Fuel System; Fuel Tank Replacing; Furl Pump Testing - Datsun 510 series Workshop Manual

Fuel
System
DESCRIPTION
FUEL TANK
FUEL PUMP
CARBURETTOR IDLING ADJUSTMENT
FAST IDLE OPENING ADJUSTMENT
THROTTLE VALVES INTERLOCK OPENING
DASHPOT
DESCRIPTION
The
diaphragm type fuel pump shown
in
Fig D 1
feeds
fuel from the
tank to
the carburettor
in
a
regulated supply
according
to
the needs of the
engine
A
cartridge type fuel
strainer prevents
any
dirt from
reaching
the pump inlet valve
The
carburettor fitted
to
the engine
is either
a
down
draught
two
barrel type equipped with
a
throttle operated
acceleration pump and
power
valve mechanism
See
Fig
D 2
or a
twin
SU carburettor of the type shown in
Fig
D 3 In the
two
barrel type
carburettor
fuel flows from the passage
at
the
bottom of the float chamber passes through the primary
main
jet
and mixes with air introduced
through
the main
air bleed
screw
The petrol and air mixture
is injected
into the venturi
through the main nozzle
Each
time
the accelerator
pedal
is
depressed
the throttle
opens
and the accelerator pump forces
a
jet
of
petrol
into the
air
stream to
allow the engine
to
accelerate smoothly See Fig
0 4
The power valve mechanism is
operated automatically
according to
the demands made
by
the
engine
Under
light
load
i
e
part throttle conditions the intake manifold
depression
is
transmitted below the throttle valve the vacuum
pulls
a
piston
upwards against
a
spring and leaves the power valve closed
allowing
additional air to be admitted
through
the air bleed
screw
and
thereby
weaken the
petrol
and air mixture When the
vacuum
below the throttle vaJve is lowered during
full load conditions
the piston is pushed down
opening the power valve and
providing
additional fuel
to
enrichen the mixture
The
model
HJ L 38W6 SU twin carburettor is of the
horizontal variable venturi
type
and is used only
on
the 1600
and 1800
cc engines
In this
type
of carburettor
a constant
flow of intake
air is
maintained by the
automatically adjusted
venturi
opening this is
accomplished by the suction piston
sliding
in accordance with
changes
in the volume of intake
air
Referring to Fig
D 5 the suction chamber is mounted above
the venturi The suction piston slides
vertically within the
chamber and
changes
the venturi opening
area
The piston is
operated by
a
difference between the upper
vacuum
pressure
which is applied through the suction poct and the
atmospheric
pressure which is introduced through the air hole from the air
cleaner
The
amount by
which the throttle is
opened
causes
the
suction piston
to
rise
or
fall under the intluence of the
engine
suction The pozzle
opening
therefore changes and provides
an
optimum
air fuel mixture
at
all
engine speeds
The cartridge type fuel strainer utilizes
a
fibre strainer
element which should be
replaced
every
20 000 km 12 000
miles Removal of the fuel strainer is
a
simple operation but
as
it cannot
be drained the strainer should
not
be removed when
CARBURETIOR Removal and Overhaul
FLOAT LEVEL
Adjustment
SU TWIN CARBURmORS Adjustments
SU TWIN CARBURmORS Dismantling
SU TWIN CARBURETTORS
Inspection
STARTING INTERLOCK VALVE OPENING
HYDRAULIC DAMPER
the tank is full unless
absolutely
necessary
A viscous paper
type
air cleaner element is fitted which
does
not
require cleaning and should be repl ced every 40 000 km
24 000 miles The
air
cleaner fitted
on
the single carburettor
is
equipped
with
an
idling
compensator
to
prevent
the mixture
from
becoming
too rich at
high idling temperatures
Additional
fresh air is introduced into the inlet manifold
by
the
action of
a
bimettalic strip
located in the air cleaner When the
temperature
under the bonnet is
high
the bimetal
is
heated by
the hot inlet
air
and lifts
to
allow the valve
to
open The
idling compensator
valve partially
opens at
550
I310F
and is
fully
open at 650C
l490F The unit
cannot
be dismantled
as
it is pre sealed and
correctly adjusted for valve
timing Fig D
6
shows the layout
of the
idling
compensator
piping
FUEL TANK Replacing
The fuel tank
can
be removed in the
following
manner
Remove the
rear
seat
and back
rest
2 Take out
the board behind the back
rest
3 Take
out
the
luggage compartment lining
board and
disconnect the cable
to
the
petrol
gauge
unit
4 Disconnect the
petrol filler tube from the tank
5 Remove the tank
retaining
bolts and disconnect the
rubber fuel outlet and
return
hoses
Installation is
a
reversal of the removal
procedure always
ensure
that the fuel lines
arc
carefully
checked for
signs
of
damage
before
replacing
the tank
FUEL PUMP
Testing
Pressure and
capacity
tests
can
be carried
out
with the
pump installed in the following
manner
Static pressure
test
Disconnect the fuel line at
the carburettor install
an
adaptor
tee
fitting
and suitable pressure gauge
to
the fuel line
between carburettor and fuel pump
Start the
engine
and
run
it
at
varying speeds
The
reading on
the
gauge
should be 0 18 0 24
kg
sq
cm
2 6 34 Ib
sq in
If the pressure is below the
specified
figure then either
one
part
of the
pump
has
worn
excessively
or
general
wear
has occured
to
all the working parts
The faults
may
include
a
ruptured diaphragm
worn
and warped valves
33