Datsun 1980 200SX Service Manual page 98

ENG IN E FU EL
EFI
System Component
Parts Construction and Function
EFI
SYSTEM COMPONENT PARTS CONSTRUCTION
AND FUNCTION
FUEL FLOW
SYSTEM
FUEL
PUMP
Normal flow
Relief valve actuated
due to
clogged discharge
line
Inl
The fuel
pump
employs
a
wet
type
construction
whe
e a
vane
pump with
roller is
directly coupled
to
a
motor
fIlled with fuel This construction pro
vides
superior coupling
characteristics
between
the
pump
and
motor
and
greater safety
in
case
of fire
RoUer
Outlet
E F252A
Outlet
Fuel pump
relay
Fuel
pump
Battery
El
P i
1
s
1
I
Oilpres
ureswitch
II
Ignition
I
switch
IG
Fuel pump
relay
2
Alternator
Normal
switch
position
IGN SW
position
In the
vane pump
the roller
is
pushed
outward by
centrifugal
force
when the pump rotates
and
is
pressed
against
the
outer
wall This rotary
portion
and
surrounding wall
are
not
coaxial and pumping
is perfonned
by
the
change
in
clearance between
the wall and the
rotary portion
Thus
when the
clearance
is
large fuel
is
sucked
in
when
it
decreases
fuel
is
discharged
The relief valve in the pump is
designed to open
when the pressure in
the fuel line rises
over
294
to 44I
kPa
3
0
to
4 5 kg
cm2
43
to
64 psi due
to
malfunction
in
the pressure
system
The check
valve prevents abrupt
drop
of pressure in
the fuel
pipe
when
stopping
the
engine
Operation
When the ignition switch
is
turned
Nhene ine When nline
opped opEration
Allenulor
L
rmilUll
OLlprclSurt
witch
ON 011
START
No No
ON
generate
pressure
ON Gentrate Normal
ON
ON
Failure NOllTUI1 ON
ON
Gencr atc
Failure ON
ON l a ilure
Fwure OFF
OFF
No
No
OFF
SEF096
teneralt prcuure
Alternator
Oil
Fuel
pump
relay
I
1
pump
Fuel
pump
relay 2
prellure
II Actuate
Actuak
Actuate
Actuate
No
actuate
No
actuate
to the
START
position
for
cranking
operation
the fuel pump
is
actuated
irrespective
of the
conditions of
the
alternator and
the
engine
oil pressure
swjtch
After starting
the
engirie the igni
tion
switch is ON
the alternator
operates
and
the engine
oil pressure
switch is open
through
rotation of the
engine th reby
actuating the fuel
pump
If the alternator stops and the
en
gine
oil pressure decreases for
some re
ason
the fuel
pump
relay
2
contact is
turned
to
II
and the fuel
pump
relay l is turned OFF
Then the fuel
pump is
stopped through
the
ignition
switch remains
in
the
ON
position
In this
manner
fuel supply is cut
off
for safety purposes when the engine
accidentally
stops
during driving
EF l1