Servicing Gasoline Fuel System

OPERATION SHEET LO3–2

LO3: PERFORM CARBURETOR ADJUSTMENT

INSPECTION & ADJUSTMENT OF CARBURETOR

PURPOSE : To master the procedure for adjusting the idle speed and idle
mixture

PREPARATION : SST 09243-00020 Idle adjusting screw wrench
• Ohmmeter (circuit tester, multimeter)
• Tachometer
• CO meter … Europe and General Countries only

APPLICABLE ENGINE : TOYOTA 4A - F

INITIAL CONDITIONS OF CARBURETOR ADJUSTMENT

1. All accessories switched off
2. Ignition timing set correctly
3. Transmission in “N” range (A/T vehicles

or neutral (M/T vehicles)
4. Engine warmed up to normal operating

temperature
5. Float level indicating correct fuel level in

sight glass
6. Choke valve able to open fully

7. Tachometer connected

Remove the rubber cap and connect the
tachometer positive (+) terminal to the
service connector of the IIA.

CHECKING IDLE SPEED:

Idle speeds: Europe and General Countries
•

AT, w/PS 900 rpm

Others 800 rpm

• USA and Canada
AT 750 rpm
MT 650 rpm

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ADJUSTMENT OF IDLE MIXTURE WITH CO METER (Europe and General Countries)

CAUTION:

• Always use a CO meter when adjusting the idle mixture. It is not necessary to adjust
with the idle mixture adjusting screw inmost vehicles if the engine is in good condition.

• Use the alternative method only if a CO meter is not available and it is absolutely
necessary to adjust with the idle mixture adjusting screw.

1. DISCONNECT AIR SUCTION (AS)
VACUUM HOSE AND PLUG HOSE
END (Germany, w/TWC [Three-Way
Catalytic converter])

Note: This will shut off the AS system.

2. ADJUST IDLE SPEED AND IDLE
MIXTURE

Using a CO meter to measure the CO
concentration in the exhaust, turn the
idle speed and idle mixture adjusting
screws to obtain the specified
concentration value at idle speed.

SST 09243-00020 (Europe only)
NOTE: Make the adjustment with the
cooling fan off.

3. CHECK CO CONCENTRATION

(a) Check that the CO meter is

properly calibrated.

(b) Race the engine for 30 – 60

seconds at about 2,000 rpm

before measuring the

concentration.

(c) Wait 1 – 3 minutes after racing

the engine to allow the

concentration to stabilize.

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(d) Insert a test probe at least 40 cm
(1.3 ft) into the tailpipe, and
measure the concentration within
a few seconds.
Idle CO concentration:
Germany (w/TWC) 0 – 0.5%
Others 1.0 – 20%
• If the CO concentration is
within specification, this
adjustment is complete.
• If the CO concentration
exceeds specification, or if
the engine begins idling
roughly again, repeat the
above adjustment.

ADJUSTMENT OF IDLE MIXTURE WITHOUT CO METER (Europe and General Countries)

1. DISCONNECT AIR SUCTION (AS)
VACUUM HOSE AND PLUG HOSE END
(Germany [w/TWC])

NOTE: This will shut off the AS system.

2. ADJUST IDLE SPEED AND IDLE MIXTURE
The following procedure is the lean drop method
for setting idle speed and mixture:

(a) Set to the maximum speed by turning the

idle mixture adjusting screw.

(b) Set to the idle mixture speed by turning the

idle speed adjusting screw.

Idle mixture speed: A/T, w/PS 960 rpm

Others 860 rpm

(c) Before moving to the next step, continue

adjustments (a) and (b) until the maximum

speed will not rise any further no matter how

much the idle mixture adjusting screw is

adjusted.

(d) Set to the idle speed by screwing in the idle

mixture adjusting screw.

Idle speed: A/T, w/PS 900 rpm

Other 800 rpm

NOTE: Make the adjustment with the cooling fan off.

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ADJUSTMENT OF IDLE MIXTURE (USA and Canada)

NOTE:
• To conform with USA and Canada regulations, the idle mixture adjusting screw is adjusted

and plugged with a steel plug by the manufacturer. Normally, this plug should not be
removed.
• When troubleshooting rough idle, check all other possible causes before attempting to
adjust the idle mixture.
Only if no other factors are found to be at fault should the idle mixture be adjusted. When
doing so, remove the plug and follow the procedure described below.

1. REMOVE CARBURETOR

(a) Before disconnecting the vacuum
hoses, attach tags to identify now they
should be re-connected.

(b) Remove the carburetor from the engine.
(c) After removing the carburetor, cover the

in-take manifold with a clean rag.

2. REMOVE MIXTURE ADJUSTING SCREW
PLUG (MAS PLUG)

(a) Plug each carburetor vacuum port to
prevent entry of steel particles when
drilling.

(b) Mark the center of the plug with a punch.

(c) Drill a 6.5 mm φ (0.256 in φ) hole in the
center of the plug.

CAUTION:
As there is only 1 mm (0.04 in.) of clearance
between the plug and screw, drill carefully
and slowly to avoid drilling onto the screw.

(d) Through the hole in the plug, fully screw-
in the mixture adjusting screw with a
screw driver.

NOTE: Be careful not to damage the screw
tip by tightening the screw too tight.

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(e) Use a 7.5 mmφ (0.295 in. φ) drill to
remove the plug.

3. INSPECT MIXTURE ADJUSTING SCREW
(a) Blow off any steel particles with
compressed air.
(b) Remove the screw and inspect it. If the
drill has gnawed into the screw top or if
the tapered portion is damaged, replace
the screw.

4. REINSTALL MIXTURE ADJUSTING
SCREW
Fully screw in the idle mixture adjusting
screw and then unscrew it
counterclockwise the specified amount

Screw revolutions: 3 – ¼ revolutions
NOTE: Be careful not to damage the screw
tip by tightening the screw too tight.

5. REINSTALL CARBURETOR
(a) Reinstall the carburetor on the engine.
(b) Reconnect the vacuum hoses to the
proper locations. Refer to the Vacuum
Hose Information label under the hood.

6. REINSTALL AIR CLEANER

7. ADJUST IDLE SPEED AND IDLE
MIXTURE
(a) Initial steps:
• Air cleaner installed
• Coolant at normal operating
temperature
• Choke fully open
• All accessories switched off
• All vacuum lines connected
• Ignition timing set correctly
• Transmission in “N” range or neutral

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• Float lever indicating correct fuel level in sight glass
• Front wheels in straight-ahead position (PS-equipped vehicles only)
(b) Start the engine.
(c) Set to the maximum speed by turning the idle mixture adjusting screw.
NOTE: Insert a small screwdriver between the EGR valve and the EGR vacuum modulator
bracket.

(d) Set to the idle mixture speed by turning
the idle speed adjusting screw.

Idle mixture speed: 700 rpm

(e) Before moving to the next step, continue
the adjustments (c) and (d) until
maximum speed will not rise any further
no matter how much the idle mixture
adjusting screw is adjusted.

(f) Set to 650 rpm by screwing in the idle
mixture adjusting screw.

This is lean drop method for setting idle
speed and mixture.

(g) Set to the idle speed by screwing in the
idle speed adjusting screw.

Idle speed: 650 rpm (M/T)
750 RPM (A/T)

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8. PLUG IDLE MIXTURE ADJUSTING
SCREW
(a) Remove the air cleaner and EGR
vacuum modulator bracket.
(b) With the tapered end inward, tap in the
plug until it is even with the carburetor
surface.

ADJUSTMENT OF FAST IDLE SPEED

1. PLUG AS, ASV AND HIC HOSES (USA
and Canada)

Plug the AS hose to prevent leakage of
exhaust gas, and the ASV hose (California
only) and HIC hose to prevent rough idling.

2. DISCONNECT VACUUM HOSE FROM
TVSV M PORT

Disconnect the vacuum hose from the
TVSV M port and plug the M port. This will
shut off the choke opener and EGR
systems. (USA, Canada, and Germany
[w/TWC]).

3. SET FAST IDLE CAM

While holding the throttle valve slightly
open, pull up the fast idle cam and h old it
closed as you release the throttle valve.
NOTE: Check that the fast idle cam is set
as in the figure. Start the engine, but do not
depress the accelerator pedal.

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4. ADJUST FAST IDLE SPEED

Adjust the fast idle speed by turning the
fast idle adjusting screw.
Fast Idle speed: 3,000 rpm
NOTE: Make adjustment with the cooling
fan off and transmission in “N” range (A/T).

ADJUSTMENT OF THROTTLE POSITIONER
(TP) SET SPEED

1. DISCONNECT VACUUM HOSE FROM
THROTTLE POSITIONER

2. ADJUST TP SET SPEED

TP Set Speed:

Europe and General countries 1,400

rpm

USA and Canada 900

rpm

NOTE: Check with the engine cooling fan

off and the transmission in the “N” range

(A/T)

3. RECONNECT VACUUM HOSE TO
THROTTLE POSITIONER

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SELF-CHECK LO3–2

• Enumerate the initial conditions of carburetor adjustment.

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ANSWER KEY LO3–2

Initial conditions of carburetor adjustment

1. All accessories switched off.
2. Ignition timing set correctly.
3. Transmission in “N” range (A/T vehicles) or neutral (M/T vehicles)
4. Engine warmed up to normal operating temperature.
5. Float level indicating correct fuel level in sight glass.
6. Choke valve able to open fully.
7. Tachometer connected.

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QUALIFICATION : Automotive Service Technicians

UNIT OF COMPETENCY : Service Engine Mechanical System

MODULE TITLE : Servicing Gasoline Fuel System

LEARNING OUTCOME 4 : Overhaul Carburetor

ASSESMENT CRITERIA:

1. Technical data accessed and interpreted from manufacturer’s specification.

2. Tools and equipment used in accordance with industry standard.

3. Carburetor overhauled in accordance with the required steps and procedure.

RESOURCES:

1. Auto Mechanics, theory and service by: deKryger. Kobacik Bono

2. Corolla, service and repair manual

3. Lancer, service and repair manual by: Gregory’s Scientific Publication

4. Toyota Training Manual by: Toyota

5. VHS/CD

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LO4 – Overhaul Carburetor SPECIAL INSTRUCTIONS

LEARNING ACTIVITIES
• Observe safety precautions
• Wear personal protective equipment
• Always perform 5’s

In the training workshop, using different types • View VHS / CD
of engine and guided by instructional materials and • Perform Operation Sheet LO4-1
service manuals, overhaul carburetor using tools • After viewing VHS/ CD and
and equipment according to industry standards.
performing the Operation Sheet No.
LO4-1, answer Self-Check LO4-1
and compare your answers with the
answer key provided.

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OPERATION SHEET LO4–1

LO4: OVERHAUL CARBURETOR

OVERHAULING CARBURETOR

PURPOSE : To master the procedure for disassembly, assembly, checking and
adjustment of the carburetor.

PREPARATION : SST 09240-00014 Carburetor adjusting gauge set
09240-00020 Wire gauge set
09860-11011 Carburetor drive set

APPLICABLE ƒ Ohmmeter (circuit tester, multi tester)
ENGINE ƒ Carburetor overhaul kit
ƒ Gasket kit

: TOYOTA 4A-F

COMPONENTS

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MAIN POINTS IN CARBURETOR OVERHAUL

Disassembly of Carburetor

NOTE: The following instructions are
organized so that you will work on only one
component group at a time. This will help
avoid confusion between similar-looking parts
from different sub-assemblies being on your
workbench at the same time.

(a) To facilitate reassembly, arrange parts in
order.

(b) Be careful not to mix up or lose balls, clips
or springs.

(c) Use the carburetor driver set (SST). SST
09860-11011

Disassembly of Air Horn

REMOVE FOLLOWING PARTS
• Air horn assembly
• Float and needle valve
• Piston retainer (1), power piston
(2), and pump plunger (3)
• Automatic choke

Disassembly of Carburetor Body

REMOVE FOLLOWING PARTS
• Solenoid valves
• Stopper gasket, pump discharge
weight, long spring, and discharge
large ball (a)
• Pump damping spring (b)
• Plunger retainer and small ball (c)
• AAP inlet plug (d)
• AAP outlet plug (e)
• Throttle positioner
• Power valve (f)
• Slow jet (g)
• Primary and secondary main jets(h)
• Primary and secondary small venturis
(i)
• Fast idle cam subassembly
• Secondary throttle valve diaphragm
• Throttle position switch (some models
only)
• Idle mixture adjusting screw

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IMPORTANT!
Do not remove the throttle valve and choke valve from their shafts.

INSPECTION OF CARBURETOR

General Cleaning Procedure

CLEANING DISASSEMBLED PARTS BEFORE INSPECTION

(a) With a soft brush and carburetor cleaner, wash and clean the cast parts.
(b) Clean off the carbon from around the throttle valve.
(c) Wash the other parts thoroughly in a carburetor cleaner.
(d) Blow all dirt and other foreign matter from the jets and fuel passages.

1. INSPECT FLOAT AND NEEDLE VALVE

(a) Inspect the pivot pin (1) for scratches
and excessive wear.

(b) Inspect the float (2) for broken lips
and wear in the pivot pin holes.

(c) Inspect the spring (3) for breaks and
deformation.

(d) Inspect the needle valve (4) and
plunger (5) for wear or damage.

(e) Inspect the strainer (6) for rust and
breaks.

2. INSPECT POWER PISTON

Make sure that the power piston moves
smoothly.

3. INSPECT POWER VALVE

Check for improper opening and closing
(sticking, etc.)

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4. INSPECT FUEL CUT-OFF SOLENOID
VALVE

(a) Connect the terminals to the battery.
(b) You should feel the click fro the

solenoid valve each time the battery
power is connected and disconnected.
If the solenoid valve is not operating
properly, replace it.
(c) Replace the O-ring.

5. INSPECT THROTTLE POSITION

(a) Connect ohmmeter probes to the
switch connector and switch body.

(b) With the rod not pushed in, check that
there is continuity.

(c) With the rod pushed in, check that
there is not continuity.

6. INSPECT COIL HOUSING

Using an ohmmeter, measure the
resistance between the terminal and coil
housing.

Resistance: 20-22 Ω at 200C (680F)
(Europe and General Countries)
17-19 Ω at 200C (680F)

(US and Canada)

7. INSPECT IDLE MIXTURE ADJUSTING
SCREW

Check for damage to the idle mixture
adjusting screw.

8. INSPECT SLOW JET, PRIMARY MAIN
JET AND SECONDARY MAIN JET

Check for clogging of each jet.

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ASSEMBLY OF CARBURETOR

NOTE: Use new gaskets and O-rings throughout.

Assembly of Carburetor Body

1. ASSEMBLE CARBURETOR BODY AND
FLANGE

(a) Install the idle mixture adjusting
screw.

IMPORTANT!
Do not tighten the idle mixture adjusting
screw too much.

(b) Install the washer to the throttle valve
shaft.

(c) Place a new gasket and body onto
the flange.

(d) Install a vacuum passage screw as
shown.

(e) Install the three screws.

2. INSTALL THROTTLE POSITION SWITCH
(some models only)

3. INSTALL SECONDARY THROTTLE
VALVE DIAPHRAGM
(a) Assemble the housing (1), diaphragm
(2), spring (3) and cap (4). Install the
four screws with the retainer.
(b) Position a new gasket.
(c) Install the diaphragm assembly with
the two screws.
(d) Connect the link from the secondary
throttle level.
(e) Install the throttle back spring.
(f) Install the throttle return spring.

4. INSTALL FAST IDLE CAM

Install the washer, fast idle cam, washer,
cam with the washer and bolt.

5. INSTALL NEW O-RING, SIGHT GLASS
AND SIGHT GLASS RETAINER

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6. INSTALL PRIMARY AND SECONDARY
SMALL VENTURIS
Install the primary and secondary small
venturis over new gaskets.

7. INSTALL AAP
(a) Install the small ball, AAP outlet plug
and short spring.

(b) Install the small ball and AAP inlet
plug.

(c) Install the diaphragm, spring and AAP
housing with the three screws.

8. INSTALL JETS AND POWER VALVE

(a) Install the primary and secondary
main jets with new gaskets.

REFERENCE:

The inner diameter of the secondary main
jet is large than the inner diameter of the
primary main jet.

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(b) Install the primary and secondary
passage plugs with new gaskets.

(c) Install the spring, washer, throttle
levers with the spring washer and
nut.

(d) Install the slow jet.

(e) Install the power valve.

9. INSTALL THROTTLE POSITIONER

10. INSTALL SOLENOID VALVE

Install the solenoid valve with a new
gasket to the carburetor.

11. INSTALL ACCELERATION PUMP
CHECK BALLS

(a) Install the large ball, long spring,
pump discharge weight and
stopper gasket for the outlet side.

(b) Using tweezers, insert the small
plunger ball and retainer.

(c) Install the pump damping spring.

Assembly of Air Horn

1. INSTALL AUTOMATIC CHOKE

(a) Install a new gasket.
(b) Align the bimetal spring and the

choke lever, and install the coil
housing.

(c) Align the body scale center line
and coil housing line, and tighten
the three screws.

(d) Check the valve action of the
choke.

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2. INSTALL VALVE SEAT

Install the valve seat with strainer
over a gasket into the fuel inlet.

3. ADJUST FLOAT LEVEL

(a) Install the needle valve, spring
and plunger onto the seat.

NOTE: After adjusting the float level,
install the clip onto the needle valve.

(b) Install the float and pivot pin.

(c) Allow the float to hang down by its
own weight.

(d) Using SSTs, check the clearance
between the float tip and air horn.

SST 09240-00014 and 09240-00020

NOTE: This measurement should be
made without a gasket on the air horn.
Float level: 7.2 mm (0.283 in.)

If not within specification, adjust by
bending the portion of the float lip
marked (A).

(e) Lift up the float and, using SST,
check the clearance between the
needle valve plunger and the float
lip.

SST 09240-00020

Float level (lowered position): 1.67 – 1.99
mm

(0.0657-0.0783
in.)

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If not within specification, adjust by
bending the portion of the float lip
marked (B).

(f) After adjusting the float level,
remove the float, plunger, spring
and needle valve.

(g) Assemble the pin clip onto the
needle valve.

4. INSTALL NEEDLE VALVE

ASSEMBLY, FLOAT AND PIVOT

PIN

Insert the float lip between the
plunger and clip when installing the
float.

5. INSTALL POWER PISTON

(a) Install the power piston spring and
piston into the bore.

(b) Install the retainer.
(c) Install the acceleration pump

plunger and boot.

6. ASSEMBLE AIR HORN BODY

(a) Install the eight screws with the
following parts:
♦ Choke and solenoid wire
clamps.
♦ Fuel pipe support
♦ Number plate

(b) Connect the choke opener link.

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(c) Install the pump arm to the air
horn with the pump plunger hole
and level aligned.

(d) Connect the choke link.
(e) Install the vacuum hoses.

ADJUSTMENT OF CARBURETOR
NOTE: Use SST 09240-00014 and 09240-
00020 to make the adjustment.
1. CHECK AND ADJUST THROTTLE

VALVE OPENING
(a) Check the full opening angle of

the primary throttle valve.
Standard angle: 900 from horizontal
plane
(b) Adjust by bending the 1st throttle

lever stopper.

(c) Check the full opening angle of
the secondary throttle valve.

Standard angle: 800 from horizontal
plane.

(d) Adjust by bending the secondary
throttle lever stopper.

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2. CHECK AND ADJUST KICK-UP
SETTING

(a) With the primary throttle valve
fully opened, check the clearance
between the secondary throttle
valve and body.

Kick-up clearance: 0.16 – 0.27 mm
(0.0063 – 0.0106 in.)

(b) Adjust by bending secondary
throttle lever.

3. CHECK AND ADJUST SECONDARY
TOUCH ANGLE

(a) Check the primary throttle valve
opening angle when the primary
kick-down lever just touches the
secondary kick-down lever.

Standard angle: 450 from horizontal
plane
(Europe & Gen. Countries)
520 from horizontal plane
(US and Canada)
(b) Adjust by bending the 1st kick-

down lever.

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4. SET AUTOMATIC CHOKE

(a) Set the coil housing scale mark
so that it is aligned with the
center line of the body.

NOTE: The choke valve fully closes
when the atmospheric temperature
reaches 30-C (860F).

(b) Depending on richness of air-fuel
mixture, turn the coil housing to
adjust the engine starting
mixture.
If too rich …. Turn clockwise
If too lean …. Turn
counterclockwise

5. CHECK AND ADJUST FAST IDLE
SETTING

(a) Set the throttle shaft lever to the
1st step of the fast idle cam as
shown.

(b) With the choke valve fully closed,
check the primary throttle valve
angle.
Adjust by turning the fast idle
adjusting screw.

Standard angle: 210 from horizontal
plane

6. CHECK AND ADJUST UNLOADER

(a) With the primary throttle valve
fully opened, check the choke
valve angle.

Standard angle: 410 from horizontal
plane

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(b) Adjust by bending the fast idle
lever.

7. CHECK AND ADJUST CHOKE
OPENER
(a) Set the fast idle cam.
While holding the throttle slightly
open, push the choke valve
closed, and hold it closed as you
release the throttle valve.

(b) Apply vacuum to choke opener
diaphragm.

(c) Check the choke valve angle.
Standard angle: 700 from horizontal

(Europe and Gen. Countries)
740 from horizontal plane
(US and Canada)

(d) Adjust by bending the relief lever.

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8. CHECK CHOKE BREAKER

(a) Set the fast idle cam.
While holding the throttle slightly
open, push the choke valve
closed, and hold it closed as you
release the throttle valve.

NOTE: Fully close the choke valve
and check the opening angle.

(b) Apply vacuum to choke breaker
diaphragm A.

(c) Check the choke valve angle.
Standard angle: 360 from horizontal
plane

(Europe & Gen. Countries)
380 from horizontal plane
(US and Canada)

(d) Adjust by bending the relief lever.

(e) Apply vacuum to choke break

diaphragm A and B.

(f) Check the choke valve angle.
Standard angle: 550 from horizontal

plane

(Europe & Gen. Countries)
580 from horizontal plane

(US and Canada)

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(g) Adjust by turning diaphragm
adjusting screw.

9. CHECK AND ADJUST PUMP
STROKE
(a) With the choke valve opened,
check the length of the stroke/
Standard angle: 4.0 mm (0.157 in.)

(b) Adjust the pump stroke by
bending the connecting link A.

10. CHECK AND ADJUST THROTTLE
POSITION SWITCH (some models
only)

(a) Connect an ohmmeter to the
connector and switch body.

(b) With the throttle valve fully open,
check that there is continuity.

(c) Slowly return the throttle valve
from the fully-open position. At
the point where there is no
continuity, measure the throttle
valve angle.

Standard angle: 90 from horizontal
plane
If this is out of standard, adjust the
throttle position switch adjusting screw.

11. CHECK FOR SMOOTH OEPRATION
OF EACH PART

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PRECAUTIONS:

o Observe Safety
o Wear Personal Protective Equipment
o Perform 5 S

QUALITY CRITERIA:

♦ Carburetor overhauled in accordance with the required steps and procedure.

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SELF-CHECK LO4–1

What are the general steps of carburetor overhauling?
1.
2.
3.
4.
5.
6.
7.
8.
9.

10.
11.

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ANSWER KEY LO4–1

1. Carburetor Identification
2. Disconnecting attachments to the carburetor
3. Carburetor removal
4. Carburetor disassembly
5. Carburetor cleaning and inspection
6. Replacement of parts and gaskets
7. Carburetor bench adjustments
8. Carburetor reassembly
9. Carburetor replacement
10. Replacing linkage, hoses and tubes, fuel lines, and electrical connections.
11. Carburetor adjustments

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PERFORMANCE TEST Date: 3rd
Learner’s Name
Test Attempt
Competency: Service Engine Mechanical System 1st 2nd

Directions: Level OVERALL EVALUATION
Achieved PERFORMANCE LEVELS
Call Instructor. Ask instructor to
assess your performance criteria 4 – Can perform this skills without
tasks and performance criteria below. supervision and with initiative
adaptability to problem situations.
You will be rated based on the
overall evaluation. 3 – Can perform this skill satisfactorily
without assistance or supervision.

2 – Can perform satisfactorily but requires
some assistance and / or supervision.

1 –Can perform parts of his skill
satisfactorily, but requires
considerable assistance and/or
supervision.

Instructor will initial level achieved

PERFORMANCE STANDARDS Yes No N/A
For acceptable achievement, all items should receive a “Yes” or

“N/A” response.

1. Fuel octane rating used in accordance with manufacturer’s

specification.

2. Data gathered and interpreted from American Petroleum

Institute.

3. Safety measure applied in dealing fuel.

4. Fuel pump types identified according to usage.

5. Classification of fuel pump obtained according to manufacturer’s
specification.

6. Service fuel pump according to service steps and procedure.
7. Tools and equipment used in accordance with industry

standard.
8. Correct carburetor adjustment obtained according to repair

manual.
9. Technical data accessed and interpreted from manufacturer’s

specification.
10. Carburetor overhauled in accordance with the required steps

and procedure.

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TERMS AND DEFINITIONS

Aeration – the pressure or addition of air bubbles to a liquid.

Air bleed – an orifice that controls the flow of air mixing with fuel.

Air – bleed jet – a jet through which air can be added progressively to a fuel flow to prevent
over enrichment.

Atomization – the process of reducing fuel to tiny droplets during carburetion.

Carburetion – the enrichment of a gas (usually air) by combining it with a hydrocarbon fuel
such a gasoline.

Carburetor – a vacuum – operated device that atomizes gasoline into a stream of air passing
through the device.

Check valve – a valve that opens in the direction of flow and closes to prevent flow in the
opposite direction.

Choke plate – a metal plate at the top of the carburetor air horn that can be closed to reduce
airflow and provide a rich mixture for starting and warm – up.

Circuit – a carburetor system that provides air – fuel mixture for a given running condition.

Curb idle speed – the normal idling speed of an engine.

de–icer – a chemical added to gasoline to prevent ice particles from forming and adhering to
cold metal surfaces.

Emulsion tube – a perforated tube immersed in a fuel. Air is passed through the tube to male
a frothy air-fuel mixture.

Enrichment circuit- a carburetor circuit that provides a richer air-fuel mixture during full –
power operation.

Evaporation – a procedure by which a liquid is turned into vapor.

Fast – idle cam – a stepped or tapered part connected between the choke plate and the
throttle plate; used to help the engine run faster during warm – up.

Feedback carburetor – a carburetor with a mixture control solenoid activated by a control
unit based on information fed back fro sensing units.

Float – a lightweight part that rests, or floats, on the surface of a liquid.

Float Bowl – a hollow fuel reservoir area within a carburetor from which fuel is drawn during
carburetor.

Flooding – a condition in which excess unvaporized fuel in the intake manifold prevents the
engine from starting.
Fuel filter – a device to trap and hold sediment, rust particles, and other contaminants in fuel.

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Fuel – vapor separator – a device that uses gravity to separate liquid fuel from vaporized fuel.

Gasohol – a mixture of alcohol (up to 10%) and gasoline.

Gasoline – the most common hydrocarbon motor fuel.

Hydrocarbon – a chemical substance made up primarily of hydrogen and carbon atoms.

Idle – discharge port – a fuel discharge port positioned just below the edge of the throttle
plate when it is closed for idling.

Idle – speed solenoid – an electrical solenoid used to position the throttle plate for proper
idle speed.

Idling – normal slow speed engine operation without the accelerator pedal depressed.

Impeller – a fan-like propeller that forces a fluid to flow.

Impeller pump – a pump with radiating blades that operates by drawing fuel in at its center
and forcing it outward through centrifugal action.

Iso–octane – a hydrocarbon fuel assigned an octane rating of 100 to which other motor fuels
are compared.

Jet – a precisely sized, calibrated hole in a hollow passage, through which fuel or air can
pass.

Leaded gasoline – gasoline containing tetraethyl lead.

Lean mixture – an air–fuel mixture containing more than 14.7 parts of air to one part of
gasoline, by weight.

Main body – the control section of a carburetor which contains the float bowl and most
passages, jets, and discharge ports.

Main metering circuit – a vacuum – operated fuel discharge system that draws fuel from a
tube inserted into the float bowl. It discharges the fuel in the venture area.

Mechanical fuel pump – a pump driven by engine power, usually from the camshaft, through
either an eccentric lobe or a lobe, a pushrod, and a rocker arm arrangement.

Metering – in carburetion, the addition of a measured amount of fuel into the air stream
passing through a carburetor.

Misfueling – adding leaded gasoline to vehicles with catalytic converters.

Octane rating – a measure of a motor fuel’s ability to resist ignition from heat and pressure.
Also, the anti – knock rating.

Percolation – boiling of fuel within the carburetor.

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Rich mixture – an air – gasoline mixture containing less than 14.7 parts of air to one part of
gasoline, by weight.

Side draft carburetor – a carburetor in which air flows through the barrel in a horizontal
direction.

Solenoid – a device that uses electromagnetism to exert a pulling or holding force.

Stoichiometric – a chemical term that indicates the proper or ideal mixture o chemicals for a
particular section.

Tetraethyl lead – an extremely toxic chemical lead compound added to gasoline to increase
its octane rating.

Throttle body – the lower section of a carburetor, which contains the throttle plates, idle
mixture passages, and adjusting screws.

Throttle bore – the opening in a carburetor through which air passes.

Throttle plate – a movable plate, or flap, in an opening at the bottom of a carburetor barrel.

Throttle position sensor – an electrical sending unit that relays information to a central
system about how far the throttle plate of the carburetor is open.

Throttle positioner – an electrical device that mechanically holds a throttle plate open.

Updraft carburetor – a carburetor in which air flows through the barrel in an upward, vertical
direction.

Vapor/fuel separator – a unit that separates fuel vapor from liquid fuel.

Vapor lock – a collection of vapor in an area of liquid fuel system, which prevents an engine
from receiving fuel.

Venturi – a narrow restriction in a carburetor bore that increases the velocity of air passing
through the barrel

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Learner’s Diary

DIARY NOTES

Record important dates, jobs undertaken and other workplace events that will
assist you in providing further details to your assessor.

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RECORD OF ACHIEVEMENT

Module: Servicing Gasoline Fuel System

Learning Outcome #1 : Explain Fuel Octane Rating

Assessment Criteria:

1. Fuel octane rating used in accordance with manufacturer’s specification.
2. Data gathered interpreted from American Petroleum Institute.
3. Safety measure applied in dealing fuel.

Comments:

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Learner has satisfied the above performance criteria.

Learner’s signature ……………………………………….

Trainer’s signature ……………………………………….

Date ……………………………………………………….

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RECORD OF ACHIEVEMENT

Module: Servicing Gasoline Fuel System

Learning Outcome #2 : Identify fuel pump types/ classification

Assessment Criteria:

1. Fuel pump types identified according to usage.
2. Fuel pump classified according to manufacturer’s specification.
3. Fuel pump serviced according to service steps and procedures.

Comments:

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Learner has satisfied the above performance criteria.

Learner’s signature ……………………………………….

Trainer’s signature ……………………………………….

Date ……………………………………………………….

Code No. Servicing Gasoline Fuel System Date Developed Date Revised Page #
Nov. 28,2003
ALT723309 84

RECORD OF ACHIEVEMENT

Module: Servicing Gasoline Fuel System

Learning Outcome #3 : Perform Carburetor Adjustment

Assessment Criteria:

1. Tools used according to industry standard.
2. Correct carburetor adjustment obtained according to repair manual.
3. Carburetor adjustment performed according to industry operating procedure.

Comments:

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Learner has satisfied the above performance criteria.

Learner’s signature ……………………………………….

Trainer’s signature ……………………………………….

Date ……………………………………………………….

Code No. Servicing Gasoline Fuel System Date Developed Date Revised Page #
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ALT723309 85

RECORD OF ACHIEVEMENT

Module: Servicing Gasoline Fuel System

Learning Outcome #4 : Overhaul Carburetor

Assessment Criteria:

1. Technical data accessed and interpreted from manufacturer’s specification.
2. Tools and equipment used in accordance with industry standard.
3. Carburetor overhauled in accordance with the required steps and procedure.

Comments:

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Learner has satisfied the above performance criteria.

Learner’s signature ……………………………………….

Trainer’s signature ……………………………………….

Date ……………………………………………………….

Code No. Servicing Gasoline Fuel System Date Developed Date Revised Page #
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ALT723309 86

Copyright TESDA
Centex: General Santos National School of Arts and Trades (GSNSAT)
Tiongson Street, Lagao, General Santos City

First Published OCTOBER 2003

This draft was prepared at the Competency – Based Learning Materials

Development Workshop conducted at the Cagayan de Oro (Bugo) School of Arts
and Trades, from 23rd to 27th October 2003.

It was based on the Competency Standard for Automotive service Technician
developed by the Skills Standard and Certification Office (SSCO), and the
Competency – Based Curriculum Instructional Modules developed by the National
Institute for Technical Vocational Education and Training (NITVET), Technical
Education and Skills Development Authority (Technical Education and Skills
Development Authority).

Some materials for contextual learning (Science, Mathematics and
Communication) were supplied by Academic Teachers.

This learning instrument was developed by the following personnel:

Technology Instructors: Ricardo D. Bacaling Jr.
Elesio V. Ardaniel

Academic Teachers: Maria Belina A. Hubahib
Theresa Celendro
Marlo R. Oraiz
Gaspar D. Sinoy

Vocational Institution Supervisor: Teresa E. Jamisola

Facilitator: Abel B. Elpedes

This work was produced with funding provided by TESDA.

Code No. Servicing Gasoline Fuel System Date Developed Date Revised Page #
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ALT723309 87