MITSUBISHI 3000GT 1991 Service Manual

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LFUEL SYSTEM
- On-vehicle Inspection of MPI Components13405INJECTORS
(Front bank connector)
\/-I- 7FUO80:
3Engine control unit connector
FuelFilter
@Injection
7FUO832Injector
No. 1
coscliio-:Engine
control
unitControl relay@ Equipment side
connector
8
Injector(OscliioJ1Injector
No.5
1
(osclllo)d2
4-(’I
:1
-1
74
----
;3A14
Bris+
5
5----_Injector
-----
2Ioscillo)<
15--60
Rear bank
connector
7FUO973
7FUO653
OPERATION
TROUBLESHOOTING HINTSRefer to “INJECTOR”
(P.13-101).
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13-106FUEL SYSTEM - On-vehicle Inspection of MPI Components
INSPECTION
Using Multi-use Tester
FunctionItem No.Data displayCheck conditionCoolant temperatureStandard value‘L,,,J
DataDrive time*’0°C (32’F)*’readingiRea:bankiEngine: CrankingApprox. 53 ms
(FronT7bank)20°C (68°F)
Approx. 29 ms
80°C (176°F)Approx. 7 ms
FunctionItem No.
Data displayCheck conditionEngine stateStandard value
Datareading(Reaebank)Drive time*3l Engine coolant tem-700 rpm (Idle)1.9 - 2.5 ms
perature: 80 to 95°C
(Front7banki(176 to 205°F)2,000 rpm1.6 - 2.2 ms
l Lamps, electric coolingfan, accessory units:To increase
All OFFWhen sharp racing is
made
l Transaxle: Neutral(P range for vehicle
with A/T)
l Steering wheel: Neutral
NOTE“I : The injector drive time refers to when the supply voltage is 11 V and the cranking speed is less than 250 rpm.
“2: When coolant temperature is lower than 0°C (32°F). injection is made by four cylinders simultaneously.
“3: When the vehicle is new [within initial operation of about 500 km (300 miles)], the injector drive time may be about
10% longer.
Function
Actuator testItem No.
Drive contentCheck conditionNormal state
01No. 1 injector shut offEngine: Idling afterIdle state to changewarm-upfurther (becoming less
02No. 2 injector shut off(Shut off the injectorsstable or stalling)
03in sequence during afterNo. 3 injector shut offengine warm-up, checkthe idling condition)
04No. 4 injector shut off
05
No. 5 injector shut off
06
No. 6 injector shut off
\,iUsing
OscillqscopeI(1) Run the engine at idle speed.
(2) Connect the probe to the oscilloscope pick-up point as
shown in the circuit diagram, and check the waveform at
the drive side of each injector.~
-
LJ
4 AL A: InjectorNormal waveformdrive time03A0209
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-107
HARNESS INSPECTION
@ Harness sideconnector
I
I
7FUO976
Measure the power supply voltage of
the resistor.
l Resistor connector: Discon-
nectedl Ignition switch: ON
connector
7FUO669-I
3Rear bank
harness side
connector
.------------------’7FUO97;
Harness sideconnectorz7FUO805
Measure the power supply voltage of
the front bank injector.
l Resistor connector: Connected0 Injector connector: Disconnected
l Ignition switch: ON
Voltage
(V)
0
OK03
Repair the
harness.
(@g@pJ-Control relay)Check power
supplyCheck resis-tor
Measure the power supply voltage ofthe rear bank injector.l Connector: Disconnected
l Ignition switch: ON
*
04
Repair the
supply’Check resis-tor
Check for an open-circuit, or a short-circuit between the front bank injector
and the engine control unit.
f---l -
l Injector connector: DisconnectedlEngine control unit connector:
Disconnected
1
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13-108
IFUEL SYSTEM
- 0n-vehicle Inspection of MPI Components
------+ Rear bankconnector 1
Check for an open-circuit, or a short-circuit between the rear bank injectorand the engine control unit.l Connector: Disconnected
l
Engine control unit connector:
Disconnected0
OKASTOP
Repair the
harness.
@ilT’ilpt-
iiWF4)
ACTUATOR INSPECTION
INJECTORSMeasurement of Resistance between Front Bank Termi-
nals
(1) Disconnect the injector connector.
(2) Measure the resistance between terminals.
Standard value: 2
- 3 R [at 20°C (68”F)](3) Reconnect the injector connector.
‘iJ
Measurement of Resistance between Rear Bank Terminals
(‘I ) Disconnect the injector connector.
(2) Measure the resistance between terminals.
Standard value: 2
- 3 R [at 20°C (68”F)](3) Reconnect the injector connector.
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13409 ~
n 7FUO949
7FUO97 Measurement of Resistance between Terminals
(1) Disconnect the resistor connector.
(2) Measure the resistance between terminals.
Measuring terminalsResistance
5.5 - 6.5 R[At 20°C (68”F)]
1(3) If the resistance is out of specification, replace the resistor.
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13-110FUEL SYSTEM - On-vehicle Inspection of MPI Components
IDLE SPEED CONTROL SERVO (STEPPER MOTOR TYPE)\
7FUO64;Ball beam
‘9
L PlntleControl relay
@ Harness side
connector
\/1, \,\/“1“3 “4 “6Idle speed
control servo
OSCIIIOOSCIIIOOSClllOosclllomu--
/(a /(IT ),!j /I,, Enginecontrol unit
BPPP
7FUO518Engine control unit connector
7FUO653
OPERATION
lThe intake air volume during idling is controlled by opening ‘or closing the servo valve provided in the air
path that bypasses the throttle valve.’
lThe servo valve is opened or closed by operating the stepper motor in the speed control servo in normal or
reverse direction.
lThe battery power is supplied to the stepper motor through the control relay. As the engine control unit
turns on power transistors in the unit one after another, the stepper motor coil is energized and the motor
rotates in normal or reverse direction.
TROUBLESHOOTING HINTSHint 1:If the stepper motor step increases to 100 to 120 steps or decreases to 0 step, faulty stepper motor
or open circuit in the harness is suspected.
Hint 2: If the idle speed control servo harness and individual part checks have resulted normal but the
stepper motor steps are out of specification, the following faults are suspected.
(I) Poorly adjusted reference idle speed
(2) Deposit on the throttle valve
(3) Air leaking into the intake manifold through gasket gap
(4) Loose EGR valve seat
(5)Poor combustion in the cylinder (faulty ignition plug, ignition coil, injector, low compression
pressure, etc.)
\L.J
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FUEL SYSTEM - On-vehicle .lnspection of MPI Components13-111
INSPECTIONUsing Multi-use Tester
FunctionItem No. Data display
Data reading 45
Stepper
1
motor steps
~
Check condition
l Engine coolant tem-
perature: 80 to 95°C
(176 to 205°F)
0 Lamps, electric cooling
fan, accessory units:
All OFFl Transaxle: Neutral(P range for vehiclewith AA>l Steering wheel: Neutrall Idle position switch: ON(compressor clutch
to be ON if air condi-
tioner switch is ON)l Engine: idling
Load stateStandard value
;;rnditioner switch:2 - 12 stp&conditioner switch:
25 - 65 stp
l $irNconditioner switch:15 - 63 stp0 Selector lever:Shift to D range
NOTEWhen the vehicle is new [within initial operation of about 500 km (300 miles)], the stepper motor steps may be about 30steps more than standard.
CautionWhen the selector lever is shifted to the “D”range, the brakes must be used to prevent the vehicle frommovingforward.
03A020
Using Oscilloscope(1) Connect the probe to each oscilloscope pick-up point as
shown in the circuit diagram.
(2) Start the engine.
(3) When the air conditioner switch is turned on, the idling
speed increases to operate the idle speed control. Check
the instantaneous waveform.
NOTEKeep in mind that the waveform can be observed only
when idle speed control is in operation.
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13-112FUEL SYSTEM - 0
n-vehicleInspection of MPI Components
HARNESS INSPECTION
Measure the power supply voltage ofidle speed control servo.l
Idle speed control servo connec-tor: Disconnectedl Ignition switch: ON
Connector
connector
OlLO395- WI)
Engine control
Check for an open-circuit, or a short-circuit to ground between the enginecontrol unit and the idle speed control
servo.l
Engine control unit connector:
Disconnectedl
Idle speed control servo connec-tar: Disconnected
ACTUATOR I’NSPECTIONChecking the Operation Sound
(1)Check that the operation sound of the stepper motor can be
heard after the ignition is switched ON (but without starting
the motor).
(2) If the operation sound cannot be heard, check the stepper
motor’s activation circuit.
If the circuit is normal, it is probable that there is a
malfunction of the stepper motor or of the engine control
unit.
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idFUEL SYSTEM
- On-vehicle Inspection of MPI Components13-113
‘El
‘a
~
63
7FUOOlO(stepper motor)
7FUO98CIdle speed
MD998463
7FUOO78
Checking the Coil Resistance(1) Disconnect the idle speed control servo connector and
connect the special tool (test harness).
(2) Measure the resistance between terminal @ (white clip of
the special tool) and either terminal @ (red clip) or terminal@ (blue clip) of the connector at the idle speed control
servo side.
Standard value: 28
- 33 !2 at 20°C (68°F)
(3) Measure the resistance between terminal @ (green clip of
the special tool) and either terminal @ (yellow clip) or
terminal @ (black clip) of the connector at the idle speed
control servo side.
Standard value: 28
- 33 CR at 20°C (68°F)
Operational Check(1) Remove the throttle body.
(2) Remove the stepper motor.
(3) Connect the special tool (test harness) to the idle speed
control servo connector.
(4) Connect the positive
0 terminal of a power supply (approx
6 V) to the white clip and the green clip.
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13-114FUEL SYSTEM - On-vehicle Inspection of MPI Components
(5) With the idle speed control servo as shown in the
illustration, connect the negative
0 terminal of the power
supply to each clip as described in the following steps, and
check whether or not a vibrating feeling (a feeling of very
(slight vibration of the stepper motor) is generated as aJresult of the activation of the stepper motor.@Connect the negative
0 terminal of the power supply to
the red and black clip.@Connect the negative
0 terminal of the power supply to
the blue and black clip.@Connect the negative
0 terminal of the power supply to@the blue and yellow clip.
Connect the negative
0 terminal of the power supply to
the red and yellow clip.@Connect the negative
0 terminal of the power supply to
the red and black clip.@ Repeat the tests in sequence from @ to
0.(6) If, as a result of these tests, vibration is detected, the
stepper motor can be considered to be normal.
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