Mitsubishi 3000GT 1991 Service Manual page 156

FUEL SYSTEM - 0
OPERATION
Control Relay Operation
Drives the fuel pump during cranking and engine operation.
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When the ignition switch is set to START, current flows from the ignition switch through the control relay
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coil to ground. This turns on the control relay switch and drive power is supplied from the battery through
the control relay switch to the fuel pump.
While the engine is running, the engine control unit keeps the power transistor on and energizes the
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control relay coil so that drive power is supplied to the fuel pump.
Fuel Pump Relay No. 2 Operation
Change the fuel pump discharge in two stages by ON-OFF operation of the relay switch for fuel pump
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relay No. 2.
If the amount of inlet air is small (the engine load is low), the engine control unit turns on the power
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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 the
power transistor to send drive power directly to the fuel pump without passing through the resistor.
INSPECTION
Using Multi-use Tester
Function Item No.
Actuator 07
test
<Fuel Pump Relay No. 2>
Function Item No.
Actuator
test
HARNESS INSPECTION
connector
L -
n-vehicle Inspection of MPI Components
Operation Check condition
Fuel pump is l Engine cranking
driven to cir- l Forced drive of fuel
Check is made for above
two conditions
Operation
13 Turn the fuel pump relay
No. 2 from OFF to ON
Apply battery voltage to the
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checking terminal and operate the
Check the ground circuit of the fuel
Connector: Disconnected
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J
Check item
Hold return hose with
fingers to feel pulsation
indicating fuel flow
Listen to pump operating
sound near fuel tank
Check condition
Ignition switch: ON Operating sound
is heard.
Normal condition
Pulsation is felt
Operating sound is
heard
Normal condition
Repair the
harness.
Ground)