Mitsubishi 3000GT 1991, Service Manual

Page: 156 / 1146

FUEL SYSTEM 0
n-vehicle Inspection of MPI Components
OPERATION
Control 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 through
the control relay switch to the fuel pump.
l
While 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
l
Change the fuel pump discharge in two stages by ON-OFF operation of the relay switch for fuel pump
relay No. 2.
l
If 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 the
power transistor to send drive power directly to the fuel pump without passing through the resistor.
INSPECTION
Using Multi-use Tester
Pump>
Function
Actuator
test
Item No. Operation Check condition Check item Normal condition
07
Fuel pump is
driven to
l Engine cranking Hold return hose with
l Forced drive of fuel
Pulsation is felt
fuel
fingers to feel pulsation
Check is made for above
indicating fuel flow
two conditions Listen to pump operating
sound near fuel tank
Operating sound is
heard
<Fuel Pump Relay No.
Function Item No.
Operation Check condition Normal condition
Actuator
test 13
Turn the fuel pump relay
No. 2 from OFF to ON
Ignition switch: ON Operating sound
is heard.
HARNESS INSPECTION
l
Apply battery voltage to the
checking terminal and operate the
Check the ground circuit of the fuel
l
Connector: Disconnected
Harness side
connector
L - J
Repair the
harness.
Ground)
TSB Revision