1990 MITSUBISHI ECLIPSE crank

FUEL SYSTEM - General14-3The fuel is supplied under pressure by the in-tanksent to the engine control unit.
type fuel pump, and is injected from injectors into allThe crank angle sensor converts the crank
angle,
cders. The injectors are activated by signals fromthat is, engine turning state into an electric signal
tk, engine control unit, and the amount of fueland sends it to the engine control unit.
injected is determined according to the drivingThe engine control unit, based on these signals,
conditions.determines the basic activation timing of the
injec-The intake air passes through the air flow sensor,
tars. The amount of intake air is determined by the
throttle body, air intake plenum and intake manifold,degree of opening of the throttle
valye,, and during
and finally enters the combustion chamber. The airengine idling, the amount of intake
arr IS regulated
flow sensor detects the amount of air flow and
by the idle speed control servo.converts this data to electric pulse signals that are
EGR temperature sensor (California) 7
Waste gate solenoid valve
Purge control solenoid valve
EGR control solenoid valve Fuel pump relay
Control relay
Air conditioner relay
Diagnosis output
Ignition coil
Control relay (Fuel pump drive
signal)Vehicle speed
SensorIgnition switch “ST” terminal
Ignition switch
‘IG” terminal
Air conditioner switch
Power steering
switch
Inhibitor switch
Idle speed
ontrol servoFast idle
air valve
-Throttle
&r -kilo m-i&inn’Power transistorleturn to-
uel tank- Fuel from
Coolant temperature sensor
Coolant temperature switchFuel-pressure
control valve
Detonation sensor
4

14-14
.._~- ---.FUEL SYSTEM
- Sensors
SENSORSRlUGENERAL DESCRIPTION
The types and functions of the sensors are as listedsend corresponding signals to the engine control
below. These sensors detect engine conditions and
unit.
SENSORSFUNCTION
AIR FLOW SENSOR
fSenses the intake arr volume with a Karman vortex flow meter.
INTAKE AIR TEMPERATURE
SENSORSenses the Intake air temperature (temperature of air at
the point of entry into the air cleaner).I
BAROMETRIC PRESSURE
SENSORISenses the barometric pressure faltrtude) wrth a
semiconductor diffusion type pressure sensor.
$;;OOf;T TEMPERATURESenses the engine coolant tern
THROTTLE
POSITISenses the throttle
tI
IDLE POSITION SWITCHSenses whether or not the accelerator pedal is being
operated with a contact switch.
Senses the top dead center on compression stroke of
NO. 1 and No. 4 cylinders with an LED and photo diode pair.
CRANK ANGLE SENSORSenses the crank angle of each cylinder with an LED
and photo diodepair.
T
OXYGEN SENSORSenses
actrvation of the air con
POWER STEERING OIL
PRESSURE SWITCHc-lSenses the power steering ‘load with a contact switch.
IGNITION SWITCHSenses ON/OFF
posrtion of the ignition switch.I
Senses engine cranking.
,
IGNITION TIMING
ADJUSTMENT TERMINALWhen this terminal is shorted, the ignition timing and idle
speed control servo is set in the adjustrng mode by the enginecontrol unit.
INHIBITOR SWITCHSenses the *P” and “N” positthe automatic transaxle.Senses.
by pieto-electric element,. cylinder block
vibrations that occur when there ISengineknocking.
CONTROL RELAY
(Fuel pump drive signal)
lFnorne ianitron sianal!Senses ignrtton coil prIman/ voltage.

FUEL SYSTEM - Sensors
CRANK ANGLE SENSOR
II
DiscSensor
The crank angle sensor is mounted on the cylinder
head and is directly coupled to the intake camshaft.The crank angle sensor consists of a disc -and a
sensor unit.
Mu0499Slit for
crank anglesensor
Photo diode
LED
The disc, made of metal, has four slits located 90 degrees aparton its periphery and two slits located 180 degrees apart inward
of the four slits.
-The inner slits are used by the top dead center sensor
th,detects the top dead center of the No.
1 and No. 4 cylinders,
and the outer four slits are used by the crank angle sensor that
detects the crank angle. The disc is positioned on the sensor
shaft and rotates as a unit with it, being turned by the intake
camshaft.The sensor unit has two
LEDs and two photo diodes, used’to
detect the crank angle sensor slits and the top dead center
sensor slits.
The disc rotates between the
LEDs and the photo diodes. Each
time a slit comes between a LED and photo diode pair, the light
emitted by the LED reaches the photo diode by passing
through the slit.
Sensor unit
I I1
Power supply
I
Engine control untt
r
Crank angleslgnal

--
,
14-24FUEL SYSTEM - Sensors
POWER STEERING OIL PRESSURE SWITCHEngine control unit
Power steering oil
pressure switchBattery
voltage
6FUO5OtIWhen the steering wheel is turned and the oil
pressure of the power steering oil pump increases,
the power steering oifpressure switch sends an ON
signal to the engine control unit. The engine control
unit detects the oil pump load with this signal andactivates the idle speed control servo to control
theidle speed. Specifically, it prevents the idle
speecfrom dropping due to oil pump load, thus
ensuringstable engine idling.IGNITION
SWITCH
1IBattery
Ignition
switch
Starter motor
aS terminalcontrol unit
6FUO762The signal indicating that the ignition switch is ON,
OFF or cranking (ST) is input to the engine control
unit.
When the ignition switch ON signal is input to the
engine control unit, the unit energizes the control
relay coil to supply power to the sensors and
actuators.When the ignition switch ST signal is input to the
engine control unit, it determines that the engine
iscranking and controls the fuel injection rate,
despeed control servo, ignition timing, etc. for
-mum cranking conditions.

I
j:Battery
14-26FUEL SYSTEM - Sensors
INHIBITOR SWITCH The inhibitor switch’s ON (when “N” or
“P”) or OFF (when
other than “N” or
“P”) signals are input to the engine control
unit. The engine control unit, based on these signals, then
determines whether the transaxle is in neutral or is in a drive
range, and then activates the idle-speed control servo so as tc
regulate the idling rpm.
S terminal
---
@
Starter
(Armature)
YT
6FU114!
CONTROL RELAY (Fuel pump drive signal)
This relay senses that power is supplied to the pump.
-If power failed to be supplied to the fuel pump during
er,, .ecranking or during driving, the engine control unit judges that a
fault has occurred and stores corresponding diagnosis code
(No. 42) in memory and at the
sa’me time, causes the engine
alarm lamp (Mulfunction indicator lamp) to come on.IGNITION
COIL (Engine ignition signal)From ignition switchEngine control unit
Ignition
-Elsignal sens-
ing circuit
3)
ffuo573
-
JThis coil senses generating state of the ignition
signal.If abnormal condition occurs during engine
opera-tion such as the ignition signal not being generatedat ignition timing, The engine control unit stores
corresponding diagnosis code (No. 44) in
memoWand at the same time. causes the engine alarm
lamp(Mulfunction indicator lamp) to come on.

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- 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.