Volvo 240 1989 User manual

Service Manual
Faulttracing Design
Repairs Function
Maintenance
TP 31361/1; 12.88
Se ctio n 2 (2 3)
lH- J etr on ic 2.4
fuel sy stem
E
ngine B 230 F
240 1989-19
..

This manual covers the following:
B 230 F
Gasoline engine wi th fuel injection and catalyt ic con-
erter system.
2.3 titer cylinder volume.
Two valves per cylinder.
LH 2.4 fuel system
To identify the system with certainty, look for the
following item (see illustration):
--
"
Diagnostic socket

Contents
Fuel system LH2.4 - 240
Contents Page
Specifications.. .. ,.,...... .. . ....... 2
Special
tools ..... .. .. ..
. .. 5
Design and function
-System overview ........... .,. ........ .. ~ , ............,..............., ....
... 6
-Control unit ...... ,.... .. .. ...... .. _.... .............. .. , .... .. .... .. 8
-Sensors ......................................................., ............ .. ............ .. ........... 11
-Catalytic converter, pressure regulator.... .........
.. ............ .... ......... .. ... .. .... .. ......... .13
-Injectors, coldlstart valve, fuel pumps. .......... ... ............. ................ .. ...... _.. .. ... ... 14
-Fuel filter, idle valve. .... .. .. .... .. ........_. ......... .. ._ .. .. ...... . ..... .. 15
-System relay, fuses
.. ........ ~ .... . ........._.... ....... .. ..... .......... ... .. ........._..... .. ... 16
- EVAP system....... _. ..... .. ..... . ..... ._ ...... , _ . ... _ ... .. .. .. .......... . . .. 16
-Diagnostic system...... .............. .. ........ __ .............. .. .........._ .. . ............................ 17
Fault tracing, repairs, maintenance
Detailed table of contents ..................
,.18
Wiring diagrams ................. ............ .......... _ .... ..
.. ..... 54
li he first section of this manual covers the Design and
Function of the fuel system, Reading it will provide
the necessary background for understanding the
second section -Fault tracing, Repairs and Mainte-
nance,
Order No.: TP 31361/1
We reserve the right to make alterations
©VOLVO NORTH AMERfCA CORPORATION

Specifications
Fuel system LH2.4 -240
Specifications
Gasoline, unleaded
Octane requirements:
-RON (Researct1 Octane Number)
91 -95
-AKI Rt M ................................87
2
Air mass meter
Volvo PIN
.. 3517020
Bosch PIN.
.. ................. 0280212016
Resistance between connectors
2 and 3
... . .. ..................... 25-4 .0 n
Throttle switch
Volvo PIN .. .................................... 3517068-7
Bosch
PIN .... ....... .. . .. ..........0 2 80120 325
Con lr ol unit (part numbers)
Wilh EGR (California)
Volvo PIN ..................
.. .. ... 3501687-2
Bosch
PIN . ........... ..
.. ... 0 280 000 556
Without EGR (remainder of USA, Europe):
Volvo PIN ............................... .... 3517407-7
Bosch
PIN ........... ....................... 0 280 000 561
0 280 160 ...
Fuel pressure regulator
VolV OPIN ................. .............. .... 3517064-6
Bosch PIN ..................................... 0 280 160 294
Syslem p ressur e (fuel pressure above intake
manifold pressure):
.. .............300 kPa (42 psi)

Specifications
Fuel svstem LH2.4 - 240
t
o 280 150
Injectors
-Volvo PIN ......... .. ....... .. . .
.... 3517572-8
-
Bos ch PIN................... .....
0280150762
Injeclion capacity 214 cm'lmin at 300 kPa (42 psi)
system pressure.
(Note: use
on ly spedal equipment to test disas-
sembled injector)
Cold start valve Icertain models)
Volvo PIN ....................................... 3517130-5
Bosch PIN...............
.. ........... ... 0 280 1 70 264
Injection capa
ci ty around 165 cmJ /min.
~
0580464
Fuel pump
Volvo PIN .......... . .. .. ......... .... .... 1389449-8
Bosch
PIN ...............0 580 464 039
Pumpcapacityal 300 kPa (42 psi) and +20°C ( 68
e
F) :
-12 V .....
.. . .. .. .. .............. .. .. .... 130 liters/hour
1.0 litersl
30 sec
-
11 V ....
.. .. 108 liters/hour
0.8litersl30 sec
-
10 V .. ... .. ....... .. .. .......65 Utersthour
0.6 lilers/30 sec
Current consumption at 300 kPa (42 psi). +20·C
(68 ° F) and 12 V
-ma
xi mum .. ....... ........... .. .. ........... 6.5 amp
Safety screen
Fuel
filter
Volvo PIN .. .. ................ 1389450-6
Filters particles down
to min. of: ... 0.002 IRll
Tightening torque .... .. ......20-35 Nm (15-25 n.I !»
Tank p
ump
Volvo PIN .. ........................ ...... .. . .. 1389721-0
(1317671)
Current consumption .....................
3- 4 amp
3

Specifications
Fuel system LH2.4 240
o
40000
20000
1 0000
8000
60 00
4000
2000
10 00
8 00
600
400
200
100
,
"-
"-
r-...
.....
r-.....
i'-..
- 30 - 20 0 20 40 60 IKt 100 1 20 'C
-22
-4 32 68 104 140 176 212 248 -F
l!!!2!
Idle valve
-Volvo PIN" "
.. , .. ." .. """."",,.,, 1389618-8
-Bosch PIN
."""",, ... ,," ",, 0280140516
Resistance between terminals
1 and 2
"" "" """""" """" """"",,,. 8 n
Coolant temperature sensor
-Volvo PI N. """. "" ." "". "" ,, .,,' ", 1346030-8
-Bosch PIN
,""""" '" ." ,, ' "'' '' ,, 0280130032
Resistance in !ls at:
-10°C (14°F)
"""""" "", ,,,, 826 0- 10560
+20°C (68°F)
... " .. ' '''' '' ''' """.228 0-2720
+80°C (176°F)
",,"""" """" "",290-364
For other values, see chart,
"'
•
Q
1I ~-----!!.!. [) l' JP=.'::::::I
025 8 003 . ..
Lambda-sand
- Vol vo PIN ", """" """ .,, "" " ,3501753-2
-Bosch PIN "" "."" " """ """ " """", 0258 003 034
Resistance pre-heating resistor
-cold sond. +20°C (68°F)
".".,," "" 3 n
-hot sond, over 350°C (660°F) "" ,, 13 n
Tightening torque """." ",55 Nm (40 IUb )
Apply "Never Seez" paste (PIN 1 1
61 035-9) to the
threaded section
01 the sond,
4

~' '''~
; , 1/
"
Special tools
Fuel system LH2.4 240
Special tool s
999-
Description-use
5011-5 Pressure gauge: indicating
fu el pressure.
Use d with 5116, 5265, 5266.
5116-2 Hose:
connecting pressure gauge 5011.
5151-9
Adaptor: CO-meter.
5843-1 V
acuum pump: check ing pressure regu l ator.
6450-4 V
olt Amp meter : f ault tracing.
6525-3 Multimeter: volt, a
mp , ohm. diode.
9724-0
Ohm-diode meter: fault tracing.
9921-0 Volvo Mono-Tester:
sett i ng ignition, idli ng speed.
~
Q
~-'<V
~ ~
~
515 1 --= ~~ -'"
CO
6450
9724
5

Design and Function
LH-Jetronic 2.4 -LH2.4
~ ® C . A ccomp, .. w
ltd A rwlte.h
SV "'" Iii P" I II
fel'Y ! t
[]
1t.Wl
~
Idlell ll i ve @
F ue l J ystam
co ntr ol
unit
" Qia gnosti c
unit
o Th rottle
~ _ W _ ''' _ h ____________ ~
Au mllill /"'::\2
m et er \.V
~
®~'~
~ CIo rt.on
~ml.'
h lomb ...
\) 'ON!
Fuol
hlt_
@)
......
,..mp
RO .""" ~'17'
v .... ~\:.V
Coolant
ro mp _
18 nsor
Prim a ry
pump
®
The circled numbers til the drawing reterto the same
numbers in the following listing,
6

•
De s ign and function
Fuel sy st em LH2.4 - 240
Characteristics of LH2.4 fuel system for Volvo 240:
It is used together with the EZ116K ignition sys-
tem.
It is an adaptive system.being capable of multiple
adjustments based on driving experience.
It is monitored by a self-diagnostic system that
lights up a warning lamp on the instrument panel.
It has a memory capability of up to three fault
codes (Scandinavia/USA Federal) plus seven-
teen additional codes (USA/California). Subse-
quent fault tracing can be carried out
by actively
utilizing the diagnostic program.
It measures intake air mass via air mass meter
supplied with a hot wire.
It utilizesaprima ry pump in the fuel tankand a fuel
pump with fuel filter on the fuel line to the engine.
II works on a fuel pressure of 300 kPa ( 42 psi).
It utilizes a separate cold slart valve which sup-
plies extra fuel at.or below 15°C (60"
F) or cotder.
It provides a richer fuel mixture to counteract
knock when the fuel system's anti-knock control
system has been unsuccesslul at reducing knock
by adjusting downward several degrees.
It requires no adju st ment of CO because of the
adaptive function.
It h as a "limp home" se Mi ng at the idle valve In
caseoflossofcurrent. the idlev
al ve rema in sopen
to provide emergency air intake.
In the USA: It has an integrated shi ft Indicator
refated
to vehicle speed and engine rpm. The
indicatorfamp lights up ifthe rpm for the next gear
are higher th
an the pre-programmed limit s.
-It uses an induction sensor on th e fly whe et to
indicate rpm and c ra nk shaft posi ti on vi a the igni-
tion system control uni
t.
It is fitted with the same mo del Lambda-so nd as
for previous l H fuel
sy stems. The resistance of
the Lam
bd a-sond is affect ed by the eXhaust- gasl
oxygen concentration The Lambda-sond is
mounted on the exhaust manifold between tile
engine and Ihe catalytic conver1er.
It is fi tt ed WIth a three-way catalylJc conver1er.
It utilizes an EVAP system to handle fuel vapors
in the fuel tank.
7

Des ign and function
temperature
sensor
Lambda-
",o d
ctI; ( ~
.A9'J1riJ
~@ff;; ---1 . ~- -
Ttuoule
s wilt:: h
~ -
II
+ -
Ignition
control
Cold surt
h Auxiliary
'- - -W rela'y
Fu el system LH2.4 -2 40
Control unit
The control unit has a microprocess or that receives
signals from the
var ious sensors reg ar ding
operational condition
s, evaluates them in relation to
pre-programmed valuas and calculates the correct
injector opening durations
(in mil/i-seconds p er revo-
lution).
The conlrol unit governs idling rpm by regulating the
amount of aIr by-passing
th e throttle valv e. It also
controls other functions, s
uc h as the cold start valve,
the fuel pump and
th e relay. One impo rt ant function
is monito
ri ng fault fracing via the diagnostic socke t.
Self-adjusting functions
Thecontrol unit is adaptive in that it adjusts it s calcu-
lations according to assimilated input.
Sell-adjusting Idle speed regulation
In time,w ea r and coatings will affect the operation of
the thr
oH le valve, causing less aI r to ent er the intake
system. Instead
01 working from a pre-programmed
value the idle valve receives a signal that is adapted
to theexperiences which the control unit has learned
from previous driving periods.
Self-adjusting Lambda-sand
The Lambda-sond operates in a similar fashion. It
senses if the fuel mixture is rich or lean and adjusts
the control unit's Lambda regulat
or accordingly.
The self-regulatingmechanism keepsthe control unit
function at midpoint. This does away with the
need
to adjust the CO content and automatically compen-
sates for the effects of tolerances and wear
in the in -
jection syste
m.
Whe never th e vehicle is started and driven, the con-
trol unitwill use the value that has been learned from
previous driving periods.
8

Design and function
Fuel system LH2.4 - 240
The control unit microprocessor
receives:
Exhaust gas oxygen content information from the
Lambda-sand.
Rpm and crankshaft
po sition information from the
ignition system control unit. If this information
is
not forthcoming, the fuel system control unit will
not function.
Engine temperature information from the coolant
temperature sensor.
Engine load information from the air mass meter.
Information from the shutter switch as to whether
the
th rottle shutter is closed or wi de open.
El ectrical system voltage from th e battery current.
The signal from the AC switch info
rm s if it is on,
and the signal from the compressor connection
indicates that the compressor is operating.
Emergency program
There is a "limp home" function provided if the signal
from the air mass meter ceases for some reas
on,
such as the hot wi re bu rn ing off. A p re -programmed
value
is used fo r Injection duration, allowing th e
vehicle
to be driven slowly to the garage.
The control unit microprocessor:
Sets the voltage of Ihe sy stem by grounding the
system relay.
Breaks the s ys tem relay ground if engine turns
ova
rtoo slowly (engine has stopped). This keeps
the battery trom being drained and cuts off fuel
fl ow from the fuel pump when the engine isn't in
op eration.
Grounds Ihe injectors, which regulates opening,
liming and injection duration.
Controls air valve tor constant idle speed (CIS).
Is connected to the diagnostic un it and provid es
fault information about the various functions.
Provides the ignition system control unit with load
intormation.
Protects against too high rpm by shutting
oH fuel
injection until the engine has stowed down.
USA/Canada:governs CH ECK ENGINE warning
lamps and shift indicator lamp.
r------------------------------------- ----4 .
r------;:;:;:=~=== ·
~~:~m 8 6 1 2 !Ir-------- 15 I ~ =-- Rpm ..... r-,-d,-.-""""L..J- ---- r:': lJ
Ignition 5Y5tem
control unit
0
.. " .-----'~, I 3 "'-- Full load --. 0 20 I
"' 12 _--, L- _______ _ 21 1 ~
31/ 1"'-- 1 ~ 41'"_ ........ "'Sattery + Throttlll
K - ~ --e lZ I 5 • ; ... . 1 switch
~KIJ !....I ....... • 23 1
~ _ = -I =-O}o 24 1 6 . • 2 . .r=.. ';;~ ="=-=='- :!.~
• 25 1 7 ' • 3 (\'¥-,- -- ,
L. __ Cr&nksh!tfl posit i on _ , \.? __
Shift indicato r n -------e 2ti I 8 I • 4 Ai r m ati Diagno tti,
I,
L...I • 21 1 9 ~ r 5 meter un ' t ... .. . ~ "'
L- _ _ K nock e nflchm6 "' ~ 10 •
S,m., / so 4 ~ 11 ~ - - --- "'- -- '1 --- ~:: " . ~
V 1 12 Coolant b
~ ¥ 30 ,~' AC <omp""'o,
1 13 • . ' _I I tem peratu r lr
Cold start f . 31 1 sensor
~~ ",.. t , 321: :: : ' tAC ' W ~.:.::: : h :' ,. r=;':":'
::..:
:::: ' 1 ':
, . • 331 :r ~
,1 16 ._ \\ ~\. ---+\---+-,
~
:." ~ . ~ :,1 17 :J ~ ~ "' ~ \. ~,
",/ , r- 'E-x.,,- 1 18 k.::.. ....
@
I die waive ---....: -~ --
9

De si gn and function
Fuel system LH2.4 - 240
Th e start- up program provides for two injection
durations per revolution.
The
co ld-sta rt valve is activated when the tem-
perature
is at-15°C(5°F) or below,and th eengine
speedis under
ap proximately 900 rpm. Once the
rpm exceed the pre-programmed limit, the cold-
start valve Is turn
ed off.
======> '"
~ ------------
During nor ma l driving conditions, injection dura-
tion is regulated mos
tl y with referen ce to signals
trom
th e air mass meter.
The choke provides a richer fuel mi xt ure to th e
engine
up to an engine temperature of 60°C
(140"F).
Inj ec ti onduration increases during acceleration.
Knock enrichment provides a ri cher fuel mixture
to cou nt e ra ct kn ock when the fuel system's anti-
knock contr ol system has been unsuccessful at
reducing knock by adjusting downward seve
rat
degrees on all cylinders. Knock cause high
com
bu s ti on temperatures. When knock occurs,
th e control unit increases the amount of fuel in
order bring
th e combus ti on temperature do wn
and reduce th e knock.
Excess rpm
is prevented via a rotation speed
limiter which turns
011 the injectors. They are
turn
ed on again when the engine rotation is re-
du
ce d.
At full load, a ri cher airlluel mixture is used to
provide maximum engine powerand tolessen the
el1ects ofcombustion heat
on th e engine and the
catalytic
co nverter.
During deceleration, fuel injection
is discontin-
ued above 1,800
rpm in all gears. It is resumed at
1,400
to 2,000 rpm, depending on engine tem-
perature.
10

Design and function
Fuel system I.H2.4 - 240
Air mass meter
Measures engine inlake ai r mass. Those factors
whichaffe
ct air densi ty ,such as temp rature,humid·
ity and ptessute (altitude) elc. are laken inlo consId-
eration during measurement.
The measurement sensor insi
de Ihe air mass meter
consists
of a wire which Is maintained at 1 2.0 "C
(2.S0 DF) (previously IOO"C -(215'F ) hig he r tllan tile
ambient air entering the engine. As the air mass
passing over the wire incre
ase s. more currenl is
r
eq uired to maintain the correct te mperature. Th e
amount ofcurrent required Is used to catcula te the air
mass taken
In .
When
th e engine is tu rned oN , any dirt on the wire is
burned oN electrica
ll y by heating the wire to over
1000' C
(tBOO ' F). Any dirt remaining on the wire
would cause it
to send incorrect information to the
co ntrol unitand result In an Incorrect f ueUair mixture.
Protective
grille
Earlier mode
ls of the air mass meter were provided
wi1h an adjustmentscrew for CO seNi ngs. However.
because the
LH2. .4 Lambda-sand is self-adjusting
this screw
is no longer necessary.
o
Coolant temperature sensor
Provides the control unit with information regarding
the engine temperature necessary
fo r pr oper adjust-
ment of injection duration.
11

Design and function
Fuel system LH2.4 - 240
Obt0 09 mount!", bol.- to r
adjunino Iw he h Mtting
Fuili olid
switch ~
Throttle __ --~ ~-"i ~r&2])IS
spindle
C.m disc
Idle switch
(micro SWiTCh)
Heatin':..-.J t...- H-
=
n.m
Sensor
The exhaust gases reach the outer surface of the
Lambda"sond sensor via slits in the protective
sleeve. Ambient air reaches the sensor's inner
surface via channels. The sensor itself consists of a
pfatinum covered zirconium-oxide pipe.
The Lambda-sond signal strength
is in direcf propor-
tion
to the amount of oxygen in the exhaust gases.
Thisdepends
on the airlfuel ratio. ALambdavalue of
1 represents the theoretically perfect ratio. A rich
mixture results in a higher voltage and a lean mixture
gives the opposite result.
The current sent by the Lambda-sond to the control
unit varies between
0.1 and 1.0 volt.
The shift between high and low voltage occurs when
the Lambda value
is at 1. The control unit uses this
information
to adjust the amount of fuel injected.
o
Throttle switch
Tells the fuel system and ignitionsystemcontrol units
whether the throttle valve is closed or fully open.
o
La mbda-sond
Under normal conditions, the optimum mixture ratio
is 14.7kg air
to 1 kg fuel. The ratio is monitored by
post-combustion measurement of the oxygen con-
tent
in the exhaust gas using the Lambda-sond.
This particular model of Lambda-sond is known
as a
"comparing Lambda-sond'. It produces a measure-
able current
by comparing the amount of oxygen in
the exhaust gas with the amount
in the ambient air.
The Larnbda-sondoperatesonly within acertaintem-
perature range -approx. 285-850°
C, (545-1530°F).
It is electrically heated to enable it to reach operat-
ing temperature quickly. When the ignition
is turned
on, current
is sent to a PTC resistor (Positive Tem-
perature Coefficient) whose resistance increases
with rising temperature. Because of this system, the
Lambda-sond quickly reaches correct operating
temperature, even at low exhaust gas temperatures.
The Lambda ·sond is mounted in th e exhaust gas mani-
fold about 15 cm (6 in.) in front of the catalytic co nverter.
12

Design and function
The catatytic converter cleans the exhaust gases in
three
ways :
1 - by incinerating unburned hydrocarbons (HC) at
high temperature, releasing
th e re sidue as
steam (H,O).
2 -
by converting carbon oxide (CO) to carbon dio x-
ide (CO,) through oxidation.
3 -
by reducing nitrogen oxides (NO ,) to gaseous
nitrogen (N).
90
to 95% of the dangerous gases are rendered
hamnless.
o
Di stribution pipe
Theincoming fuel feed line,pressure regulator, injec-
tors and cold start valve are connected
to th e di st ri -
bution pipe.
Fuel system LH2 .4 - 240
Catalytic converter
In order to be able to operate as inte nd ed, th e
catalytic converter
is dependent on correct informa-
tion from the Lambda-sand. The air/
fu el mi xture must
be adjusted so that fuel is completely burned in the
engine prior
to the exhaust gases reaching the cata-
lytic conve
rt er.
The
co nverter can bedamaged through ove rh eating
if unburnt fu el is emitted in th eexhaustwhere oxygen
is present.
This can happen
if a large amount of unburnt fuel
reaches the catalytic converterprior
to starting. It can
also happen if there
is a loose ignition cable, and a
cylinder pumps unburned fuel into the exhaust.
Lead
in the fuel will quickly aHect the La mbda-so nd
and cause the exhaust ga s cleaning function to stop
working.
If tllis happens, th e La mbda-sond wi ll stop
providing the information needed
by the control unit
to set the fuel mixture and the cataly~c oonverterw ill
then be destroyed.
The active area is about 20,000 sq. m (215.000
sq.
ft.). (Cali fo rnia EGR converter approx,32.000 sq. m
~ 34 5,000sq,fl.) Thepreciousmetalcontentisabout
2 grams (.07 oz)
of platinumlrhodlum,
®
Fuel press ure regulator
The fuel pressure regulator ensures t ha t the fuel
pressure remains constant at the
In jectors. Using a
vacuum tube connected
to th e eng in e Intake man i-
fold, the fuel pressure is kept at 300kPa (4 2 psi)
above (below) the intake manifold pressure. In this
way the pressure over the injectors is kepi constant,
regardle
ss of throttle pOSition . The amount of fuel
injected depends entirely
on the Injection duration.
Excess fuel is returned
to th e fuel lank via a return
pipe.
(
13

Design and function
Fuel system LH2.4 - 240
o
o 280 1 50 ...
..
Vi!llv e
pump
Tank
pump
Injectors
The injector is fin ed with a solenoid, a magnetic
actuator and a fuel needte which opens or shuts a
nozzle.
The
control unit feeds c urrent to the injectors
in
ca lculated time units. This ensures that all
the injectors spray a fine fuel mist simultane·
ously.
While
the starter motor is opemting, th e re are two
injeclions p
er rotalion. Th is is reduc ed to one for
norm
al d ri~ i ng. Injectionoccurs in the intake manifold
ne ar the intake ~alves.
Disassembled injectors should only be inspected
using specially designed equipment in order
to mini-
mize the
ri sk of explosion from fhe fu el mist.
Cold start valve ( eenail! mod els)
At cold start, a lot 01 fuel condenses on the cold
surfaces in the lorm of
dr oplels. Having a separate
cold start valve improves cold starting.
It' s placed
farther away from the engine block than the ordinary
injectors and delivers the fuel more as a gas Ihan as
drops. The cold slartvalve
is controlleddirectly by the
conlrol unit, ralher than by the thermal time
swifCh . It
culS in when the temperature is aboul -15cC (5 ° F)
and when Ihe engine rolation is below approx. 900
rpm. It culs out permanently if the rpm exce ed the
permissible limit.
®
Fuel pump
The fuel pumpis an eleclric rollerpump,cooled by the
fuel which flows through
it. It has a non-return valve
and
an overflow valve which opens if the pressure
gels
100 high.
Both
th e primary pump an d Ihe fuel pump operate
wheneither the
st artermotororIheengine is running.
However, should the engine stop while Ihe ignition
remains
on , the conlrol unll wi ll cut off the current to
th e pu mps in order 10 eliminate Ihe risk of fire in Ihe
even! of
an acciden l.
@
Tank pump (pre-pump)
The electric Im peller pump in the fuel tank keeps
pressure in the fuel
lTne prior to the (main) fuel pump
to prevenl vapor lock.
The pump hasa coarse,slralnerIypefilter and anon-
return valveto maintain acertain amounl of pressure
in
th e system even if the main pump is not in
operation.
14

Safety scre8n
When the throNle valve switch is closed during idling,
the control unit receives a signal, enabling
it to send
current
to the air valve electric motor to keep the idle
rpm at the correct level.
Des;gn and funct;ol].
Fu el sys t em LH2.4 - 240
@
Fu el f il ter
The luel filter is adjaoentto the fuel pump and both are
mounted on a plate below the vehicle underthe back
se at.
Itconsistsof apaperfilter and asafety screen to catch
any pieces of the paper filter which come loose.
Idle valve
, In order to set the correct air valve opening and thus
achieve constant idte speed, the control unit uses in-
formation from the air mass meter regarding the
amount of air entering the engine and from the
ignition system control unit regarding rpm. This
means that the idle valve is not affect
ed by air leaks
or a jammed throttle valve.
When the current is off, a spnng sets the idle valve
opening for an idle speed between 1. 000 and 1,100
rpm.
Once the engine
is running, the control unit ensures
that the idle valve is more
or less open al a ll rotation
speeds in order
to preventthedevelopmentofunnec-
essarily high negativepressurein the intakemanifofd
when the throttle shutter closes suddenly during
deceleration.
The control unit receives a signal from the AC control
when the AC is tumed on oroff to enable it to adjust
the idle valve. Signals are alsosent
to thecontrol unit
from the
AC compressorso that the idle valve can be
adjusted each time the compressor turns on or off.
..
There is no signal to the control unit when the shuNer
switch is open. When driving, the control unit keeps
the idle valve partially open so that the negalive
pressure
in the intake manifold is reduced when the
gas pedal is released.
15

Design and function
Fuel system LH2.4 - 240
Igniti on system
contol unil
FUIII system
control unit
SYltem relay
iQ:::='J ~ Stl,-===
~~/ fJ
I)
Carbon
. fihM
System relay
Gove rn ed by the contr ol unit, it provides current to
the fuel pum p, the injector s, the cold start valve, the
air mass meter and to certain control unit functions.
The system relay and its functions are protected by a
20 amp fuse.
Fuses
The system relay is protected by a 25 amp fuse and
the tank pump
by a 15 amp fuse .
Evaporative Control System (EVAP)
This sy stem handles the gases that result Irom nor-
mal fu
el lankevaporation, keeping Ihem from escap-
ing and pollu1ing
th e air.
Via a hose system, the luel vapor passes from the
filler opening throu
gh a roll-over valve to a reservoir
("canister', "carb
on IIfter-). The fuel vapor is
absorbed here. n 1e reservoir is provided with an
EVAP valve wh ich prevents leakage of fuel vapor
while
the en gine is not in operaHo n.
®
Reservoir (carbon IIIter)
The
fu el vapors f ro m th e fuel tank enter the top of the
active ca
rb on filter and are absorbed. Air is pushed
out through a channel in the bottom of the filter.
Depending on tempera
tu re and otherconditio ns , the
filter can bind approx. 90 grams of fuel.
®
R oll-ove r valve
If the ve hicle leans sideways at more than a 45'
angle, this valve closes, helping to prevent fuel spills
during accidents.
@)
EVAP valve
This valve
is located at the top of the carbon filter and
is closed when the engine
is turned off. It 's also
closed during idling in order not
to interfere with the
automatic idle settings or make the fuel
mi xture too
rich. The
va lve is closed using vacuum pressure
taken Irom the intake manifold and through being
connected
to the throttle shutter po sitive terminal.
Increased engine load opens the EVAP valve,allow-
ing fuel vapor to flow from the carbon filter into the
engine intake manifo
ld . Air is drawn in at the same
time through the bottom channel. Under normal
conditions, the filter is empti
ed of fu el in 15 to 20
minutes.
16

Des ign and function
Fuel system LH2.4 - 240
®
Fuel system diagnostics
The fuel system has a built-in self-diagnostic system
and a funclions testing system_
It uses the same
diagnostic socket as the ignition system and Is lo-
cated behind the
Ie" spring strut tower in the engine
compartment.
The
di agnosticsystemusessocket2 fo rthe fuel sys-
tem and socket 6 for the ignition syste
m.
There are eighteen different fault codes in the diag-
nostic system.
It is capableof storing up to three fuel
system faults.
The fuel system control unit carries out continuous
checks of the following functions while the engine
is
running:
-The control unit's own internal functions.
-Lambda-sond and Lambda settings.
-Coolant temperature sensor.
-Air mass meter.
-Battery voltage.
-Throttle shutter.
-Ignition settings and engine rpm (through Ihe
ignition system control unit).
-Speedometer.
-Knock indicator.
-Idle speed air valve.
-Injectors.
Faults
in any of these funclions are registered in the
diagnostic system memory.
17

The Design and Function 01 the luel system has been
described on the preceding pages.
II is important to read
them
il you are to have a dear understanding 01 the next
section.
Fault tracing -Repairs -Maintenance
CONTENTS
Important! .........
Group 20 General .......
Page
. ....... _ . .. .......... 19
.
.... _....... ........ 21
Grou p 23 Fuel system
• Placement of components ......... .. .............. .. 22
• Fa ult tracIng ......... .. .... ...... ...... .. .. 24·31
Function
AI·A15
Complete overview 01 the luel system .
-Fuses, grounding connections, connectors .....32
·
Air leakage and throttle shutters ......................33-34
• Pumps, pre ss ure regulator, fuel lines ....... ....... 35 · 37
· Components, cabling. .. ............. .. ... 38·50
81 -
84
Cl·C6
Dl·D6
E l-E28
· Quick check of injectors ...
51
Fl
• Injectors, luel distribution pipe
and pressure regulator
.... ....... ...... .... ........ 52
18