1977 DATSUN PICK-UP engine

854
co
in
in
one
minute
or
less

If
no

gasoline
or

only
a

little
flows

from

open
end
of

pipe
with

pump

operated
or
if

pump
does

not
work

perform
the

following
diagnosis

Notes

3
Do
not

connect
battery
in
reverse

polarity
which
if
left
for
a

long

time
would

damage
transitor

circuit
and
disable

pump
Engine
Fuel

b
Do
not
let
fall

pump
as
it

may

damage
electronic

components

c
Do
not

apply
overvoitage
max

l
8Y

Overvoltage
starting

by

quick
charge
or

tage
running

would
deteriorate
or

damage
elec

tronic

components

Fuel

pressure
maximum

0
32

kg
cm
4
6

psi

REMOVAL
AND
INSTALLATION

Flom
fuel
tank

Electric
fuel

pump
is
installed
on

bracket
with
two
bolts
This
bracket
is

located
on
R
H
side
member

adjacent

to
fuel
tank

I
Remove
inlet
hose
from
fuel

pump
Also
remove
outlet
hose
run

ning
to

engine
Receive
fuel

remaining

in
fuel
hose
in
a
suitable
container

2
Disconnect
harness
at

connector

3
Remove
bolts

securing
fuel

pump

to
bracket
and
detach
fuel

pump

4

Installation
is

the
reverse
order
of

removal

9

@

1
Cover

2

Magnet

3
Cover

gasket

4
Filter

5
Gasket

6

Spring
retainer

7
Washer
8
O

ring

9
Inlet
valve

10
Retutn

PIing

11
Plunger

12

Plunger
cylinder

13

Body
To
carburetor

1
Elecuic
fuel

pump

2

Mounting
bracket

3
Fuel
mter

EF72D

Fig
EF
23
Electric
fuel

pump

DISASSEMBLY

Do
not
disassemble
unless

pump
is

faulty

I
Remove

cover
with
wrench
and

take
out
cover
gasket
magnet
and

filter
from

pump
body

2
When

removing
plunger
take
out

spring
retainer
from

plunger
tube

3
Then
take
out
washer
O

ring

inlet
valve
return

spring
and

plunger

from
tube

Note
Do
not
disassemble
electronic

components
If

n

replace

with
new
ones

6

EF721

Fig
EF
24

Exploded
view

of
electric
fuel

pump

EF
12
ASSEMBLY

I

Before

assembly
clean
all

parts

with

gasoline
and

compressed
air

com

pletely

Notes

a
If

gask
t

an
d
fdterare

faulty
r

place

b
Clean

magnet
and
cover
for
fault

c
Take
care
not
to
defonn
thin
tube

d
Assemble

plunger
return

spring

inlet
valve
O

ring
washer
and
set

spring
retainer
in
that
order

e

Assemble
filter

gasket
and
cover

with

f

Tighten
cover
with
wrench
to
the

stopper

If

component
parts
are

dirty
after

disassembly
clean
as
follows

Wash
fIlter
and
strainer
with
clean

gasoline
and
blow
with

compressed

air
When

cleaning
parts
check

fllter
for
fault
If

faulty
replace

Wash

plunger
plunger
cylinder
and

inlet
valve
with
clean

gasoline
and

blow
dust
off

with

compressed
air

2
Check

c
v
m
lI

parts
for
wear

or

damage

If

they
are
found

faulty

replace

them

3

Insert

plunger
assembly
into

plunger
cylinder
of

body
and

apply

electric
current
to
it

Move
the

assembly

up
and
down

If
the

assembly
does
not
move
it

shows

that
the
electric

uuit
is

faulty

and
it
must
be

replaced

Engine
Fuel

TROUBLE
DIAGNOSES
AND
CORRECTIONS

Condition

Fuel

pump
fails
to

operate

Fuel

pump
fails
to

discharge
sufficient

flow

Insufficient
fuel

discharge
during

high
speed
travelling

Low
float
level

at

idling

Fuel

pump
is
actuated

more

frequently
than

under
normal
condi

tion

Rattling
noise
Probable
cause

Terminals
or
connections
loose

Rust
on
terminals
or

grounding
metal

Frozen

liquid
in

plunger
or

pump

Clogged
filter

Insufficient
fuel

Air
in

fuel
hose

through
connections

Hose
necked
down
or
bent

Fuel
tank
breather
tube
bent
or
necked

down

Weakened
return

spring

Air
sucked

through
connection
fuel
hose

and
fuel

pump
joint

Fuel
hose
on
suction
side
bent

Clogged
fIlter

Mounting
bolts
loose

EF
13
Corrective
action

Retighten

Clean

Clean

plunger
assembly

Replace
pump
if

plunger
is

stuck
or
seized

Clean

pump
interior
Clean
and

if

necessary

replace
fIlter

Replenish

Apply
a

coating
of
end
sealing

compound
to

connections
and

retighten

Check
and
correct

Check
and
correct

Replace

Apply
a

coating
of
end

sealing
compound
to

connection
and

retighten

Check
and
correct

Clean
or

replace
fIlter

Retighten

Engine
Fuel

CARBURETOR

CONTENTS

DESCRIPTION

EF
14
CHOKE
UNLOADER

EF
23

STRUCTURE
AND

OPERATION
EF
14

ELECTRIC
AUTOMATIC
CHOKE
EF

24

PRIMARY
SYSTEM

EF
15
INTERLOCK
OPENING
OF
PRIMARY
AND

SECONDARY

SYSTEM
EF
16
SECONDARY
THROTTLE
VALVE

EF
24

ANTI
DIESELING

SYSTEM
EF
17
DASH
POT

EF
25

FLOAT

SYSTEM
EF
18
ACCELERATING
PUMP

EF

25

BOOST
CONTROLLED

DECELERATION
ANTI
DIESELING
SOLENOID
VALVE

EF

25

DEVICE

B
C
D
D
EF
1B

B
C

D
D
CIRCUIT
WITH

FUNCTION

ELECTRIC

AUTOMATIC

CHOKE
EF
20
TEST

CONNECTOR

EF
25

DASH
POT
SYSTEM
EF
20

ALTITUDE
COMPENSATOR

ALTITUDE

COMPENSATOR

California
modelsl
EF

29

California

models

EF
20
MAJOR
SERVICE

OPERATION
EF

29

ADJUSTMENT
AND

INSPECTION
EF
21
REMOVAL
EF
29

CARBURETOR
IDLE
RPM
AND
DISASSEMBLY
AND
ASSEMBLY
EF

30

MIXTURE

RATIO

EF
21
CLEANING
AND

INSPECTION
EF
34

FUEL
LEVEL

EF
22
SERVICE
DATA
AND

SPECIFICATIONS
EF

35

FAST

IDLE

EF
22
TROU8LE

DIAGNOSES
AND

VACUUM
BREAK

EF
23
CORRECTIONS
EF

36

DESCRIPTION

The

carburetors
are
of

down
draft

two

barrel

types
which

produce
the

optimum
air
fuel
mixture
under

all

operating
conditions

They
present
several

distinct

features
of

importance
to
the

vehicle

owners

A

summary
of
the

features
is

as

follows

1
A

slow
economizer
to

make
a

smooth

connection
with

acceleration

or
deceleration

during
light
load

run

ning

It

also

assures
stable
low

speed

performance

2

An
idle

limiter
to

reduce
harmful

exhaust
emissions
to

a
minimum
3
A

B
C
D

D

device
for

reducing

hydrocarbon
H
C
emissions

4

An

electric
automatic

choke
to

facilitate
cold

starting
and
to
reduce

exhaust
emissions

5

An
anti

dieseling
solenoid
to

eliminate

dieseling
run

on

6
A

power
valve

or
vacuum
actu

ated
booster
to

ensure

smooth

high

speed
operation

7

The

carburetor

comes

equipped

with
dash

pot
which
ensures

smooth

deceleration

without

engine
stall

under

all

operating
conditions

8

The
hand

operated
altitude

com

pensator
is

installed
in
the
California

models

EF
14
STRUCTURE
AND

OPERATION

These

carburetors
consist
of

a

primary
system
for

normal

running

and
a

secondary

system
for
full
load

running

A

float

system
common
to
both

primary
and

secondary
systems
a
se

condary
switch

over
mechanism

an

accelerating
mechanism
etc
are

also

attached

An

anti

dieseling
solenoid
valve

and

a

power
valve
mechanism
are
also

installed

The
hand

operated
altitude

com

pensator
corrects
air

fuel
mixture

to

an

optimum
ratio

tZrJ

I
Fuel

nipple

2
Fuel
filter

3

Needle

4
Float

S

Primary
main

jet

6
Idle

adjust
screw

7
I
die
hole

8

Primary

bypass
hole

9

Primary
throttle
valve

10

Primary
altitude

compensator

pipe
California
models

11

Secondary
altitude

compensator

pipe
California
models
Engine
Fuel

jli@

I

12
Air
bleed

13
Primary
slow

jet

14

Plug

15

Primary
slow
air

bleed

6

Primary
main
air
bleed

17

Primary
air

vent

pipe

8
Primary
main
nOlzle

Note
Do

not
remove
the

parts
marked
with
an
asterisk

PRIMARY
SYSTEM

Prlmar
main
s
stem

The

primary
main

system
is
a

Stromburg

type
Fuel
flows
as
shown

in

Figure
EF
25

through
the
main

jet

mixting
with
air

which
comes
in

from

the
main

air
bleed
and

passes
through

the

emulsion
tube
and
is

pulled
out

into

the
venturi

through
the
main

nozzle

IdUns
and
slow
s
stem

During
low

engine
speed
as

shown

in

Figure
EF
25

fuel
flows

through

the
slow

jet
located
on
rear

right
side

of
main

nozzle

mixing
with
air

com

ing
from
the
1st
slow
air
bleed

again

mixing
with
air

coming
from
the
2nd

slow
air
bleed
and
then
is

pulled
out
I

III

@

19

Choke
valve

20

Primary
small
venturi

21

High
speed
enricher

air

bleed

22
Richer
nozzle

23
Richer

jet

24

Secondary
air

vent

pipe

into
the

engine
through
the
idle
hole

and

bypass
hole

Adoption
of
the

submerged

type
of

slow

jet
eliminates

such
hesitation
as

occurs
on
sudden
deceleration
of
the

vehicle

Slow
economizer

system
obtains

smooth
deceleration
at

high

speeds

Small

opening
of
the
throttle

valve

at

idling
or

partial
load

creates
a

large

vacuum

pressure
in
the
intake
mani

fld

By
this

vacuum

pressure
fuel
is

measured

through
the
slow

jet
located

behind
the
main

jet
And
air

coming

from
the
1st

slow
air

bleed
is
mixed

with

fuel
in
the

emulsion
hole

This
mixture
is

further
mixed
and

atomized
with
air

coming
from
the

2nd
slow
air

bleed
The
atomized

mixture
is

supplied
to
the

engine
from

EF15
25

Secondary
main
nozzle

26
Secondary
small
enturi

27
D
C
D
D
a

sembly

28

Secondary
throttle
valve

EF722

Fig
EF
25
Sectional
view

of
carburetor

the
idle
hole
and

bypass
hole
via
the

sow

sysem

passage

Accele

atlns
mechanism

The
carburetor
is

equipped
with
the

piston
type
accelerating
mechanism

linked
to
the

throttle
valve
When
the

primary
throttle
valve
shown
in

Figure
EF
26
is
closed
the

piston

goes
up
and

fuel
flows
from
the

float

chamber
through
the
inlet

valve
into

the

space
under
the

piston
When
the

throttle
valve
is

opened
the

piston

goes
down

opening
the
outlet
valve

and
fuel
is
forced

out
through
the

injector

Engine
Fuel

1
L

if

1

Pump
injector

2
Piston

3

Spring

4

Weight

5

Damper
spring

6
Piston
return

spring

7

Inlet
valve

8
Outlet
valve

EF023

Fig
EF
26
Acceleration

mechanism

Power

valve
mechanism

SECONDARY
SYSTEM

The

power
valve

mechanism
so

called
vacuum

piston

type
utilizes

the

vacuum
below
the
throttle
valve

When
the

throttle
valve
is

slightly

opened
during
light
load

running

high

vacuum
is

created
in

the
intake
mani

fold
This

vacuum

pulls
the

vacuum

piston
upward

against
the

spring

leaving
the

power
valve
closed
When

the
vacuum
below
the
throttle

valve
is

lowered

during
full
load
or

accelerat

ing

running
the

spring

pushes
the

vacuum

piston
downward

opening
the

power
valve
to
furnish

fuel
Secondary
main

lIYlltem

pulled
out

through
the
main

nozzle

into
the
small
venturi

Due
to
the

double
venturi

of
the

secondary
system
the

higher

velocity

air

current

passing
through
the
main

nozzle

promotes
the
fuel
atomization

The
structure
is

almost
the

same
as

the

primary
side
The

secondary
main

system
is

a

Stromburg
type

Fuel
air
mixture

produced
by
the

functions
of
the
main

jet
main
air

bleed

and
emulsion
tube
in

the
same

manner
as
in

the

primary
system
is

11
1

I

1

1

Primary
vacuum

port

2

Secondary
vacuum

port

3

Diaphragm
chamber

cover

of

Diaphragm

spring

S

Diaphragm

6

Secondary
throttle

valve

7

Primary
theo
nle

valve
lWll
I

1
11

l
v
1

Vacuum

piston

2

Power

valve

ET02
a

EF
512

Fig
EF
27
Sectional

view

of

po
r

valve

Fig
EF
28
Full
throttle
al

high
peed

EF

16

Step
system

The

construction
of
this

system

may

correspond
to
the

idling
and
slow

system
of

the

primary
system

Tlris

system
aims

at
the

proper

filling
up
of
the

gap
when

fuel

supply

is
transferred
from
the

primary
system

to
the

secondary
one
The

step
port
is

located
near
the

secondary
throttle

valve

edge
in
its

fully
closed

state

Secondary
switchover
mechanism

The

secondary
throttle
valve
is

linked
to
the

diaphragm
which
is

actuated

by
the
vacuum

created
in
the

venturi
A

vacuum

jet
is

provided
at

each
of
the

primary
and

secondary

venturies
and
the

composite
vacuum

of
these

jets
actuates
the

diaphragm

As
the

linkage
causes
the

secondary

throttle
valve
to
close
until
the

prima

ry
throttle
valve

opening
reaches

ap

proximately
500
fuel

consumption

during
normal

operation
is

not
exces

sive

During
high
speed
running
as

shown
in

Figure
EF
28
as
the

vacuum

at
the
venturi
is
increased
the
dia

phragm
is

pulled
against
the

diaphragm

spring
force
and
then

secondary
throt

tie
valve
is

opened

The
other

side

during
low

speed

running
as
the

primary
throttle
valve

opening
does
not
reach
500
the

secondary
throttle
valve
is

locked
to

close

completely
by
the

locking
arm

which
is
interlocked
with

primary

throttle
arm

by
linkage

When
the

primary
throttle
valve

opening
reaches
wider

position
than

500
the

secondary
throttle
valve
is

ready
to

open
because
the

locking

arm
revolves
and
leaves
from
the

se

condary
throttle
arm
Engine
Fuel

HI
h

speed
circuit

The
high

speed
circuit

improves

high
engine
output
performance

during
high

speed
driving

This
circuit

operates
only
when

driving
at

high
speed
It
consists
of
a
richer

jet
high
speed
enricher
air

bleed
and
richer
nozzle
When
the

velocity
of
suction
air

flowing

through

the

carburetor
secondary
bore
in

creases
additional
fuel
is
drawn

out
of

the

richer
nozzle

@
2

EF234

Secondary
I

Richer

jet

2

High
speed
enricher

air
bleed

3
Richer
nozzle
Primary

Fig
EF
29

High
speed
circuit

ANTI
DIESELlNG
SYSTEM

is

brought
into

operation
shutting
off

the

supply
of
fuel
to
the
slow
circuit

The

following
figure
shows
a

see

tiorial
view

of
this
control
The
carburetor
is

equipped
with
an

anti

dieseling
solenoid
valve

As
the

ignition
switch
is
turned
off
the
valve

EF230

@

l
CD

1

1
g

@eI

1
Anti
dieseling

solenoid
va1

2

Ignition
switch

3

Battery

Fig
EF
30
Schematic
drawing
of
anti

dieseling
sydtm

EF
17

FLOAT
SYSTEM

There
IS

only
one

float
chamber

while
two
l

arburetor

systems
primary

Jnd

st
l

ondary
are

provided

Fuel
fed
from
the
fuel

pump
flows

through
the
filler
and
needle

valve
into

the
flo
t
chamber
A

constant
fuel

level

is
maintained

by
the
float
and

needle
valve

Because
of

the
inner
air

vent

type

of

the
float
chamber
ventilation
the

fuel

consumption
will
not

be
in

fluenced

by
some
dirt
accumulated
in

the
air

deaner

The
needle
valve

includes

special

hard
steel
ball

and
will
not

wear
for
all

its

considerably

long
use
Besides
the

inserrion

of
a

spring
wiU

prevent
the

flooding
at

rough
road

running

BOOST

CONTROLLED

DECELERATION
DEVICE

B
C
D
D

A

Boost
Controlled
Deceleration

Device
B

C
D

D
serves
to

reduce
the

hydrocarbons

He
emitted
from
en

gine
during
coasting

The

high
manifold
vacuum

during

coasting

prevents
the
mixture

from

complete
combustion

because
of
the

reduced
amount
of
mixture

per
cyl

inder

per
rotation

of

engine
with
the

result
that

a

large
amount
of

hydrocar

bons
is

emitted
into
tile

atmosphere

The
B

C
D
D
has
been

designed
to

correct

this

problem

It

opern
tes

as
follows

when
the

manifold

vacuum
exceeds
a

pre
Engine
Fuel

determined

value
the

B
C
D
D
intro

duces

an
additional
mixture

of

opti

mum
mixture
ratio
and

quantity
into

the

manifold

by

opening
a

separate

mixture

passage
in
the

carburetor

Complete
combustion

of
fuel
is
assist

ed

by
this
additional
mixture

and
the

amount

of
H
C

contained
in

exhaust

gases
is

dramatically
reduced

During
the

transition

period
from

coasting
to

idling
the
transmission

produces
a

signal
which
turns
on
the

vacuum
control

solenoid
valve
As
this

takes

place
the
valve
is

lifted
off
its

seat

opening
the

vacuum
chamber
to

the

atmosphere
The
mixture

control

valve
is
then

closed

returning
the

engine
to
the

predetermined
idling

speed

On
manual

transmission
models

this

system
consists

of
B
C
D
D

vacuo

urn
control

solenoid
valve

speed
de

tecting
switch
and

amplifier

On
automatic

transmission

models

it
consists

of
B
C
D
D

vacuum
con

trol

solenoid
valve

and

inhibitor

switch

B
C
D
D

operation

Diaphragm
I

Qj
monitors
the

mani

fold

vacuum
and

when
the

vacuum

exceeds
a

pre
fetermined
value
acts
so

as

to

open
the

vacuum
control
valve

@
This
causes

the
manifold

vacu
urn

to
be

introduced
into
the

second

vacuum
chamber
and

actuates
dia

phragm
ll@

When

diaphrngm
II

operates
the

mixture

control
valve

@
opens
the

passage
and
introduces
the
additional

mixture
into

the
manifold

EF

18
The
amount
of

the
mixture

is
con

trolled

by
the

servo
action

of
the

mixture
control

valve

CID
and

vacuum

control

valve

@
so

that

the
manifold

vacuum

may
be

kept
at
the

pre

determined

value

The
amount

of
mixture

depends

mainly

upon
the

coasting
air
bleed

II@
while
the
mixture
ratio

is
deter

mined

by
the

coasting
jet

@
and

coasting
air
bleed

@
See

Figure

EF
31

Vacuum

control
solenoid

valve

operation

Manual

transmission
models

The

vacuum
control

solenoid
valve

is

con
troDed

by
a

speed

detecting

switch
that
is

actuated

by
the

speed

ometer
needle

As
the
vehicle

speed
falls

below
10

MPH
this
switch
is
activated

pro

ducing
a

signal
This

signal
actuates
the

amplifier
to

open
the
vacuum
control

solenoid
valve

Automatic

transmission
models

When
the

shift
lever
is
in
N

or

P

position
the
inhibitor
switch

mounted
on
the
transmission

turns
on

to

open
the
vacuum

control
solenoid

valve

I
Air

jet

2

Diaphragm
II

3
Mixture
control
valve

4

Coasting
air

bleed
II

5
Mixture
air

passage

6

Secondary
baHel

7
Intake
manifold

8
Boost

passage

9
Vacuum
control
solenoid

valve

10
Vacuum
control
valve

II

Diaphragm
I
Engine
Fuel

12

Secondary
main

jet

13

Coasting
jet

14

Coasting
air
bleed
I

15
Inhibitor
switch
N

P

ON
for
automatic

transmission

16

Amplifier

1
7

Speed
de

tecting
swi
tch
below

10
M
P
H
ON

for
manual

transmission

1

W
j

I

t

i
J

l

J
18

Ignition
switch
CID

1
1

fI3
6

@
I

r
101

@
i

r

@

JJ

Note
Broken
line

applies
only
to
Automatic
Transmission

I

Ignition
switch

2

Amplifier

3

Speed
detecting
switch
below

10
M
P

H
ON
for
manual

transmission

4
Inhibitor
switch
N
p

ON
for
automatic

transmission

5
Solenoid
valve

6
Vacuum
control
valve

7
Altitude

corrector

LlJ

I

I

l

f

L8
J

l
EF231

Fig
EF
31
Schematic

drawing
of
B
C
D
D
Non

California
models

1

J
ru

I

r

lJ

i7

I
To
intake

manifold

To
air

cleaner

E
F235

Note
Broken
line

applies
only
to
Automatic
Transmission

Fig
EF
32
Schematic
drawing
of
RC
D
D

California
models

EF
19