coolant temperature MITSUBISHI ECLIPSE 1990 User Guide

14-18FUEL SYSTEM - Sensors
tBAROMETRIC PRESSURE SENSOR
Barometnc rxessure sensor
EC1537
Barometncpressure sensor
Enginecontrol unit
1OFUO576
/
760 (30)Barometric pressure mmHg
(in.Hg)EC1551A barometric pressure sensor is
alas mounted on
the
aif flow sensor. It senses the barometric
pressure and converts it to electrical voltage which
is sent as a signal to the engine control unit.
Using this signal, the engine control unit calculates
the altitude
of.the location where the vehicle is, and
corrects the fuel injection quantity for the optimum
air-fuel ratio at that altitude, and also corrects the
COOLANT TEMPERATURE SENSOR
Terminal 26EL0069ignition timing.
This ensures improved driveability at high altitudes.
The barometric pressure sensor converts the pres-
sure to a voltage making use of the fact that the
resistance of a strain gauge changes in direct
proportion to the pressure as shown in this diagram
which
illustratestherelationship between
barometric pressure and output voltage.
Engine control unit
Coolanttemperature
sensor
-a
Tg-I
h-esI
*
5 volts
LizIdr
tSFUOLSL
L0 (32120 (68)Coolant temperature -The engine coolant temperature sensor installed in
the coolant passage of the thermostat case is a
thermistor whose resistance changes with the
engine coolant temperature.
The
annine control unit iudoes the enoine warm UDstate based on the output voltage of this sensor and
provides optimum mixture enrichment when the
engine is cold.
The sensor characteristics are as shown above..:I

‘7JFUEL SYSTEM
- Sensors14-23AIR CONDITIONER SWITCH
Batten/
-31 .,Air conditioner unitlSAO735‘Air conditioner
control unitI”.._. ,voltage
Dual pressureswitch
-f@ -//Q.j
/
Coolanttemperature6FU1148
switch
Engine control unit
3Air conditioner
This switch sends the air conditioner ON/OFF signal
to the engine control unit.
When the air conditioner is turned on and the enginecontrol unit receives the ON
signal from the switch,
it commands the idle speed control servo
toincrease the idle speed to the preset rpm. Thus
engine rpm loss due to air conditioner operation
while the engine is idling is prevented and smooth
idling operation is ensured.

FUEL SYSTEM- Engine Control Unit14-29
SFUllSOTerminal
ConnectionTerminalConnectionNo.
No.
1Self-diagnosis output53EGR control solenoid valve (California only)
2Diagnosis/data transfer select terminal54Power transrstor for No. 1 and No. 4 cylinder
‘3Turbo meter
55Power transistor for No. 2 and No. 3 cylinder
4Oxygen sensor56Control relay (Fuel pump control)
5Power steering oil pressure switchl 57Fuel-pressure control valve
6Idle position switch58Coil “Al ” for idle speed control servo
7Air conditioner switch59Coil “A2” for idle speed control servo
8Intake air temperature sensor60No. 3 injector
l 9Detonation sensor61No. 4 injector
10Air flow sensor62Purge control solenoid valve11
-63Control relay
12Ignition timing adjustment connector64Engine warning irght (Malfunction indicator light)
13Control relay (Fuel pump drive signal)65Air conditioner relay
l 14Air flow sensor active filter reset66Control relay
15EGR temperature sensor (California only)67Coil “Bl ” for idle speed control servo
16Barometric pressure sensor68Coil “B2” for idle speed control servo
17Sensors ground101Ground
18Vehicle speed sensor102Power supply
19Throttle position sensor103Power supply for backup
20Coolant temperature sensor
104Inhibitor switch
21Crank angle sensor‘105
Waste gate solenoid valve
22Top dead center sensor106Ground
23Power supply for sensors (5 volts)107Power supply
24Sensors ground108“ST” terminal for ignition switch
51No. 1 injector109Ignition pulse detect
52No. 2 injector170“IG ” terminal for ignition switch
NOTETerminals indicated by the l symbol are applicable only to turbo models.

14-30SELF-DIAGNOSISFUEL SYSTEM- Engine Control Unit
There are 16 diagnosis items, as listed below; the
diagnosis results are stored in computer memory.The diagnosis memory is maintained by backup
The stored results can be ready by connecting apower from the battery (not by way of the ignition
circuit tester or voltmeter to the diagnosis
connec-switch) so that it will not be lost even if the ignition
switch is turned OFF.
tor.
DiagnosisOutput pattern
codeEl
None
lP
@ 11l-l
@ 12n@ 13
@ 14
@ 21Ul n
Diagnosis items
Faulty computer in the engine control unitMalfunction of the air/fuel ratio control system
Open or short circuit in the oxygen sensor circuit
Open or short circuit in the air flow sensor circuit
Open or short circuit in the intake air temperature sensor
circuit
Open or short circuit in the throttle position sensor circuit
Open or short circuit in the engine coolant temperature sensor
circuit
022u1 nn
No voltage change of the crank angle sensor signal
,
@
23
u u-inn
No voltage change of the TDC sensor signal
24uu-uvinnnnNo voltage change of the vehicle speed sensor signal
Q25uuuuuunnnnnOpen or short circuit in the barometric pressure sensor
2 31I-~-~---~ nOpen circuit in the detonation sensor circuit
@ 41uuul nOpen circuit in the injection circuit
042UUuLJul
Malfunction of the control relayOpen or short circuit in the fuel pump drive circuit
z 43UUULnlulMalfunction of the
EGR system
Open or short circuit in the EGR temperature sensor circuit
%4u u u uvinnOpen circuit in either of ignition coil circuit
0nNormal (with none of above faults)
. IA-r-NUltl 1: l 2: for California@ denotes items indicated by an illuminated engine warning light

__.-~-..- -
FUEL SYSTEM- Ermine Control Unit
FAIL-SAFE AND BACKUP FUNCTiON
(1) The fail-safe function controls the system so
that passenger and vehicle safety can be
maxi-
mized. in the event of failure of sens.ors or other
parts.If a sensor related to
ISC fails, for example, the
engine control unit is programmed to prevent
sharp increases in the engine speed.(2) The backup function of the engine control unit
ignores the output signal of a failed sensor and
instead uses a built-in program or set of values
so that the vehicle may continue to function. The
operating state when the backup function is
being used, is termed the emergency mode, and
the engine, control unit keeps the engine warn-
ing light ON during this mode.
Fail-safe/Backup Function
Control contentsFaulty system
Fuel injection control
Idle speed controlIgnition timing control
Air flow sensor
Uses throttle position sensorFixes stepper motor atUses throttle position sensorsignal for control.
position wider than idle.signal for control.
Intake air
temper-Provides control with intake
Provides control with intakeProvides control with intake
ature sensorair temperature assumed to
be 25°C (77°F).air temperature assumed toair temperature assumed tobe 25°C (77°F).be 25°C (77°F).Throttle position
-Does not perform driving and-sensor
acceleration/deceleration
control.
Engine coolantProvides control with engine
Provides control with engineProvides control with engine
temperaturecoolant temperature
coolant temperaturecoolant temperature
sensorassumed to be 80°C (176°F)assumed to be 80°C (176°F).assumed to be 80°C (176°F).BarometricProvides control with
baro-Provides control with baro-Provides control with baro-pressure sensormetric pressure assumed to
be 760
mmHg (30 in.HgI.metric pressure assumed tometric pressure assumed tobe 760 mmHg (30 in.Hg).be 760 mmHg (30 in.Hg).Detonation sensor
-Retarded about 3 degree.Ignition coil
Fuel not injection to a cylinder-whose ignition signal is
abnormal.
TDC sensorOxygen sensor
No fuel injection.-
Feedback control of air/fuel-
ratio by oxygen sensor signal
is not made.

FUEL SYSTEM- Fuel Injection Control14-33
FUEL INJECTI& CONTROLGENERAL DESCRIPTION
Air flow sensor
cBarometric Dressure sensor
Coolant
temr3erature sensorITop dead center sensor
ignition switch
-
c
6FUO569The engine control unit activates the injectors andFuel is injected into each cylinder sequentially, and
controls the fuel injection rate in response. to thetakes place once for each cylinder every two
sensor information so that the optimum
air/fuel ratiorevolutions of the crankshaft. The injection duration
can be maintained at all times under ever-changing(namely the injector activation time) is the basic
engine operating conditions. The fuel injection rateactivation time determined according to the intake
is determined by the injection frequency corres-air volume of each cylinder, with corrections applied
ponding to the engine speed, and by the injectionaccording to the intake air temperature, engine
duration corresponding to the intake air volume.coolant temperature and other factors.

-
14-34FUEL SYSTEM - Fuel Injection Control
TDC sensorAir flow sensor
I
Reading of input signal1
I ,,
uOperation mode decisionOperation mode decision data
I rBasic valve opening time data
Enginecontrol unitInjector activation time control
Injector activation pulse generationControl factor data of
engine coolant temperature,
intake air temperature and
barometric pressure, etc.
Injector1
6FUO766Needle valveFilter
Connector
Solenoid coil
Plunger
-4
INJECTOR,
The injection nozzle spray opening area is constant and the fuelinjection pressure is also constant; therefore, the injection
quantity is determined by the amount of time that the solenoid
coil is energized.
.

FUEL SYSTEM- Fuel Injection Control14-39FUEL INJECTION AMOUNT CONTROL (INJECTOR ACTIVATION DURATION CON-
TROL)
bntrol during Normal Operating Conditions
Open loop control
( ArrflowsensorBasic driving
time deter-
-”mination
i( Injected fuel
amount control
s depending on
engine coolant
temperature
I
II
””compensatron
Injected fuel Injected fuel
c amount control t-c amount control t-during accel-during accel-4 4eration and eration anddeceleration decelerationIIInjector Injector
+ Batten/voltage --W+ Batten/voltage --Wcompensation compensation
QQ44=I,=I,f \f \6FU07M6FU07Mtemperature
II
The injector activation duration is determined
basi-
tally by the intake air flow signal from the air flow
sensor and the crank angle signal (engine rpm
signal). The duration determined in this way is called‘le “basic activation duration”. A correction factor is
applied to the basic duration according to the signalsfrom various sensors, to obtain the optimum
injec-tor activation duration (fuel injection volume) for
current driving conditions.

FUEL SYSTEM -Fuel Injection Control
14-41
During normal operation (including idling), the en-
gine control unit controls the injector activation time
tcThieve the stoichiometric air/fuel ratio, which
e.;res maximum efficiency of the catalytic conver-
ter, on the basis of the oxygen sensor signal.
When the air/fuel mixture is richer than the
stoichiometric ratio, there is less oxygen in the
exhaust gas and thus the oxygen sensor output
voltage is higher; hence a “mixture rich” signal is
input to the engine control unit. Then, the engine
control unit decreases the amount of fuel injected. If
the air/fuel ratio decreases to the point that and the
mixture becomes leaner than the stoichiometric
ratio, the oxygen concentration in the exhaust gas
increases and the oxygen sensor output voltage
becomes lower. Then, a “mixture lean” signal isinput to the engine control unit.
Upon input of this signal, the engine control unit
increases the feedback correction factor, thus caus-
ing more fuel to be injected.
By means of the above-mentioned controls (collec-
tively called “feedback control”), the air-fuel mixture
is maintained at the stoichiometric ratio.
Under the following specific conditions, this feed-
back control is not performed, in order to improve
driveability.
(11
(2)
::I
(5)While cranking the engine
During engine warm-up when engine coolant
temperature is less than
45°C (113°F)During acceleration/deceleration
During high load operation
When oxygen sensor is not functioning
IOPEN LOOP CONTROL
Engine speed rpm6FUO274
II
80(176)
Coolant temperature “C (“Fj6FlJO276
I425(77)
Intake air temperature “C (“F)1~40,0IThe amount of fuel injected is controlled according to the map
value* preset for each engine speed and A/N (refer to
P.l4-39FOR YOUR INFORMATION).
*Map value: Value preset and stored in the ROM of the engine
control unit.
ENRICHMENTWhen the throttle valve is wide open, control is performed to
increase the amount of fuel injected, in order to secure good
driveability under high load conditions.
FUEL INJECTION CONTROL DURING ENGINE WARM-UP
To secure good driveability when the engine is still cold, control
is performed to increase the amount of fuel injected when the
engine
cooiant temperature is low.
FUEL INJECTION CONTROL ACCORDING TO INTAKE AIR
TEMPERATUREGiven a constant intake air volume, the change in intake air
temperature alters the intake air density, resulting in an
improper air-fuel ratio.
To correct this deviation, the amount of fuel injected is
controlled; i.e., the amount of fuel injected is increased to
compensate for the higher
intake air density caused by the
decreased intake air temperature.

14-42
FUEL SYSTEM- Fuel Injection Control
4
Fz.or.c
4:0/
E
{!*760 (301Barometric pressure
mmHg (in.Hg) 6Fuo9z
c
Timet
6FUO279Drivecurrent
0: bri
F2JJ’ ipe; II
I+-JValve opening timi16240:
E‘C
F
.-
is
3
3:\Battery voltage
V162406
80 (176)Coolant temperature
“C (“F)162401HIGH ALTITUDE COMPENSATION
A change in barometric pressure, which may be caused by
change in altitude, alters the intake air density, resulting in an
improper air-fuel ratio. To compensate this deviation, the
amount of fuel injected is controlled; i.e., the amount of fuel
injected is decreased to compensate for the lower intake air
density caused by the decreased barometric pressure, or the
higher altitude.
CONTROL FOR FUEL ENRICHMENT DURING ACCELERA-
TIONDuring acceleration at low and middle loads, fuel supply rate is
increased to improve acceleration performance.
FUEL DECREASE CONTROL DURING DECELERATION
During deceleration, fuel supply rate is decreased to improve
fuel economy.
BATTERY VOLTAGE COMPENSATION
As described earlier in “INJECTOR”, the needle valve of the
injector is pulled to the fully open position when current flow-
through the solenoid coil. This means that there is a time I;
between the time when the current starts flowing and when
the needle valve starts opening. This time lag is called the dead
time.
The dead time varies with different battery conditions:: the
lower the battery voltage, the longer the dead time.
Since the injector activation duration depends on the intake air
volume and other factors, a longer dead time means a shorter
activation duration, or a smaller amount of fuel injected. This
results in an improper air-fuel ratio. At such times, the solenoid
coil is energized for a longer period of time depending on the
current battery voltage to correct the valve opening time, thus
ensuring that the optimum amount of fuel is injected.
Fuel Injection Control at Starting
When the engine is cranked, the map value preset according to
the engine coolant temperature is used as the basic injector
activation duration, to which the high altitude compensation is
applied..