1995 RENAULT MEGANE SCENIC sensor

INJECTION
Location of components
17
F3R engine
17Oxygen sensor
(tightening torque: 4.5 daN.m)
99224R
17-16

INJECTION
Special notes on sequential injection
17
F3R engine
PRESENTATION
The F3R engine is fitted with sequential injection.
Injection of fuel is not carried out simultaneously
to all four cylinders as with conventional injection,
but cylinder after cylinder when they are at the
start of the inlet phase.
To do this, it is necessary for:
- each injector to be connected separately to
the computer (injector n° 1 is at the flywheel
end),
- the computer to know which cylinder is at the
inlet phase.
To determine the cylinder at the inlet phase, the
computer uses 2 sensors:
- the TDC sensor,
- the cylinder reference sensor.
The TDC sensor allows the computer to determine
the engine speed, and to know which cylinders
are at TDC:
- cylinders 1 and 4 at TDC,
- cylinders 2 and 3 at TDC.
The cylinder reference sensor allows the computer
to know which of the two cylinders at TDC is at
the start of the inlet phase.
DEFECT MODE IN THE CASE OF A FAULT WITH THE
CYLINDER REFERENCE SENSOR
The system remains in sequential injection. The
cycle 1 - 3 - 4 - 2 is retained.
When fuel is injected for the first time, or at the
beginning of the starting phase, the computer
decides arbitrarily to inject fuel to cylinder n° 1
when cylinders 1 and 4 are at TDC.
Two possibilities may then arise:
- the system is phased correctly,
- the system is out of phase by one revolution.
Operation of the engine is not greatly affected.
DESCRIPTION
The cylinder reference sensor (A) is located at the
end of the camshaft. It is mounted by three bolts
on to the cylinder head.
The sensor is opposite a long target of 180°. This is
mounted on the end of the camshaft.
If the target is located within the sensor air gap,
12 V is sent to the computer.
If the target is not in the sensor airgap, 0 V is sent
to the computer.
SENSOR OPERATING PRINCIPLE
The sensor is supplied with 12 Volts. The computer
sends it a 5 V feed on track 2.
Depending on the position of the target, the sen-
sor closes the circuit and earths this voltage (the
computer receives 0 V), or the sensor leaves the
circuit open (the computer receives 12 V).
99238R3
17-19

INJECTION
Special notes on sequential injection
17
F3R engine
PRINCIPLE FOR RECOGNISING THE CYLINDER AT THE INLET PHASE
Depending on the signal from the TDC sensor, the computer knows at what moment cylinders 1 and 4 are at
TDC and at what moment cylinders 2 and 3 are at TDC. (For further explanations refer to section 17
"Ignition").
Cylinders 1 and 4 are at TDC,
- if the signal from the cylinder reference sensor is 0 Volts, cylinder 4 is at the start of the inlet phase,
- if the signal from the cylinder reference sensor is 12 Volt, cylinder 1 is at the start of the inlet phase.
Cylinders 2 and 3 are at TDC,
- if the signal from the cylinder reference sensor is 0 Volts, cylinder 3 is at the start of the inlet phase,
- if the signal from the cylinder reference sensor is 12 Volt, cylinder 2 is at the start of the inlet phase.
LOGIC
Signal from cylinder
reference sensorCylinder at start of inlet phase
12 Volt 1
0 Volts 4
12 Volt 2
0 Volts 3Cylinder at TDC
1 - 4
2 - 3
17-20

INJECTION
Special notes on sequential injection
17
F3R engine
A 1 rotation of the crankshaft
B 1 rotation of the camshaft
C TDC 1 - 4
D TDC 2 - 3
1 Cylinder 1 at inlet
2 Cylinder 2 at inlet
3 Cylinder 3 at inlet
4 Cylinder 4 at inlet
5 Gap in flywheel
684° or 14 teeth
7 30 teeth
X Flywheel target
Y Camshaft target
Z Voltage from cylinder reference sensor
NOTE : All values are given in TDC degrees.
98406R1
17-21

INJECTION
Special notes on sequential injection
17
F3R engine
1.REMOVING THE CYLINDER REFERENCE
SENSOR
Disconnect the sensor
Remove:
- the cylinder reference sensor (A) (one bolt),
- the cover (B) (three bolts).
Target (C) is secured on the end of the camshaft
by a spring ring.
To release the target from the camshaft:
• Rest a copper hammer behind the target.
• Use a mallet to tap the hammer gently.
• Remove the target (C) and the plastic
protective cover (D).
IMPORTANT : the order of operations described
below MUST be observed. Not following the
method could cause incorrect operation and / or
damage to the sensor.
2.REFITTING THE CYLINDER REFERENCE SENSOR
Refit :
- the sensor to the cover, push it upwards and
tighten to a torque of 0.15 daN.m,
- the protective plastic cover,
- the target (this has a foolproofing device.
Check its position before fitting to the end of
the camshaft),
- the cover with the sensor. Tighten the three
cover bolts to a torque of 1 daN.m.3.
ADJUSTING THE SENSOR / TARGET GAP
Slacken the bolt mounting the sensor without
touching the sensor then retighten it to a torque
of 0.8 daN.m.
By slackening the bolt the sensor is released. A
spring in the cover pushes the sensor against the
target.
When the bolt is tightened the sensor is secured. It
has two small plastic pips which touch the target.
These pips wear as the engine turns. There is no
longer contact between the two components and
the gap is set.
17-22

INJECTION
Special notes on sequential injection
17
F3R engine
CYLINDER REFERENCE SENSOR CONNECTIONS
TRACK ALLOCATION
1 Earth
2 Information to injection computer on track 42
3 +after ignition
1REMOVAL2REFITTING
DI1701DI1702
DI1703
3ADJUSTMENT
17-23

INJECTION
Injection fault warning light
17
PRINCIPLE FOR ILLUMINATION OF THE INJECTION FAULT WARNING LIGHT ON THE INSTRUMENT PANEL
• Vehicle without engine immobiliser system
When the ignition is turned on, the warning light illuminates for 3 seconds then extinguishes.
• Vehicle with engine immobiliser system deactivated
When the ignition is turned on, the warning light illuminates for 3 seconds then extinguishes.
When the doors are unlocked, the red immobiliser warning light, which was previously flashing, extin-
guishes. When the ignition is turned on, it illuminates for 3 seconds then extinguishes.
• Vehicle with engine immobiliser system activated
When the ignition is turned on, the computer does not identify the code and the vehicle cannot be star-
ted. The injection warning light illuminates for 3 seconds then extinguishes.
Before the ignition is turned on, the red immobiliser warning light flashes. When the ignition is turned
on, this light flashes twice as fast.
If a fault in the immobiliser system is detected when the engine is running, the injection warning light
will flash in the engine speed range from idle speed to 1 500 rpm approximately.
• Fault with an injection system component
Faults in the following components cause the warning light to illuminate:
- absolute pressure sensor,
- throttle position potentiometer,
- injectors,
- idle speed regulation stepping motor (K7M engine),
- idle speed regulation valve (F3R engine),
- no vehicle speed information when the vehicle is moving,
- EGR solenoid valve (K7M 703 engine),
- automatic transmission computer → injection computer (F3R - K7M engines).
17-24

OXYGEN SENSOR VOLTAGE (#05)
Reading #05 on the XR25 : the value read is the voltage sent to the computer by the oxygen sensor; it is ex-
pressed in Volts (the value actually varies between 0 and 1 000 millivolts).
When the engine is in the loop phase, the voltage value should oscillate rapidly and should be between
50±50 mV (lean mixture) and 850 ± 50 mV (rich mixture) and vice versa.
The smaller the gap between the upper and lower oscillating values, the poorer the information from the
sensor (the gap is usually at least 500 mV).
RICHNESS CORRECTION (#35)
The value given under # 35 on the XR25 represents the average value of richness corrections made by the
computer depending on the richness of the burnt mixture as seen by the oxygen sensor (the oxygen sensor ac-
tually analyses the oxygen content of the exhaust gases directly from the richness of the burnt mixture).
The richness correction has a centre point of 128 with thresholds of 0 and 255 (experience has shown that un-
der normal operating conditions # 35 is located close to 128 with only a small amount of variation).
- Value less than 128 : request for mixture to be made leaner
- Value greater than 128 : request for mixture to be made richer
ENTRY INTO RICHNESS REGULATION MODE
Loop phase
Richness regulation begins after the timed starting period :
- for no load if the coolant temperature has reached:
•25°C for E7J engines,
•40°C for K7M engines,
•35°C for F3R engines.
- outside no load conditions if the coolant temperature is greater than :
•+ 20°C for K7M engines,
•+ 15°C for F3R engines,
there is no coolant temperature condition for E7J engines.
The timed starting period is dependent on the coolant temperature:
-at20°C it is a maximum of :
•45 seconds for E7J engines,
•1 minute for K7M engines,
•2 minutes for F3R engines,
-at80°C it is a maximum of :
•9 seconds for E7J engines,
•16 seconds for K7M engines,
•1 minute for F3R engines.
if richness regulation has not yet started,#35 = 128
INJECTION
Richness regulation
17
17-34