1988 CITROEN CX engine

GENERAL FEATURES
OF THE TRANSISTORISED IGNITION SYSTEM
TRANSISTORISED IGNITION
PRINCIPLE OF OPERATION
The plug spark is triggered by distributor (1) which comprises a coil located inside the field of a magnetic circuit
permanent magnet. The magnetic circuit has four fixed branches and four movable branches driven by the distribu-
tor shaft.
When the movable branches, in their rotation, come opposite the fixed ones, a variation of the magnetic field is
brought and current is induced into the sensor winding.
This current, in turn, triggers electronic module (2)
which builds up the current in ignition coil (3) primary winding
and then cuts it off, thus creating a high tension current in the coil secondary winding and triggering a spark from
the plug selected by the distributor rotor arm. IGNITION DISTRIBUTOR (I!
The advance curves are specific for each engine type
N: Distributor rpm
D = Vacuum Dl, in m.bars A:
Distributor degrees 02, in mm.hg
Pick-up coil resistance: 1100 Q sr 10% (990 to 1210 02)
Setting the distributor static timing on the engine is impossible owing to design.
A revolution of the distributor is required to create a variation of the magnetic field which will send a signal to the
module. Consequently, when fitting a distributor, place it in mid-slot; start the engine and adjust the distributor
by means of a timing light or a diagnosis console.
The duration and amplitude of the signal depend on the speed, therefore the DWELL ratio
is not significant.
The air gap between the branches is non-adjustable and it cannot be measured ELECTRONIC MODULE (2)
Intended to operate with the magnetically-triggered distributor.
Do not carry out a check with an ohmmeter since the results would not be significant.
Do not operate the module without cooling (aluminium plate heat sink and heat conductor grease).
The operation of the ignition system is possible with the engine stopped: - connect an earthed sparking plug to
the coil HT lead; short ” + 12 volts” pulses on module red lead (path 5) (with all leads connected, cap lifted) will
generate a spark from the plug: simulation of a signal from the distributor pick up).
Do not operate the module and coil without a plug and HT lead, (It could result in the module being destroyed). IGNITION COIL (3)
The coil must not be kept alive under 12 volts without its module (overheating).
The coil current flow is generated by the module which then reduces it, prior to cutting it off when the engine
ignition timing occurs.
Only use a rev. counter with a UT induction clip.

CHECKlNG THE TRANSISTORISED IGNITION
ELECTRO-MAGNETICALLY TRIGGERED TRANSISTORISED IGNITION
PRELIMINARY CHECKS:
Inspect:
- the connection of the different leads (in particular to coil: a bad connection can cause a high voltage drop preven-
ting the current from passing into the coil primary winding (I 5 A approx),
- condition of the leads : (circuits broken, short-circuits across screening, etc.),
- condition of the sparking plugs (deposits, cracks due to overtightening),
- condition of the distributor cap (wear, cracks) and the rotor arm (loose).
Disconnect the interference suppression capacitor and the diagnosis harness, from the circuit.
Carry out a ((spark test)) with the starter motor and one plug earthed.
IMPORTANT: The module may be destroyed if one of the secondary wires is too far from the earth. CHECKING THE COIL (3) (ignition module and supply to coil disconnected):
MEASUREMENT OF Ohmmeter placed between channels No. Reading (in 0)
Primary winding resistance 1 and 4 DUCELLIER 0.76 to 0.84
BOSCH 0.74 to 0.90
Secondary coil resistance 1 4 and HT coil contact DUCELLIER 5700 to 6300
or
BOSCH 7425 to 9075
Insulation 1 or 4 and earth 00
Checking the coil power supply using a lamp or a voltmeter:
- Switch on the ignition: there should be a 12V current between the “BAT” terminal of the coil and the earth
- Switch off ignition. CHECKING THE IGNITION MODULE (2):
The module is designed to function with the ignition distributor and the coil.
- Do not operate the module without cooling (aluminium plate heat sink) or ventilation
- Do not check the module with an ohmmeter since the results will be non-significant.
Checking the module power supply using a lamp or a voltmeter:
- Disconnect the module connector
- Switch on the ignition: there should be a 12 V current between the channel 4 of the connector and the earth.
- Switch off ignition.
The low voltage ignition circuit being connected (in working order), disconnect the coil - distributor HT lead on
the distributor side and connect it up to an earthed plug: by sending short pulses ( + 12 VI to channel 5 (red wire)
from the module, sparks should occur at the plug (simulation of distributor spark current). CHECKING THE IGNITION DISTRIBUTOR (1):
Test the impulse generator with the module connector disconnected. MEASUREMENT OF:
Resistance
Earth
Insulation Ohmmeter placed between channels No. 5 and 6
2 and engine earth
5 and 2 then 5 and 3 Readings (in Q) 950 to 1250 approx.
0
m
,

CHECKING THE TRANSISTORISED IGNITION MA
210.0/l 7 CHECKING THE DISTRIBUTOR ON TEST BENCH, Fig. I
To check the magnetic distributor on the bench, a transistorised module in good condition is essential. Use the
vehicle module and leads if the bench is not equipped. The ignition coil is not required.
CHECKING THE CENTRIFUGAL SPARK ADVANCE
Fit the distributor onto the bench:
Connect module (3) and distributor (I 1 to the harness (2)
Connect wiring harness plugs (2) to test bench:
To check the distributor: Fig. II and Ill.
Compare the distributor centrifugal spark advance curve with the theoretical curve:
- If the curve plotted does not correspond to the theoretical curve, modify the spring tension by bending the spring
hooking point support plate.
In order to do this, remove the cap and alter the spring tension by bending the attaching bracket, Fig. Ill and IV.
(D
: release the spring, T : tighten the spring) , Curve measured
I
II
Ill
IV Spring concerned
5
5
4 released
4 not in use Bending direction
T
D
T
D
CHECKING THE VACUUM SPARK ADVANCE
Compare the distributor vacuum spark advance curve with the theoretical curve
NOTE: The vacuum spark advance device is not adjustable: If the curve measured is out of tolerance, change the
capsule. ADJUSTMENT ON THE VEHICLE
Distributor timing:
- Fit the distributor, positioning it approximately midway between the slotted holes.
- Start the engine.
- The vacuum capsule being disconnected, use a strobe lamp to set the distributor timing to:
Advance (degrees
before TDC)
Engine rpm cx20 cx22
IO0 lo0
750
I 800
- Reconnect the vacuum capsule.
8531

CHECKING THE INTEGRATED ELECTRONlC
IGNITION (I.E.I.)
TEST PROCEDURE USING CONVENTIONAL EQUIPMENT
on the CX 2500 vehicle with M 25/659 type engine
l Checking the voltage in the secondary winding of each coil
0 Operating procedure: Disconnect one sparking plug and bring the end of the released wire 1 cm approx
from the crankcase. (Repeat the operation for each set of cylinders).
l Operate the starter motor:
if a spark occurs The incident is not to be attributed to the I.E.I.
Check the injection system, the valve timing, the rockers etc.
- examine the engine sparking plugs.
- inspect the circuit between the I.E.I. control unit white terminal 1 and the fuel
injection control unit terminal 15 for continuity: read 0 0, the connectors from
the control units being disconnected.
if no spark occurs The incident is due to the ignition system--ccarry on to next tests.
l Working on the primary winding of each coil
Operating procedure: Connect a 12V warning lamp of the Wedge base type between the negative and
0 the positive terminals of the coil (i.e. between terminals 1 and 3, connectors con-
netted to coil).
l Operate the starter motor:
if no regular breaks occur incident in the coil primary winding
or
incident in the E.C.U. control circuit.
if regular breaks occur incident in the secondary winding
The following checks are to be carried out with I.E.I. and fuel injection control units connectors disconnected.
l Checking the coil primary windings:
Operating procedure: Measure the resistance between terminals 1 and 9 of the I.E.I. control unit black
0 connector: Read = 2.5 0.
Warning: the ignition should be switched off.
If the reading is incorrect, investigate for a failure in this circuit.
l Checking the E.C.U. pick up sensors:
co Operating procedure: Measure the resistance between terminals 5 and 12 then 6 and 13 of the I.E.I.
control unit black connector: Read = 50 a.
l Checking the feed for the E.C.U. and earth connection, with ignition switched on
Operating procedure: Measure the voltage between terminals IO (white connector) and 2 (black con-
nector) of the I.E.I. computer: Read the battery voltage.
The same check should be carried out between terminals 2 (earth) and 11 of the black connector:
ignition switched on, starter motor operated, read the voltage.
69 l Check that the distance between the datum sensor and the flywheel ring is 1 mm + 0.5.
0 l Incident on the ignition circuit secondary winding: make sure that the resistance of each coil
winding is: 350014000 a.
8531

CHECKING THE I.E.I.
TEST PROCEDURE USING CONVENTIONAL EQUIPMENT
on the CX 2500 Turbo vehicle with M 25/662 type engine
0 Checking the voltage in the secondary winding of each coil
0 Operating procedure: Disconnect one sparking plug and bring the end of the released wire 1 cm approx
from the crankcase. (Repeat the operation for each set of cylinders).
0 Operate the starter motor,
if a spark occurs
if no spark occurs The incident is not to be attributed to the I.E.I.
Check the injection system, the valve timing, the rockers etc.
- examine the engine sparking plugs.
- inspect the circuit between the I.E.I. control unit white terminal 1 and the fuel
injection control unit terminal 15 for continuity: read 0 Q, the connectors from
the control units being disconnected.
The incident is due to the ignition system-carry on to next tests.
l Working on the primary winding of each coil
Operating procedure: Connect a 12V warning lamp of the Wedge base type between the negative and
the positive terminals of the coil (i.e. between terminals 1 and 3, connectors con-
netted to coil).
l Operate the starter motor,
if no regular breaks occur incident in the coil primary winding
or
incident in the E.C.U. control circuit.
if regular breaks occur incident in the secondary winding
The following checks are to be carried out with I.E.I. and fuel injection control units connectors disconnected.
0 Checking the coil primary windings:
Operating procedure: Measure the resistance between terminals 1 and 9 of the I.E.I. control unit black
0 connector: Read = 2.5 Q.
Warning: the ignition should be switched off.
If the reading is incorrect, investigate for a failure in this circuit.
l Checking the E.C.U. pick up sensors:
OI Operating procedure: Measure the resistance between terminals 5 and 12 then 6 and 13 of the I.E.I.
4
control unit black connector: Read 2: 5OQ
0 Checking the feed for the E.C.U. and earth connection, with ignition switched on.
d 5 Operating procedure: Measure the voltage between terminals 10 (white connector) and 2 (black con-
nectar) of the I.E.I. computer: Read the battery voltage.
The same check should be carried out between terminals 2 (earth) and 11 of the black connector:
ignition switched on, starter motor operated, read the voltage.
@ 0 Check that the distance between the datum sensor and the flywheel ring is 1 mm + 0.5.
0 * Incident on the ignition circuit secondary winding: make sure that the resistance of each coil
winding is: 350014OOOQ.

CHECKING THE IGNITION SYSTEM
USING CHECKING EQUIPMENT OUT 106 029T
The instrument can be utilised on CX 2400 I.E. with naturally aspirated engine and CX 2500 I.E. TURBO. Howe-
ver, on CX 2400 I.E. having an integrated electronic ignition system with a single connector E.C.U., it is neces-
sary to proceed as follows:
- connect the I.E.I. control unit to the black connector of OUT 105 029.T
- set the switch of the apparatus to the “1 connector” position
- I.E.I. with 1 or 2 sensors can be checked with this device.
a) Testing the ignition coil primary winding:
- The warning lamps, one at each coil, blink rythmically with the impulses transmitted to their primary win-
ding. Steady blinks indicate that there is enough current to generate a spark in the secondary winding.
- The switch situated under the warning lamps makes it possible for the primary windings of both coils to
be insulated, by pushing, in the “out of circuit“ position, any interference coming from the HT circuit when
the frequency of illumination for sensor warning lamps is checked.
- If the warning lamps blinking is correct, the failure may be caused by:
- the ignition information to the fuel injection control unit, (paragraph c),
- the secondary winding (coil wires, coils),
- any other item required for a correct operation of the engine such as injection, valve gear, rockers etc.) -
If the warning lamps blinking is not correct, examine the control unit warning lamps, (paragraph b),
b) Testing the sensors: -
The warning lamp connected with the “datum” sensor blinks rythmically with the impulses transmitted by
the peg, i.e. one blink per engine revolution, (2 sensors fitted).
- The warning lamp connected with the “flywheel pick up” sensor, blinks rythmically with the impulses sent ’
by the flywheel teeth.
The frequency of the flashes is such as they can hardly be seen.
Apparently, the lamp stays on, (1 or 2 sensors fitted).
On the CX 2400 I.E. and 2500 I.E. with normally aspirated engine, the vacuum pressure warning lamp lights
up momentarily after a sharp acceleration: this warning lamp is no longer usable on the CX 2500 I.E. with
turbocharger.
c) Tests related with the I.E.I. control unit:
E.C.U. functions: -
The rev. counter warning lamp blinks rythmically with the impulses transmitted to the rev. counter.
- The injection warning lamp blinks rythmically with the impulses sent to the fuel injection control unit
+k 8531

CHECKING THE IGNlTlON ADVANCE
of the I.E.I. system
On CX vehicles fitted with I.E.I.
These vehicles having fixed sensors, are not equipped with TDC sensors
I) Marking the TDC:
Draw a mark on the crankcase, in the opening located next to the flywheel pick up sensor
- Remove the 1st or 4th cylinder sparking plug
- Finding the T.D.C. with a locating peg: jack up the vehicle on one side and engage a gear.
Rotate the road wheel in one direction.
Mark down the place where locating pin will enter the flywheel.
Draw a temporary line on the flywheel ring. Rotate the lifted road wheel in the opposite direction, with
the pin still engaged. Mark the position of the pin in the flywheel ring. Take an average of these two marks-
which corresponds to the TDC. Draw a white paint mark on the flywheel ring, opposite the one on the
crankcase.
- Refit the sparking plug.
2) Testing the development of the speedometer advance curve:
- Connect a phase shifting strobe lamp
- Set the strobe lamp to the 2 cyl. u stroke or 1 cyl. 2 stroke position.
- Disconnect the pipe of the load correction depression operated capsule from the inlet manifold. Blank
off the orifice.
- Run the engine and check the advance curve development.
3) Testing the operation of the air-operated capsule on normally aspirated engines:
- Blank off the vacuum capsule venting orifice.
- Connect a vacuum pump to the capsule pipe.
- Run the engine to 2.000 rpm; record the advance reading.
- Create a 400 mbar depression in the vacuum capsule.
The ignition advance increases by about 15’ and the engine accelerates to 200 rpm approx.
On turbocharged engines:
- Connect a vacuum-pressure pump to the capsule pipe.
- Rotate the engine to 200 rpm. Read the advance.
- Build up a 500 mbar depression in the capsule:
- There will be a 22” increase of the ignition advance, approx. and about a 500 rpm engine acceleration.
- Build up a 500 mbar pressure in the capsule:
- There will be a -1 1 o decrease of the ignition advance, approx. and about a 500 rpm engine slowing down
- Pinking: occurs when the engine speed exceeds 1.000 rpm. The warning lamp should light up in the
following cases:
- anti-knock sensor system broken or short-circuited,
- knock sensor broken or short circuited,
- improper earthing provided by the knock sensor.
- Check the operation with the strobe lamp, and a 2.000 rpm engine speed Record the ignition timing.
- Disconnect the knock sensor:
The ignition advance decreases by IO’ approx.

REPAIR OF THE HYDRAULIC SYSTEM
FITTING PRECAUTIONS
PRECAUTIONS TO BE TAKEN WHEN WORKING ON
THE HYDRAULIC UNITS OR THE SYSTEM
The correct functioning of the entire system presupposes perfect cleanliness of the fluid and the hydraulic
units. Stringent precaut!ons must therefore be taken when working on the hydraulic system and during the
storage of the fluid and components. 1. HYDRAULIC FLUID:
Mineral hydraulic fluid (LHM) is the only suitable type and must be used to the exclusion of all others in the hydrau-
lic system of the car.
This LHM fluid is green in co/our and similar to engine oil.
The use of any other would ruin the rubber rings and seals in the system. 2. RUBBER UNITS AND PARTS:
Suitable components are identified by their green co/our and may only be replaced by genuine replacement
components painted or marked in green.
All rubber components (seals, hoses, diaphragm, etc...) are of a special quality for use with LHM fluid and are
identified by their white or green colour. 3. STORAGE:
Components must be stored, full of fluid and blanked off. Like the piping, they must be protected against shock
and the ingress of dust.
Rubber tubing and joints must be stored away from dust, air, light and heat.
LHM hydraulic fluid must be stored in its original containers carefully sealed. We advise the use of one litre (for
topping up) or five litre cans (for refilling) to avoid having to keep opened containers. 4. CHECKS BEFORE CARRYING OUT WORK:
Before-working on the hydraulic system in case of faulty operation, ensure the following:
a) That the controls or the mechanical linkages of the units or the group of hydraulic units involved are
not stiff in operation
I I
b) and that the HP circuit is under pressure, as follows:
With the engine at idling speed:
- Unscrew the pressure-release screw on the pressure regulator by one turn to one turn and a half: a sound
of leakage should be heard from the regulator.
- Retighten the release screw: cut-out must occur which results in a reduction in the running noise emitted
by the H.P. pump.
If not, check in the following sequence:
- that there is sufficient fluid in the reservoir,
- that the reservoir filter is clean and in good condition,
- that the H.P. pump is primed and there is no air leak on the suction side of the pump,
- that the release screw of the pressure regulator is correctly tightened,
- that sealing ball (2) is in position, (see Fig. I and II, page 5).