Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 65

EFI - Fuel Syste m
2 . FUEL PUMP CONTRO L
The fuel pump in a vehicle equipped with an EFI
engine operates only when the engine is
running . This is to prevent fuel from being
pumped to the engine when the ignition switch
is on but the engine is stopped .
The following types of fuel pump control are in
use at present :
On-off
contro l
Fuel pump
control
method
L
I On-of f
L control
with
speed
control
By Engine EC U
By fuel
pump switc h
By Engine ECU,
fuel pump control
relay and resistor
By Engine ECU
and fuel pump
EC U
ON-OFF CONTROL (BY ENGINE ECU) *
1)
Engine crankin g
When the engine is cranking, current flows from
the IG terminal of the ignition switch to the Li
coil of the EFI main relay, turning the relay on .
At the same time, current flows from the ST
terminal of the ignition switch to the L3 coil of
the circuit-opening relay, turning it on to operate
the fuel pump .
Battery
The starter operates next and the engine begins
to crank, at which point the Engine ECU receives
an NE signal . This signal causes the transistor
inside the Engine ECU to go on, and current
therefore flows to the L2 coil of the circuit-
opening relay .
~2 Engine started
After the engine sta rts and the ignition switch is
returned from the START position ( ST terminal)
to the ON position (IG terminal), current flowing
to the L3 coil of the circuit-opening relay is cut
off . However, current continues to flow to the L :
coil, while the engine is running, due to the
transistor inside the Engine ECU being on . As a
result, the circuit-opening relay stays on,
allowing the fuel pump to continue operating .
($)
Engine stopped
When the engine stops, the NE signal to the
Engine ECU stops . This turns off the transistor,
thereby cutting off the flow of current to the L2
coil of the circuit-opening relay . As a result, the
circuit-opening relay turns off, turning off the
fuel pump .
D-EFI systems and L-type EFI with optical Kar-
man vortex type air flow meter or hot-wire
type air flow meter .
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