1977 DATSUN PICK-UP ignition

Condition

NOISY

ENGINE

Car

knocking

Mechanical

knocking

Crankshaft

bearing

Imocking

Connecting
rod

bearing
knocking

Piston
and

cylinder

noise

Piston

pin
noise

Water

pump
noise

Air

pump
noise

Others
Engine
Tune

up

Probable
cause

Overloaded

engine

Carbon

knocking

Timing
knocking

Fuel

knocking

Preignition
misusing
of

spark
plug

This

strong
dull
noise
increases
when

engine

is

accelerated
To
locate
the

place
cause
a

misfire

on
each

cylinder
If
the
noise

stops

by
the
misfire
this

cylinder
generates
the

noise

This
is
a
little

higher
pitched
noise
than
the

crankshaft

Imocking
and
also
increases

when

engine
is
accelerated
Cause
a
misfire

on
each

cylinder
and
if
the
noise
deminishes

almost

completely
this
crankshaft

bearing

generates
the
noise

When

you
hear
an

overlapping
metalic
noise

which
increases
its

magnitude
with
the

revolution
of

engine
and
which
decreases
as

engine
is
warmed

up
this
noise
is
caused

by

piston
and
cylinder
To
locate
the

place

cause
a
misfire
on
each

cylinder

This
noise
is

heared
at
each

highest
and

lowest
dead
end
of

piston
To
locate

the

place
cause
a

misfire
on
each

cylinder

This
noise

may
be
caused

by
worn
or

damaged
earings
or
by
the
uneven
surface

of
sliding

parts

Damaged
air

pump

An
improper
adjustment
of
valve
clearance

Noise
of

timing
chain

An
excessive
end

play
on
crankshaft

Noisy
E
F
E

valve
shaft

Wear
on
clutch

pilot
bushing

Note
This
noise
will
be
heared
when

clutch
is

disengaged

ET31
Corrective
action

Use

right
gear
in
driving

Disassemble

cylinder
head
and

remove

carbon

Adjust
ignition
timing

Use

specified
octane
fuel

Use

specified
spark
plug

This
is

caused

by
worn
or

damaged
bearings

or
unevenly
worn
crankshaft
Renew

bearings
and

adjust
or

change
crankshaft

Check
lubrication

system

Same
as
the
case
of
crankshaft

bearings

This

may
cause
an
abnormal

wearing
of

cylinder
and
lower

compression
which
in

turn
will
cause
a
lower
out

put
power
and

excessive

consumption
of
oil

Overhaul

engine

This

may
cause
a
wear
on

piston
pin
or

piston
pin
hole

Renew

piston
and

piston

pin
assembly

Replace
water

pump
with
a
new
one

Repair
or

replace

Adjust

Adjust
the
tension
of
chain

Disassemble

engine
and
renew
main
bearing

Repair

Renew
bush

and

adjust
drive
shaft

Condition

ABNORMAL

COMBUSTION

backfue
afterflre

run
on
etc

Improper

ignition
timing

Fuel

system
out
of

order

Faulty
cylinder
head
etc

Others

EXCESSIVE
OIL

CONSUMPTION

Oilloak

Excessi
lo
oil

consumption

Others
Engine
Tune

up

probable
cause

Improper
ignition
timing

Improper
heat

range
of

spark
plugs

Damaged
carburetor

or
manifold

gasket

backfue
afterfire

Clol
l
ed
carburetor

jet

Improper
function
of

the
float

Uneven

idling
Run
on

Improperly
adjusted
B

C
D
D

set

pressure

Malfunction
of
anti

dieseling
solenoid
valve

Malfunction
of
auio
choke

Improperly
adjusted
valve
clearance

Excess
carbon
in

combustion
chamber

Damaged
valve

spring
backfire
afterflre

Malfunction
of

A
T
C

air
cleaner

Inoperative
ariti
backfue
valve

Loose
oil
drain

plug

Loose

or
damaged
oil

pan
gasket

Loose
or

damaged
chain
cover

gasket

Worn
oil
seal
in
front
and
rear
of
crankshaft

Loose
or

damaged
locker
cover

gasket

Improper
tightening
of
oil
filter

Loose
or

damaged
oil

pressure
switch

Cylinder
and

pioton
wear

Improper
location
of

piston
ring

gap
or

reversely
assembled

piston
ring

Damage
piston
rings

Worn

piston
ring
groove
and

ring

Fatigue
of
valve
oil
seal

lip

Worn
valve

stem

Inadequate
quality
of

engine
oil

Engine
overheat

ET32
Corrective
action

Adjust
ignition
timing

Use

specified
spark
plugs

Replace
them
with
new

parts

Disassemble
carburetor
and
check
it

Adjust
the
level
and
check
needle
valve

Adjust

Adjust

Check
or

replace

Adjust

Adjust

Remove
head
and

get
rid
of
carbon

Replace
it
with
a
new
one

Check
for
loose
vacuum
hoses

Replace
if

necessary

Replape

Tighten
it

Renew

gasket
or

tighten
it

Renew

gasket
or

tighten
it

Renew
oil
seal

Renew

gasket
or

tighten
it
but
not
too

much

Renew

gasket
and

tighten
it
with
the

proper

torque

Renew
oil

pressure
switch
or

tighten
it

Overhaul

cylinder
and
renew

piston

Remoun
t

piston
rings

Renew

rings

Repair
or
renew

piston
and

cylinder

Renew

piston
and

piston
ring

Replace
seal

lip
with
a

new
one

Renew
valve
or

guide

Use
the

designated
oil

Previously
mentioned

Condition

POOR
FUEL
ECONOMY

Se
the

xplanation

of
the
pow
r

dec

Oth
n

PROBLEM
IN

OTHER

FUNCTIONS

D
cr
d

oil

p
ssure

Excessive
wear
on
the

sliding

parts

Scuffing
of

sliding

parts

Floor

temperature
too

high
California

only
Engine
Tune

up

Probable
cause

Exceeding
idling
revolution

Inoperative
acceleration
recovery

Fuel

leakage

Malfunction
of
B

C
D
D

Malfunction
of
A
r
C
air

cleaner

Inadequate
oil

quality

Overheat

Worn

oil

pump
regulator
valve

Functional
deterioration
of
oil

pump

Blocked
oil
f1lter

Increased
clearance
in
various

sliding
parts

Blocked
oil
strainer

Inoperative
oil

gauge
pressure
switch

Oil

pressure
decreases

Improper

quality
or
contamination
of

oil

Damaged
air
cleaner

Overheat
or
overcoal

Improper
fuel
mixture

Decrease
of
oil

pressure

Insufficient
clearances

Overhea
t

Improper
fuel

mixture

Problem
in

fuel

system
Refer
to

Inspec

tion
of
Fuel

System

Problem
in

ignition
system
Refer
to
In

spection
of

Ignition
System

ET33
Corrective
action

Adjust
it

to
the

designated
rpm

Adjust
it

Repair
or

tighten
the
connection
of

fuel

pipes

Adjust

Check
and

replace

Use
the

designated
oil

Previously
mentioned

Disassemble
oil

pump
and

repair
or
renew
it

Repair
or

replace
it

with
a

new
one

Renew
it

Disassemble
and

replace
the
worn

parts
with

new
ones

Oeanit

Replace
it
with
a
new
one

Previousiy
mentioned

Exchange
the
oil
with

proper
one
and

change
element

Change
elemen
t

Previously
mentioned

Check
the
fuel

system

Previously
mentioned

Readjust
to
the

designated
clearances

Previously
mentioned

Check
the
fuel

system

Check
and

repair

Check
and

repair

Engine
Mechanical

GENERAL
DESCRIPTION

MODEL

L20B
ENGINE

CYLINDER
BLOCK

CRANKSHAFT

PISTON
AND
CONNECTING
ROD

CYLINDER
HEAD
CONTENTS

EM
2

EM
3

EM
3

EM
3

EM
3
CAMSHAFT

VALVE
MECHANISM

CAMSHAFT
DRIVE

MANIFOLDS

out
smooth

dependable

power

The

cylinder
block
is
cast
as
a

single

unit

and

featllres
deep
skirting
This

engine
is

equipped
with
a

single
2

barrel
downdraft
carburetor
that
in

corporates
a

special
device
to
control

emissions
MODEL
L20B

ENGINE

The
L20B

engine
features
O
H
C

valves

wedge
shaped
combustion

chamber
aluminum
head
and
a

fully

balanced
5

bearing
crankshaft
to
turn

Main

specifications

Oisplacemen
t
cc

cu
in

Bore
x
stroke

mm
in

Compression
ratio

Ignition

timing

Degree
B

T
O
C

rpm
MIT

AlT

MIT
Manual
Transmission
EM535

Fig
EM
Cross
sectional
view

L20B

1

952
1191

85

X
86

3
35
x
3
39

8
5

12
750

Non
California

model

10
750

California

model

12
650
in
0
position

AIT
Automatic
Transmission

EM

2
EM
3

EM
3

EM
3

EM
3

CYLINDER
BLOCK

The

cylinder
block
a
mono
block

special

casting
structure

employs
a

five
bearing

support

system
for

quiet

ness

and

higher
durability

The

cylinder
bores
are
surrounded

by
cooling

jackets
and
machined
di

rectly
in
the
block
The
oil

ways
in
the

block

are
arranged
so
that
the

full
flow

oil
filter
is

directly
attached
to
the

right
hand
side
of
the
block

EM536

Fig
EM

2
Cylinder
block

CRANKSHAFT

The
crankshaft
is

a

special
steel

forging
Fully
balanced
it
turns
out

smooth

dependable
power
at

high

speed

The
L20B

engine
uses

eight
balance

weights

Main

bearings
are
lubricated

by
oil

pumped
through
the
main
oil

gallery

and
the
oil
holes
which
run
in

parallel

with

cylinder
bores
There

are

oilways

drilled
in

the
crankshaft
for
the
lubri

cating
oil
The
center
main

bearing
is

equipped
with
thrust
washers

to
take

up
end

thrust
of
the
crankshaft

Condition

Loss

of
water

Poor
circulation

Corrosion

Overheating

Overcooling
Cooling
System

TROUBLE
DIAGNOSES
AND
CORRECTIONS

Probable
cause

Damaged
radiator
seams

Leaks
at
heater
connections
or

plugs

Leak
at

water

temperature
gauge

Loose

joints

Damaged
cylinder
head

gasket

Cracked

cylinder
block

Cracked

cylinder
head

Loose

cylinder
head

bolts

Restriction
in

system

Insufficient
coolant

Inoperative
water

pump

Loose

fan
belt

Inoperative
thermostat

Excessive

impurity
in

water

Infrequent
flushing
and

draining
of

system

Inoperative
thermostat

Radiator
fin
choked
with
mud
chaff
etc

Incorrect

ignition
and
valve

timing

Dirty
oil
and

sludge
in

engine

Inoperative
water

pump

Loose
fan
belt

Restricted
radiator

Inaccurate

temperature
gauge

Impurity
in

water

Inoperative
thermostat

Inaccurate

temperature
gauge

CO
7
Corrective
action

Repair

Repair

Tigh
ten

Tighten

Replace

Check

engine
oil
for
contamination
and
refill

as

necessary

Replace

Check

engine
oil
in
crankcase
for

mixing

with

water

by
pulling
oil
level

gauge

Replace

Tighten

Check
hoses

for

crimps
and

clear
the

system

of
rust
and

sludge
by
flushing
radiator

Replenish

Replace

Adjust

Replace

Use
soft
clean
water
Rain

water
is
satis

factory

Cooling

system
should
be

drained
and

flushed

periodically
Permanent
anti
freeze

Ethylene
glycol
base
can
be

used

through

out
the

seasons
of
the

year
and

change

periodically
at
intervals
recommended

Replace

Clean
out

air

passage
thoroughly
by
using
air

pressure
from

engine
side
of
radiator

Adjust

Refill

Replace

Adjust

Flush
radiator

Replace

Use
soft
clean
water

Replace

Replace

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

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

Notes

a

The
idle

rpm
and
CO

vary
accord

ing
to
the
altitude
Therefore

they

should
be

properly
adjusted
when

the

position
of
the
H
L
lever
is

changed

EF729

ADJUSTMENT

AND
INSPECTION

CARBURETOR
IDLE
R
P
M

AND
MIXTURE
RATIO

Cautions

3
On

automatic
transmission

equi

ped
models
check
should
be

per

formed
in

the
0

position

Be
sure
to

engage

parking
brake
and

to
lock
both
front
and

rear
wheels

with
wheel
chocks

b

Keep
your
foot
down
on
the
brake

pedal
while

depressing
the
accelera

tor

pedal
Otherwise
vehicle

surges

forward

dangerously

Notes

a
00
not

attempt
to
screw
the
idle

adjusting
screw
down

completely

Ooing
so
could
cause

damage
to

tip

which
in
turn
will
tend
to
cause

malfunctio11ll

b
If
idle
limiter

cap
obstructs

proper

adjustment
remove
it

To
install
idle
limiter

cap
refer
to

Idle
Limiter

Cap

c
After
idle

adjustment
has
been

made
shift
the
lever
to
the
N

or

P

position
for
automatic
trans

mission

d
When

measuring
CO

percentage
in
Engine
Fuel

b
Counties
1

219
m
4
000
ft
or

more
above
sea
level
have
been

designated
by
law
as

High
Altitude

Counties
For

further
details
refer

to
1977
OATSUN
PICK
UP
Service

Bulletin
Pub
No
257

0

I
Air
cleaner

rID
mOl

If
Low
altitude

Ll

n
n

L
n

Fig
EF
34

sert

probe
into
tail

pipe
more
than

40
em

15
7
in

CO
Idle

adjustment
with

CO
meter

Idle
mixture

adjustment
requires

the
use
of
a

CO
meter

especially
for

California
models
When

preparing
to

adjust
idle
mixture
it
is

essential
to

have

the
meter

thoroughly
warmed

up

and

calibrated

I

Check
carburetor

pipes
for

proper

connection

2
Warm

up

engine
until
water

tem

perature
indicator

points
to
the
middle

of

gauge
The

procedure
to
warm

up

engine
is
not

specifically
recom

mended
Either

driving
vehicle
or

oper

ating
engine
at

no
load
will

be

good

3
Make
sure
that
water

tempera

ture
indicator

points
to
the
middle

Further

keep

engine
running
at
about

2
000

rpm
for

about
5

minutes
with

out

applying
load
to

engine
in

order
to

stabilize

engine
condition

Engine

hood
should
be

open

4
Run

engine
for
about

10
minutes

at

idling
speed
Ouring
this
10

minutes

proceed
as
described
in

steps

5

to
9
below

5
Remove
air

hose
between
3

way

connector
5

way
connector
for
Cali

fornia
models
and
air

check
valve
as

EF
21
shown
in

Figure
EF
35

Plug
the
dis

connected
hose

to

prevent
dust

from

entering

0

o

EF259

Fig
EF
35
Disconnecting
air
hose

from
air
check
valve

6
Race

engine
I
500

to
2
000

rpm

two
or
three
times

under
no
load
then

run

engine
for
one
minute
at

idling

speed

7

Adjust
throttle

adjusting
screw

until

engine
is

at

specified
speed

Engine
speed

Manual
transmission

750

rpm

Automatic
transmission

in
0

position

650

rpm

8
Check

ignition
timing
If
neces

sary
adjust
it
to

specifications

This

operation
need
not
be
carried

out
at
1

600
Ian
1

000
miles
service

Ignition
timing

Manual
transmission

120
750
rpm
Non
California

100
750

rpm
California

Automatic
transmission

in
0

position

120

650

rpm

9
At

about
10
minutes

after

engine

is
run

at

idling
speed
adjust
idle

adjusting
screw
so

that
CO

percentage

is
at

specified
level

CO

percentage

Manual
transmission

2
t
l

at
750

rpm

Automatic

transmission

in
0

position

2
t
I
at
650

rpm

10

Repeat

procedures
as
described

in

steps
6

7
and
9
above

so
that
CO

percentage
is
at

specified
level
Check

ing
idle
CO
in

step
9
can

be
carried
out

right
after

step
7

II
Race

engine

1
500
to
2

000