Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 69

EFI - Fuel Syste m
If the engine is cranked when the coolant
temperature is 100°C (212°F) or higher, the
Engine ECU turns on the VSV (the exact
temperature depends on the engine model) .
When the VSV goes on, atmospheric air is
introduced into the diaphragm chamber of the
pressure regulator, causing the fuel pressure to
become higher than that under normal engine
operating conditions . After the engine is started,
the VSV remains on for about two minutes .
There are some engine models in which a water
temperature sensor (THW) is used instead of a
water temperature switch (TSW) .
There are also engines in which other signals
besides the coolant temperature are used in
pressure-up control . These signals include the
intake air temperature (THA) signal, the intake
air volume (VS or PIM) signal, and the engine
speed (NE) signal .
101 .3
(1 kgf/cmz )
0
NOTE
1 . On some recent models, intake manifol d
pressure is not connected to the pressure
regulator .
Fuel pressure is always maintained at a con-
stant pressure higher than the atmospheric
pressure . As a result, changes in injection
volume caused by intake manifold pressure
are corrected by the Engine ECU .
VSV : on
OHP 48
2 . In addition to the models described in 1
above, there are also models in which the
pressure regulator is provided in the fuel
tank . Since there is no fuel return pipe, it
becomes difficult for air bleed once it has
entered the fuel pipe . It is for this reason
that more time is required to start the
engine after the fuel fiiter or similar compo-
nent has been replaced .
6 . INJECTOR S
The injector is an electromagnetically-operated
nozzle which injects fuel in accordance with
signals from the ECU .
Inlet
4
SIDE-FEED TYPE
TOP-FEED TYPE
OHP 4 9
,,--
wv
I
Internal
Resistance of Injector
There are two types of injector, which differ in
their internal resistance level :
• High-resistance type : approx . 13 .8 Q
• Low-resistance type : approx . 1 .5 ^- 3 Sd
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