (valves closed).
7 To check the operation of the solenoid
valve, disconnect the vacuum pipe from the
diaphragm. Start the engine, and allow it to
idle. Place your finger over the end of the
pipe; no vacuum should be present in the
pipe. Slowly increase the engine speed; at
approximately 1800 rpm, vacuum should be
felt in the pipe. Allow the engine to idle again,
and check that the vacuum supply is switched
off. If this is not the case, either the solenoid
valve or its supply voltage is at fault.
8 To check the operation of either vacuum
diaphragm assembly, disconnect the vacuum
pipe, and suck hard at the control valve stub;
the pushrod should be drawn into the
diaphragm body, and the valve should open.
If this is not the case, the vacuum diaphragm
is faulty.

Removal and refitting

ACAV valve assembly

9 Remove the inlet manifold as described in
Section 18.
10 Bearing in mind the information given in
Section 7, slacken the retaining clip, and
disconnect the fuel feed and return hoses
from their unions on the fuel rail. Where the
original crimped-type Peugeot hose clips are
still fitted, cut them off and discard them; use
standard worm-drive hose clips on refitting.
11 Depress the retaining tangs, and
disconnect the wiring connectors from the
four injectors. To avoid the possibility of the
wiring connectors being incorrectly
reconnected on refitting, mark each
connector with its relevant cylinder number
(No 1 is at the transmission end of the engine).
12 Disconnect the vacuum hoses from the
fuel pressure regulator and the ACAV
diaphragm hose T-piece.
13 Slacken and remove the nuts and three
bolts securing the valve assembly to the
cylinder head, then slide the assembly off its
mounting studs and remove it from the engine
compartment. Remove the valve assembly

4C•12 Fuel/exhaust systems - multi-point fuel injection models

18.12a  Applying jointing compound to the

inlet manifold

18.12c  Fitting the inlet manifold

18.12d  Tightening the manifold 

securing bolts

18.12b  Ensure locating dowels (arrowed)

are in position