engine MITSUBISHI 3000GT 1991 Service Manual

13-40FUEL SYSTEM -On-vehicle Inspection of MPI Components
COMPONENTS INSPECTION PROCEDUREM13YBAC
USING MULTI-USE TESTER
(1) Check by the service data and actuator test function. If any ij
abnormality is found, check the body harness, components,
etc. and repair as necessary.
(2) After repair, check again with the multi-use tester to makesure that the input and output signals are now normal.
(3) Erase the self-diagnosis trouble code in memory.
(4) Disconnect the multi-use tester.
(5) Start the engine and perform running test, etc. to make
sure that the troubles have been corrected.
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-41
POWER SUPPLY AND IGNITION SWITCH-IG
Engine control
unit
16FO29:
Q-i=++=
iA MPI control relay
ml3Yuu
lcmition switch (IG)
@ Harness sideccmnector
62
I
Engine control unit
Engine control unit connector7FUO950
OPERATIONl
While the ignition switch is on, battery power is supplied to the engine control unit, the injector, the airflow sensor, etc.
lWhen the ignition switch is turned on, the battery voltage is applied from the ignition switch to the engine
control unit, which then turns ON the power transistor to energize the control relay coil. This turns ON thecontrol relay switch and the power is supplied from the battery to the engine control unit through the
control relay switch.
INSPECTION
Using Multi-use Tester
IFunctionItem No.Data displayICheck conditionIStandard valueI
Data reading16Engine control unit
power voltageIgnition switch: ONsv
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IS-42FUEL SYSTEM - On-vehicle Inspection of MPI Components
HARNESS INSPECTION
Measure the ignition switch terminalinput voltage.l
Engine control unit connector:
Disconnectedl Ignition switch: ON
01
orOlLO427Voltage
(V)svRepair the
harness.
(Ignitionswitch -@I
Measure the power supply voltage ofthe control relay.l Connector: Disconnected
Voltage
(V)sv
Repair the
harness.
(Battery -
@IIN
ontrolrelay connector: Discon-
Engine controlunit harnessCheck for an open-circuit, or a short-
side connectorcircuit to ground between the enginecontrol unit and the control relay.l
Control relay connector: Discon-l
Engine control unit connector:
Disconnected
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13-44FUEL SYSTEM - On-vehicle Inspection of MPI Components
ENGINE CONTROL UNIT POWER GROUNDMlBYD~
wEngine controld/ unii16FO292
Engine control unit
L-7-l d
1326
Yx
01A01@1
Engine control unit connector
7FUO653
OPERATIONGrounds the engine control unit
TROUBLESHOOTING HINTSIf the ground wire of the engine control unit is not connected securely to ground, the unit will not operate
correctly.
HARNESS INSPECTION
unit harness
side connector
Check for continuity of the ground
circuit.l
Engine control unit connector:DisconnectedTSB Revision

FUEL SYSTEM -On-vehicle Inspection of MPI Components13-45
FUEL PUMP
@ Equipment side
connector
@ Harness side
connector
lqnition switch (IG,i
LL--- /A&
\“// //@JFuel pump connector
Engine control unit connectorEquipment
connectorside
@ Harness side
connector
7FUO653
7FUO952
M13YEAA2
OPERATIONl Drives the fuel pump during cranking and engine operation.
lWhen the ignition switch is set to START, current flows from the ignition switch through the control relay
coil to ground. This turns on the control relay switch and drive power is supplied from the battery throughthe control relay switch to the fuel pump.
lWhile the engine is running, the engine control unit keeps the power transistor on and energizes the
icontrol relay coil so that drive power is supplied to the fuel pump.
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13-46FUEL SYSTEM - On-vehicle Inspection of MPI Components
INSPECTIONUsing Multi-use Tester
FunctionItem No.DriveCheck condition
Check contentNormal statedActuator test 07
Fuel pump isl Engine cranking
Hold return hose withPulsation is felt
driven to cir-l Forced drive of fuelculate fuelfingers to feel pulsation
pump
Check is made forindicating fuel flow
above two conditions
Listen to pump operating
sound near fuel tankOperating sound isheard
HARNESS INSPECTION
check terminal
7FUO954
@ Harness side
connector7FUO955
Check the fuel pump.l
Apply battery voltage to thechecking terminal and operate the
w-w
Check for continuity of the ground
circuit.l
Fuel pump connector: Discon-
nected
Repair the
harness.
@FJ-Ground)
Check for continuity between the fuelpump and the checking terminal.l
Fuel pump connector: Discon-
nectedcl4
Repair the
harness.
@vJ-@g)
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FUEL SYSTEM - On-vehicle inspection of MPI Components
@ Harness side
connector6
1
@ Harness side
connector
77FUO475
-
Engine controlunit harnessside connector
Q Harness side
-1
=7FUO476
9 Harnessside
connec-
tor
@ Harness side connector
7FUO956
Measure th& power supply voltage of
the control relay.l Connector: Disconnected
OK
lIgnition switch: START (when0
@@checked)lIgnition switch: ON (when @@
checked)
cl6
t
Repair the
harness.
(Ignition
switch-[IGI
- @El)
(Ignition
switch-[ST]
- @El)
Check for an open-circuit, or a short-
circuit to ground between the controlrelay and the engine control unit.
lControl relay connector: Discon-nectedl Enaine control unit connector:
Disconnected
Repair the
harness.
@El-lg
Check for continuity of the ground
circuit.l Connector: Disconnected
Repair the
harness.
L%n~)
Check for an open-circuit, or a short-circuit to ground between the controlrelay and the fuel pump.A
lControl relay connector: Discon-nected(OK)+ Adl Fuel pump connector:
Discon-netted
Repair the
harness.
@I@-@g)
I
vision

FUEL SYSTEM - On-vehicle Inspection of MPI Components
13-49 i
Ignition switch [IG]
Ignition switch [ST]
@ Equipment side
connector9 3Control reta)
;i.
L Ll
@ Harness side
connector
Enaine control unitEquipment side
connector
M-ii
Resistorw(for fuel pump)
Equipment side
connector
II &A
8 A21
@ Equipment
side@I Harness side
connector
connector
M
‘r
Y
2
7
Y
Fuelpump
-JFuel pumpcheck terminal
7FUO959Engine control unit connector
7FUO653
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13-50FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
OPERATIONControl Relay Operation
l Drives the fuel pump during cranking and engine operation.
l
When the ignition switch is set to START, current flows from the ignition switch through the control relay
coil to ground. This turns on the control relay switch and drive power is supplied from the battery throughthe control relay switch to the fuel pump.
lWhile the engine is running, the engine control unit keeps the power transistor on and energizes the
control relay coil so that drive power is supplied to the fuel pump.
Fuel Pump Relay No. 2 Operation
lChange the fuel pump discharge in two stages by ON-OFF operation of the relay switch for fuel pumprelay No. 2.
lIf the amount of inlet air is small (the engine load is low), the engine control unit turns on the power
transistor to energize the coil of fuel pump relay No. 2, sending drive power to the fuel pump through the
resistor. If the amount of inlet air is large (the engine load is high), the engine control unit turns off thepower transistor to send drive power directly to the fuel pump without passing through the resistor.
INSPECTIONUsing Multi-use Tester
Function
ActuatortestItem No.
Operation
Check conditionCheck itemNormal condition
07Fuel pump isdriven to cir-l Engine crankingHold return hose withl Forced drive of fuelPulsation is felt
culate fuelfingers to feel pulsationpump
Check is made for aboveindicating fuel flow
two conditionsListen to pump operating
sound near fuel tankOperating sound isheard 2>
I/IIII
cFunctionItem No.Operation
Check conditionNormal condition
Actuatortest
13Turn the fuel pump relayNo. 2 from OFF to ONIgnition switch: ONOperating soundis heard.
HARNESS INSPECTION
k
J------ 7FUO953
lApply battery voltage to thecheckingterminal and operate the
Check the ground circuit of the fuel
pump.
l Connector: Disconnected
@I Harness side
connectorL-J
7FUO554
Repair the
harness.
@pJ-Ground)
J
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FUEL SYSTEM- On-vehicle Inspection of MPI Components13-51
Check for continuity between the fuelpump and the checking terminal.-I
l Connector: Disconnected
@N+ 14
Repair the
harness.
(@lig-@g)
@ Harness srdeconnector7FUO95:
Check for continuity between thechecking terminal and the control re-
lay (for fuel pump), and between the
resistor (for fuel pump).
0Control relay (for fuel pump) con-nector: DisconnectedlResistor (for fuel pump) connec-tor: DisconnectedlFuel pump connector: Discon-
nected
Harness side
connector
7FUO960
0
OK
Repair the
harness.
(Cm- Da)!~m-- E@J)8 8
Enaine controlCheck for an open-circuit, or a short-circuitto ground, between the controlrelay (for fuel pump) and the enginecontrol unit.
0Control relay (for fuel pump) con-nector: Disconnected
un? harness
side connector
lEngine control unit connector:
DisconnectedRepair the
harness.
(@J-m@ Harness side
connector
Check for continuity between thecontrol relay (for fuel pump) and the
resistor (for fuel pump).
0Control relay (for fuel pump) con-nectar: Disconnectedl Resistor (for fuel pump) connec-tor: DisconnectedRepair the
harness.
(@pJ-@iJ)
7FUO962
Measure the power supply voltage ofthe control relay.
@I Harness side
connector
rl Connector: DisconnectedlIgnition switch: START (when
checking
@@IlIgnition switch: ON (when check-
ing
@@IVoltage
(VI8 or higher
1 ‘7FUO47fITSB Revision