check engine Citroen CX 1977 1.G Owner's Manual

Downloaded from www.Manualslib.com manuals search engine Op. MA.IE. 144-O 1 I - PRECAUTIONS TO BE TAKEN WHEN WORKII;(G ON A VEHICLE FITTED WITH THE (t L-JETRONIC n
SYSTEM.
1.
Do not run the engine if the battery leads are improperly secured
2. Do not use a quick-start charging trolley for starting the engine
3. Never disconnect the battery with the engine running
4. When charging the battery, disconnect the leads
5. Before checking the injection system, check the ignition : (advance, advance curve, proper grade of plugs 1
6. Remove the E C U before putting the vehicle through a paint-stoving oven
7. Check the conditions of the various connections
8. Never disconnect the E,C U. while the ignition is on
9. When checking compression, disconnect the positive terminal of the coil (in order to stop the injection signal). 10.
When carrying out a check requiring an ohmmeter, use exclusively a battery-powered ohmmeter. II. FAULT-FINDING.
1. THE ENGINE DOES NOT START, OR IS DIFFICULT TO START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P. 2
2. THE ENGINE STARTS, THEN STOPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P. 3
3. UNSTABLE OR INCORRECT IDLING SPEED, EXCESSIVE FUEL CONSUMPTION ........................ P:5
-4. ENGINE MISFIRES AT .ALL SPEEDS ........................................................................................................
P. 7
5. LACK OF POWER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................ P. 9

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 1. Energizing the system : ( DIAGRAM 1 )
_ Disconnect the E.C U
- Switch the ignition on
Using a voltmeter. ensure that each point in
dingrm 1 is effectively energised. after having tested the
earthing. If not, switch off the ignition. and test the circuit using a battery operated ohmmeter. With the
voltmeter connected between terminals ( 1 ) and ( 5) of the E. C.U., operate the starter the voltmeter must
register the ignition impulses If it does not. check the ignition
( ANNEXE A ).
2. Fuel pump feed ( on operating the starter ) ( DIAGRAM 2 )
- Disconnect the E C.U.
- Switch on the ignition
- On operating the starter. the fuel pump (
secureri rrt/rler the I c~hiclc’. uoor IIJO K. ti. ronr (, l~eol I must be
heard to operate by someone standing close by
If not switch off the ignition, and test the circuit using a battery operated ohmmeter.
The resistance between terminal (( 88 d H of the relay assembly ( c~r~tler 111~
L,H. honr/llor)~p ) and earth
must be 1 Q approx-
Make sure the petrol pump is properly earthed.

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.

Downloaded from www.Manualslib.com manuals search engine 5. Air-flow sensor ( DIAGRAM 5 )
- Disconnect the E.C.U.
- Using an ohmmeter check the continuity of circuits (( 6 )a, H 7 )) (( 8 H and (( 9 )) linking the air-flow sensor to
the multiple terminal board. as well as the continuity between each of the terminals
- The air-flow meter does not require any maintenance. It is not necessary to oil the flop. It must work without
high spot or catching
When the air-flow sensor is removed blank off the ducts so OS to protect it from dust
- Check the air circuit for air-tightness.
6. Resistors and injectors :
- A dirty injector may cause o lock of power. or on unstable idling speed.
- It is possible to test the functioning of the injectors with the engine idling by disconnecting each injector
in turn the engine rpm should decrease each time.
- Disconnect the E C U
- The resistance of an injector is 2 to 3 II.
- Each supplementary resistance is 5 to 7 R
- The volume delivered by an injector ( kept constantly open and under the normal operating pressure ) is
approximately 200 cm3 /min ( 12 25 cu in/min )-
- If the rubber pipe on one of the injectors appears wet on the outside, the injector must be replaced.
- Using an ohmmeter, check the continuity of the circuits

Downloaded from www.Manualslib.com manuals search engine 9. Cold-start injector, and thermal switch : ( DIAGRAM 9 )
- Disconnect the E.C.U.
- Remove the cold-start injector, and place it above a graduated container.
- Disconnect the thermal switch, and connect terminal (( 46 )) to earth
- Switch the ignition on and actuate the starter motor. the quantity delivered must be approximately
135 cm3 /min ( 8 l/4 cuin’min 1.
- Disconnect the injector: its resistance must be 4.2 Q at 20” C
- Connect the injector to the thermal switch.
- If the water temperature is below 35” C, on operating the starter motor, the cold-start injector must supply
petrol for the followinq amounts of time
- 7.5 sets for a temperature of (( - 20” C ))
-5 ” ” (( - 10“ c N
-3
” cc 0: c ))
-1 ” ” (( 20” c >)
- On operating the starter. terminal (( 4 )) of the E.C.U. terminal board must be enerqized ( voltmeter between
terminals (( 4 )) and 0 5 )) 1.
10. Switch on throttle butterfly spindle ( Idling speed function ) : ( DIAGRAM 10 )
- Disconnect the E.C.U
- Using an ohmmeter, check that there is no resistance between terminals N 2 H and (( 18 H of the multiple
connector, without touching the accelerator pedal.

Downloaded from www.Manualslib.com manuals search engine 11. Switch on throttle butterfly spindle ( maximum power function ) ( DIAGRAM 11 )
- Disconnect the E.C.U.
- Using a battery operated ohmmeter, check there is no resistance between terminals (( 3 H and (( 18 )) of the
multiple connector board, with the accelerator pedal fully depressed
t 12. E.C.U. : ( DIAGRAM 12) +
s
*
i :
2 - Visually check the condition of the terminals ( male connectors on the E-C U., and female connectors
on the multiple connector socket ).
- With the engine running, tap lightly on the E.C.U., to detect any possible defect in the soldering ( dry
joints ).

Downloaded from www.Manualslib.com manuals search engine OPERATION No MA.IE. 144-0 : (,hcrkir~g m/cl nrl;tts/ir/<~ I/W a I.-J~~/m,i~ ~~otectrot,ic Op. MA.IE. 144-O 25 fi~cl irijection systc~rti.
ANNEXE : A - CHECKING THE IGNITION
THE ENGINE TURNS, BUT DOES
NOT FIRE

Downloaded from www.Manualslib.com manuals search engine ANNEXE : B - CHECKING THE AIR CIRCUIT
L __- -’

Downloaded from www.Manualslib.com manuals search engine ANNEXE : C CHECKING THE FUEL CIRCUIT AND PRESSURE
- Remove the cold-start injector ( 1) and carefully
remove its petrol feed pipe.
- Connect pressure gauge ( 2) onto the cold-start
injector petrol line.
- Fit the cold-start injector zmto the manifold.
- Run the engine at idling speed the petrol pressure
must be regulated to 2 bars ( 29 psi ).
- Disconnect the vticuum pipe ( 3 i from the pressure
regulator the regulated pressure must be 2.5 bars
i 36 l/4 psi ).
If one of the readings is incorrect, check condition
of the flexible vacuum pipe for the pressure
regulator. as well as its aspect. If it is satisfactory
replace the pressure requlotor after making sure
that its VCICUU~ pipe is not blocked totally or
partially at the manifold end.
With the engine stopped, the pressure must
remain stable at 2 bars ( 23 psi ); if not, check
for a leak which could be found at the cold-start
injector, one of the main injectors. or at the level
of the pressure regulator valve diaphragm.