sensor Citroen CX 1981 1.G Workshop Manual

Downloaded from www.Manualslib.com manuals search engine I. CHARACTERISTICS
:
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5 Cooling system : Water cooled.
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T cx 2000 cx 2200 CX 2400 and Prestige
CX 2400 GTI
- Type ( on engine p’late ) : _..._................... M 20/616 M 22/617 M 23/ 623
M 23/622
Cubic capacity : . . .._......_...............
1985 cc 2175 cc 2350 cc 2350 cc
Transversely mounted, inclined
300 towards the front
Number of cylinders : _........................... 4 (iI/ linr, J 4 Iin linr,)
4 (irr /iUP J 4 f in lin i’ ,
Bore : 86 mm 90 mm 93.5 mm 93.5 mm
- Stroke : .,.,,_,.,.,....____.,.. .._._.....................
85.5 mm 85.5 mm 85.5 mm
85.5 mm
Compression ratio :
9/I 9/l 8.7511 8.7511
Maximum power ( DIN ) : . . . .._................... 102 bhp at 5500 rpm 112 bhp at 5500 rpm 115 bhp ot 5500 rpm
128 bhp at 4800 rpm
Maximum torque (DIN)
: . . 15.5 m.kg (112 ft.Ib ) 17 m.kq (123 ft.Ib) 18.2 m.kg ( 132 ft.Ib)
20.1 mkq (145 ft.Ib)
at 3000 rpm at 3500 rpm at 3000 rpm
at 3600 rpm
Maximum engine rpm in 4th gear :
* 13/62 final drive rtrtio :
5600 rpm 5800 rpm 5900 rpm
*14/61 final drive ratio ( -1 1’175 J 4600 rpm
Maximum engine rpm in 5th gear
(
13,‘62 final drive ratio ) : ,._............,..,........,....,.,........,..,.,..... .._.........,................ .._..._...................
5600 rpm
* NOTE : For CX 2200 and CX 2400 vehicles fitted with a torque converter, the maximum rpm in 3rd gear is 5600 rpm.
: Lubrification :
i
Under pressure, supplied by o gear-type oil-pump driven by the camshaft.
2
External oil filter cartridge ( PURFLUX, LS 105 type ).
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i Fuel supply :
a
i a) Engines fitted u~ifh a rnrbuwffor
WEBER compound-type twin choke carburettor (s.ee Operations MA. 142-00, 142-00 a, 142-00 b far the type, and the identification marks )
Dry-type air filter, with filter cartridge.
Mechanical fuel pump, driven by on eccentric on the camshaft.
b) i?ugi,jes ji/f.rd II ith /LIP/ iniPr/ioo :
BOSCH L-Jetronic electronic fuel injection system
Grade of pet,ol to be used : > ._,,,,.,_.._,,,,,.,......... . .._...o....._............................................. K.
99 Orrani ralrrig (FRANCE : Super grade ) (U.K. : 4-star )
Ignition :
Distributor ( DUCELLIER or MARELLI ) driven by the camshaft.
NOTE : The M 23/622 engine with fuel injection is fitted with (I DUCELLIER distributor with a magnetic sensor, and an u AC-DELCO /a electronic module.
- Spark pluqs : .................................................................................................................................... shorf warh
Firing o&r : .................................................................................................................................... 1 - 3 - 4 - 2 f tbu cylinders ale INR&Cd 011 the roc6w COI rr,
Timing :
Side mounted camshaft located in crankcase.

Downloaded from www.Manualslib.com manuals search engine 2
OPERATION No MA.IE. 144-00 : Chtiractcristics o/ the e 1,-Jc,tror,ic H clcctroltic
fire1 injc ctiwt systettt.
((L-JETRONIC,,
The H L-Jetronic 1) system is’an intermittent low-pressure injection system which injects petrol into the inlet
manifold.
The system measures the quantity of air drawn in by the engine. which is the main parameter for calculating
the amount of fuel. to be injected. The metering of the fuel is carried out by electro-magnetically triggered
injectors. These are under constant fuel pressure. The quantity of fuel injected is proportional to the duration
of injection. which in turn is optimally determined for any given engin& operating condition by an electronic
control unit ( E.C.U. ) from information supplied by several electric sensors.
One of the principal contributions of the H L-Jetronic H system is the reduction in the level of pollution of the
exhaust emissions.
The (( L-Jetronic v system is made up of the following components :
1
: Electric fuel pump
2 : Fuel filter
3 : Thermal switch
4 :, Double relay
5 : Electronic control unit ( E.C.U. )
6 : Supplementary air control
7 : Pressure regulator
8 : Injectors
9 : Cold-start injector
10. Idling speed adjustment screw
11 : Air-flow sensor ( with incorporated air temperature sensor )
12 : Switch on throttle butterfly spindle
13 : Additional resistors for the injectors (8)

Downloaded from www.Manualslib.com manuals search engine OPERATION No MA.IE. 144-00 : Chu~acte~istics of the (( L-Jetronic n electronic
fuel injectiari system Op. MA.IE. 144-00 5
-AIR INLET SYSTEM’
Air drawn in via air filter ( 1 ) passes through the air-flow sensor (2’), via butterfly ( 3) and arrives in the inlet
distribution chamber, each pipe of which (4) leads to a cylinder.
-
‘I
Each cylinder has an electro-magnetic injector which is located very close to the inlet valve in order to improve
engine performance.
The supplementary air control (6) is located in parallel with the butterfly, and supplies the supplementary air
required by the engine to run smoothly when cold.
_ Once the engine has reached its normal running temperature, the idling speed air-flow is provided by a by-pass
valve
$ ( 5) which by-passes the butterfly as well.
.
2
co
T
$ It is important that the system be air-tight downstream from the air-flow sensor, so that no (( secondary )) air can
I
2 be drawn in, which would falsify the air-volume reading.

Downloaded from www.Manualslib.com manuals search engine OPEdATlON N- MA.IE. 144-00 : C1 3aractcJristics o/ the e L-Jetro~ic n elcctrorlir Op. MA.IE. 144-00 9
fuel injectian systwn. E.C.U; ( ELECTRONIC CONTROL UNIT )
Apart from three integrated circuits ( I.C. ) forming the main part of the E.C.U., there are in addition only a few
semi-conducting components condensers, calibrating resistors and filters so as to avoid.any interference.
I
The function of the E.C.U. is ,to supply an impulse to the injectors, and to control their opening for a precisely
defined amount of time. The E.C.U. to this effect uses the information provided by all the engine sensors which
translate the operating conditions of the engine into electric impulses.
All the injectors are connected in parallel, and inject fuel simultaneously twice for each rotation of the camshaft
( therefore,twice for each engine cycle ), injecting half the quantity of fuel required each time With this system
it is not necessary for the camshaft angle to coincide with the beginning of injection point, which eliminates the
need for a generating switch incorporated in the distributor.
The injection impulse control is ensured by the distributor impulses. The distributor produces four impulses for
every operational cycle. Since injection only occurs twice in every cycle, the E.C.U. must divide the frequency
by 2.
The impulses coming from the distriLti, are transformated into square waves by the waveform shaper. Since
injection only occurs twice for each camshaft rotation, whereas the distributor provides 4 impulses in the same
amount of time, the frequency of the impulses must be divided by 2 in the frequency divider.
These signals are used to charge a condenser. The condenser discharge determines the beginning of injection
point; the position of the air-flow sensor flap ( which determines the quantity of air drawn in ) being the main
parameter for calculating the duration of injection.
At the multiplying stage of the E.C.U., various correction values ( full load and idling speed via throttle butterfly
spindle switch, engine temperature via the water temperature sensor, air temperature via the air-temperature sensor
located in the air-flow sensor ) are combined with the signals from the air-flow sensor and the injt,ztion frequency
in order to determine the injection duration which is transmitted to the injectors by way of impulses.
The time it takes for the injector needle to open and close depends on the battery voltage.
As the supply voltage increases, the injection duration increases.
The fact that the quantity of fuel injected depends
on the voltage is cancelled out by the fact that the injection duration is inversely proportional to the voltaqq,in the
E.C.U.
The final impulse determines the time during which the injectors are connected to earth ( injection duration ‘supplied
by the output stage ).

Downloaded from www.Manualslib.com manuals search engine 10 OPERATION No MA.IE. 144-00 : Characteristics o/ the K L=Jetronic )) electronic
/uel iujectian system. AIR-FLOW SENSOR ( 1) :
The role of the air-flow sensor is to supply the E.C.U. with a signal proportional in voltage to the quantity of air
drawn in.
With the engine running, the sensor flap is maintained at an angular position determined by the intensity of the-air- ,
flow, against the resistive action of a spiral spring. The resistance to deflection of the sensor flap, produced by the
spiral spring, is calculated so as to compensate for any mechanical friction ( bearings, bushes ) and to limit the
pressure drop at the flap.
The movement of the sensor flap is damped by a blade rigidly attached to it. This damping blade rotates inside a
housing in which it is a close fit. The operating clearance determines the degree of damping. The use of a damping
blade cancels the effects on the angular position of the sensor flap of pressure variation’s in the inlet collector.
A potentiometer, actuated by the sensor flap spindle, transforms movement of the sensor flap into an electrical circuit which is transtiitted to the E.C.U.. The voltage of the electrical ‘current is inversely proportional to the
amount of air drawn-in.
In order to cancel the effects of any combustion taking place in the inlet manifold, a one-way valve is incorporated in the sensor flap.
Thanks to a by-pass channel, a small quantity of the air drawn ,in by-passes the sensor flap. This offers the possibility
of determining the air/lfuel mixture at idling speed by’varying the diameter of the by-pass channel, since the air going
through the by-pass is not measured. The switch for the pump ( engine running ) and the air temperature sensor are
located in the air-flow sensor.

Downloaded from www.Manualslib.com manuals search engine OPERATION No MA.IE. 14400 : @ nracteristics of the I( L-~elronic x cl~~tronic
fuel injrction sysfem. Op. MA.IE. 14400 11
AIR-FLOW SENSOR
‘otentiometer ~~uuuuLluu~

Downloaded from www.Manualslib.com manuals search engine INJECTORS ( i ) :
Each cylinder is supplied by an electro-magnetically controlled injector which is fitted in the inlet duct;
the injector vaporises the fuel upstream of the inlet valve. In the case of the (( L-Jetronic )) system. all the
injectors operate simultaneously. However, in order to ensure regular fuel supply to the cylinders, there are
two injections for each rotation of the camshaft, each one supplying half the metered quantity of fuel required I
for the complete engine cycle.
The injector consists of a valve housing and an injector needle fitted with a magnetic core. The mobile magnetic
/
core is in one piece with the needle which in turn is compressed against the air-tight injector housing seat by
a helicoidal spring. At the rear end of the injector, there is a solenoid. and at the front a guide for the injector
needle.
Impulses coming from the E.C.U. create a magnetic.field in the solenoid; the magnetic core is attracted, and the
needle lifts off its seat the fuel under pressure is free to pass through, The movement of the magnetic core is
approximately 0.15 mm.
The duration of opening is determined by the E.C.U. as a function of the operating conditions of the engine at the
moment in question{. TEMPERATURE SENSORS t(
When the engine is started, for a temperature of approximately - 20” C, it needs two to three times more fuel than
when it has reached normal operating temperature. The enrichment of the mixture must be reduced as the engine
warms up, and must cease as soon as the engine has reached normal operating temperature. In’order to start off
this regulating procedure, the engine temperature must be communicated to the E.C.U. ( Electronic Control Unit ).
This is the object .of the temperature sensors.
The temperature sensor consists of a hollow threaded rod in which is located an NTC Thermistor made in semi-
conducting material. The letters .NTC, which signify (( negative temperature coefficient )) characterise its specific
property : its electrical resistance decreases as the temperature increases.
The (( L-Jetronic 1) system is fitted with.a water temperature sensor ( 2) and an air temperature sensor, the latter
situated in the air-flow sensor.

Downloaded from www.Manualslib.com manuals search engine ELECTRIC PETROL PUMP
The petrol pump is of the multi roller-vane type, driven by an electric motor which is energized as long as the
ignition is switched on. The rotor, which is fitted eccentrically in the pump housing, has metal roller vanes in
grooves around t.he periphery which, when they are forced outwards under the action of the centrifugal force, ensure
the system-is sealed.
Fuel is drawn into the cavities which,appear in between the roller-vanes, and is then forced into the injection
piping.
The electric motor is submerged’ in fuel. However, there .is no fire risk, since there is never any combustible
mixture in the pump housing. The pump supplies more fuel than the engine consumes under full load, so that
there is always sufficient pressure in the fuel system, whatever the engine speed. Excess fuel flows back to
the tank.
Once the ignition is on, the pump operates at the same time as the starter motor. Once the engine is running, the
airflow sensor energizes the pump.
Thanks to this type of.system, if an injector is faulty ( leaks ) the cylinder in question cannot be flooded if one
has ommitted to switch the ignition off. PETROL FILTER (1) :
A fuel filter, fitted between the pump and the injectors, prevents any impurities from reaching the injectors. PETROL PRESSURE REGULATOR ( 2 ) :
The fuel pressure is maintained constant by the pressure regulator. It comprises a metal housing
is a diaphragm., One side of the dipphragm.is subjected to the fuel under pressure, and the other 2
to the action of a calibrated spring. inside which
side is subjected
When the fuel pressure is in excess of 2 bars ( 29 psi ), the diaphragm lifts and allows fuel to flow back to the
tank.
The pressure provided by the regulator is pre-adjusted at the factory. The chamber on the side of the spring is
connected via a flexible pipe to the inlet manifold. Therefore, the difference between the pressure in the inlet
manifold and that of the fuel is maintained constant.
For any engine load, the drop in pressure at the injectors is therefore the same.

Downloaded from www.Manualslib.com manuals search engine Ill. CHECKING AND ADJUSTING
1
. Energizing the system ..................................................................................................................
2. ,Fuel pump feed ( on operating the starter ) .............................................................................
3. Fuel pump feed ( with engine running ) ...................................................................................
4. Supplementary air control ...........................................................................................................
5. Air-flow sensor ............................................................................................................................
6. Resistors and injectors ................................................................................................... . ........
7. Water temperature sensor ............................................................................................................ .
Dingram 7
8. Air temperature sensor ...............................................................................................................
9. Cold-start injector, and thermal switch ...................................................................................
10. Switch on throttle butterfly spindle ( idling speed function ) ............................................ 11
Switch on throttle butterfly spindle ( maximum power function ) ...................................... 12.
E.C.U: ......................................................................... ..~ ............................................................... . . Diagram 1 I ANNEXE : A
: Checking the ignition .................................................................................. Page 25 B
: Checking the air circuit ................................................................................ Page 26
C : Checking the fuel system and the fuel pressure ........................................... Page 27 D
: Adjusting the idling speed and the exhaust emission .............................. Page 28 NOTE
: On the wiring harness for the injectors, the numbers of the terminals on the E.C.U. terminal board are
visible on the rear section. after having withdrawn the casing secured by the end screw.

Downloaded from www.Manualslib.com manuals search engine Op. MA.IE 444-O 15
3. Fuel pump feed ( with engine running ) : ( DIAGRAM 3 )
- Disconnect the E.C.U.
- Disconnect from the air-flow sensor the air hose to the butterfly housing
- Switch on the ignition:
- Actuate the air-flow sensor flap by hand’ when the petrol pump contact closes the pump should be heard
working.
If not, test the circuit using a
battery operated ohmmeter, without forgetting to test between terminal G 36 ))
on the air-flow sensor and terminal H 20 .)) on the E.C.U. for continuity ( The 2nd terminal is not connected
to the E.C.U. ).
- The resistance between terminals (( 86 b H and G 85 )) on the relay box f //j/nor thc~ I~./I. h<~ntllnr~tp ) must be
between 52 and 78 12.
P 4. Supplementary air control ( DIAGRAM 4 )
4
c
5
6
- Disconnect the E.C.U.
-E
? - Check that the supplementary air control is properly connected ( arrow on the casing )~
In
If it is fitted the wrong way round. the port may be blocked.
- The resistance between terminals (( 34 1, and (( 48 )) on the- supplementary air control must be 50 Q approx-
- Visual checking the port on the supplementary air control must be open when the engine is cold, and closed
when the engine temperature is above 60” C
- With the engine cold. if the air pipe to the supplementary air control is flattened the engine rpm must decrease.
With the engine warm, if the air pipe is disconnected, the engine must accelerate.