1991 MITSUBISHI 3000GT Service Manual

FUEL SYSTEM- Ori-vehicle lnwection of MPI ComDonents13403
+/A+ A: Injector drive time
Normal waveform03A0201
HARNESS INSPECTION
--J1
Harness side
7FlJO669
* I
@
Harness side
connector
1 HarnessJPside =connector7FUO805
Using Oscilloscope
(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.
Measure the power supply voltage of
the front bank injector.
-
l Connector: Disconnectedl Ignition switch: ON
1
Repair the
harness.
(m-Control relay)
Measure the power supply voltage ofthe rear bank injector.
l Connector: Disconnectedl Ignition switch: ON
Voltage
(VI
svRepair the
harness.
(m - Con-
trol relay)
Check for an open-circuit, or a
short-circuit between the front bank injectorand the engine control unit.
l Injector connector: DisconnectedlEngine control unit connector:
Disconnected
id
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13-104FUEL SYSTEM - On-vehicle Inspection of MPI Components
-l4Harness side
connector
L----.[ Q1J
7FUO971
‘Y-4 ’onnector for
7FUO78C
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:
Disconnected
I
ACTUATOR INSPECTIONMeasurement of Resistance between Front Bank Termi-
nals(1) Remove the injector connector.
(2) Measure the resistance between terminals.
Standard value: 13
- 16 il [at 20°C (68”F)](3) Install the injector connector.
Measurement of Resistance between Rear Bank Terminals
(I) Remove the injector connector.
(2) Measure the resistance between terminals.
Standard value: 13
- 16 Q [at 20°C (68”F)](3) Install the injector connector.
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L
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.)
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