Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 67

EFI - Fuel Syste m
ON-OFF CONTROL WITH SPEED CONTROL (BY
ENGINE ECU, FUEL PUMP CONTROL RELAY AND
RESISTOR )
The basic operation of this system is the same
as that of the previously-mentioned on-off type
fuel pump control system, but in this system, the
ECU changes the speed of the fuel pump in two
stages corresponding to the amount of fuel
required by the engine . With this system,
electric power consumption is reduced and fuel
pump durability is improved .
~ At low speed s
When the engine is idling, or under normal
driving conditions (that is, when a small amount
of fuel is satisfactory), the Engine ECU turns on
the fuel pump control relay . The point of this
relay contacts contact B, and the current to the
fuel pump flows through a resistor, causing the
fuel pump to run at low speed .
Fuel pump
control rela y
Engine EC U
c?i At high speed s
When the engine is operating at high speeds or
under heavy loads, the Engine ECU turns off the
fuel pump control relay . The point of this relay con-
tacts contact A, and the current to the fuel pump
flows directly to the pump without passing
through the resistor, causing the fuel pump to run
at high speed .
The fuel pump also runs at high speed while the
engine is starting .
Fuel pump
control rela y
Engine ECU
Fuel
FP pump
®
High
spee d
ON-OFF CONTROL WITH SPEED CONTROL (BY
ENGINE ECU AND FUEL PUMP ECU )
The basic operation of this system is the same as
the types that have been explained thus far . In
this system, however, on-off control and speed
control of the fuel pump is performed entirely by
the Fuel Pump ECU based on the signals from the
Engine ECU .
The Fuel Pump ECU is wired as shown in the
following diagram . Signals from this ECU are used
to switch the fuel pump speed back and forth bet-
ween 2 steps . In addition, the Fuel Pump ECU is
equipped with a fuel pump system diagnosis func-
tion . When trouble is detected, signals are sent
from the DI terminal to the Engine ECU .
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