1991 MITSUBISHI 3000GT Service Manual

FUEL SYSTEM - On-vehicle lnwection of MPI ComDonents
2Measure the power supply voltage ofthe vehicle speed sensor.
@ Harness sidel Connector: Dlsconnectedl Ignition switch: ON
8)
6FU1265l Connector: Disconnected
SENSOR INSPECTIONRefer to GROUP 54
- Meters and Gauges.
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13-80FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
POWER STEERING OIL PRESSURE SWITCHMlOYQAA
B
$-
Engine control unit
'107
@ Harness side
connector
ml-
Power steering oil
Pressure switch
7FUO536700-2.000 1.500-2.000(100-284) (213-284)Pressure [kPa (psi)]
0, l.oIu
OPERATIONl
The power steering oil pressure switch converts presence/absence of power steering load into low/high
voltage and inputs it to the engine control unit, which then controls the idle speed control servo based on
this signal.l The battery voltage in the engine control unit is applied through a resistor to the power steering oil
pressure switch. Steering operation causes the power steering oil pressure to increase, turning the
switch on. As a result, continuity is produced between the battery voltage applied and ground. This
causes the power steering oil pressure terminal voltage to go from high to low.
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FUEL SYSTEM- On-vehicle Inspection of MPI Components13-81
INSPECTIONUsing Multi-use Tester
Function
Data readingItem No. Data displayCheck conditionSteering wheelNormal indication
27Switch stateEngine: IdlingSteering wheel neutralOFFposition (wheels
straight-ahead direction)
Steering wheel half turn
ON
Checking Oil Pressure
Steering wheelOil pump delivery pressure (ref. value)
Straight forward700 - 1,200 kPa (100 - 171 psi)
Turned1,500
- 2,000 kPa (213 - 284 psi)
HARNESS INSPECTION
i1
@ Harness side
connector
Measure the power supply voltage.
SENSOR INSPECTIONRefer to GROUP 37
- Service Adjustment Procedures.
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13-82FUEL SYSTEM - On-vehicle Inspection of MPI Components
AIR CONDITIONER SWITCH AND POWER RELAY
\
*I \\-- \
Air conditronerAir conditioner
control unitAir conditioner
compressor lock
controllerr
Engine control unit
Dual pressureswitch
M13YRAA2
b1IFF
Air conditioner
compressor
Engine control
unit connector
7FUO966
7FUO653
OPERATION
lThe air conditioner switch applies the battery voltage to the engine control unit when the air conditioner is
turned on.
lWhen the air conditioner ON signal is input, the engine control unit drives the idle speed control servo and
turns ON the power transistor. As a result, the air conditioner power relay coil is energized to turn on therelay switch, which activates the air compressor magnetic clutch.
TROUBLESHOOTING HINTS
If the air compressor magnet clutch is not activated when the air conditioner switch is turned on during idling,faulty air conditioner control system is suspected.
INSPECTION
Using Multi-use Tester
AIR CONDITIONER SWITCH
Function1 Item No. 1 Data display 1Check condition) Air conditioner switch 1 Normal indication IData reading 28
Switch stateEngine: Idling (airOFFOFFcompressor to be running
when air conditionerONONswitch is ON)\k”JTSB Revision

FUEL SYSTEM - On-vehicle Inspection of MPI Components
AIR CONDITIONER POWER RELAY
L
FunctionItem No. Data display
Data reading49Air condi-tioner relay
stateCheck conditionEngine: Idling after
warm-up
HARNESS INSPECTIONAir conditioner switch
Normal indication
OFFOFF (compressor
clutch non-activa-
tion)
ONON (compressorclutch activation)
’ I
unit harness
side connector
7FUO695
Measure the power supply voltage of
the air conditioner circuit.l
Air conditioner switch: ONlEngine control unit connector:
Disconnectedl Ignition switch: ON
l
Dual air conditioner switch: ONVoltage
(V)IM
ASTOP
Check the airconditioner
circuit.
AIR CONDITIONER INSPECTIONRefer to GROUP 55
- Service Adjustment Procedures.
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13-84FUEL SYSTEM - 0n-vehicle Inspection of MPI Components
DETONATION SENSOR
Engine control unitN
/J-l
@ Equipment side58: :connectorI I
t- =I IL .J531 5:2::
i SEL1208j
@ Harness side
connector7FU1075
Engine control unit connector
7FUO653
OPERATION
The detonation sensor generates a voltage proportional to the magnitude of cylinder block vibration due to
knocking and inputs it to the engine control unit. Based on this signal, the engine control unit provides retardcontrol of the ignition timing.
TROUBLESHOOTING HINTS
When knocking occurs while driving under high-load conditions, the following problems are suspected inaddition to the detonation sensor itself.
(1) Inappropriate ignition plug heat range
(2) Inappropriate gasoline(3) Incorrectly adjusted reference ignition timing
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-85 1
HARNESS INSPECTION
Check for continuity of the ground
circuit.l Connector: Disconnected
Repair the
harness.
76FU1302
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id

13-86FUEL SYSTEM - On-vehicle Inspection of MPI Components
ELECTRICAL LOAD SWITCH16FO29;
Tail-lightrelayDefog.wrelaystoplight
t;1
switch
ti* . .
Engine control unit connector
Engine
control
unit7FUO653
7FUO688OPERATION
lThe electrical load switch inputs ON/OFF state of the switch of equipment that consumes much powerduring idling, namely, equipment with a large electrical load, to the engine control unit. Based on this
signal, the engine control unit controls the idle-speed control servo.
l
When the switch of equipment with a large electrical load is turned ON, the battery voltage is applied tothe engine control unit to indicate that the equipment switch is turned ON.,
LJINSPECTION
Using Multi-use Tester
Function
Data reading
I
tem No. Data display
-I-
33Switchstate
Check condition
Equipment stateNormal display
$;ration of equipment:L$ing;Atch only:OFF + ON-3
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