Performing Gas Engine Tune Up

Removing the Old Spark Plugs

1. Pull the hood release lever located under the dashboard.

2. Walk around to the front of the car, reach under the hood, find the latch and squeeze
it. Open the hood.

3. Find the spark plugs, located in a row
along one side of the engine (on an in-
line four-cylinder engine) and attached to
thick wires, called spark plug wires. Cars
with V-shaped engines (which can have
four, six or eight cylinders) will have
spark plugs and spark plug wires on both
sides of the engine.

4. Change one spark plug at a time, always
putting the plug wire back on before
changing the next spark plug

Warning:
Change one spark plug at a time, putting the wire
back on after you're done. If you pull all the wires
off at once, you may put them back on the wrong
spark plugs; this changes the firing order, and
your car will run badly or not at all. If you must
take all the wires off at once, label them with
white correction fluid or with masking tape and a
marker.

5. Pull off one spark plug wire where it
attaches to the plug. There is a little
rubber boot at the plug end of the wire;
pull on this part. Pulling higher up on the
wire can damage the spark plug wire and
cause it to separate.

6. Blow or wipe away any dirt or debris
around the spark plug. You do not want
anything to fall into the cylinder while the
spark plug is out.

7. With the spark plug socket and a ratchet,
remove the spark plug by turning it in a
counterclockwise direction. You may
need an extension for your ratchet if the
spark plugs are deep-set or not directly
accessible. Ratchets with flexible heads
are especially helpful for hard-to-reach
spark plugs.

8. Check the spark plug to make sure it needs replacing. A good spark plug should be
lightly coated with grayish brown deposits. If heavy deposits are present, if the spark
plug is black or if the electrode or core nose is damaged, the plug needs to be
replaced.

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Installing spark plugs

Torque is one of the most critical aspects of spark plug installation. Torque directly affects
the spark plugs' ability to transfer heat out of the combustion chamber. A spark plug that is
under-torqued will not be fully seated on the cylinder head, hence heat transfer will be
slowed. This will tend to elevate combustion chamber temperatures to unsafe levels, and
pre-ignition and detonation will usually follow. Serious engine damage is not far behind.

An over-torqued spark plug can suffer from severe stress to the Metal Shell which in turn
can distort the spark plug's inner gas seals or even cause a hairline fracture to the spark
plug's insulator...in either case, heat transfer can again be slowed and the above
mentioned conditions can occur.

The spark plug holes must always be cleaned prior to installation, otherwise you may be
torquing against dirt or debris and the spark plug may actually end up under-torqued, even
though your torque wrench says otherwise. Of course, you should only install spark plugs in
a cool engine, because metal expands when its hot and installation may prove difficult.
Proper torque specs for both aluminum and cast iron cylinder heads are listed below.

Spark plug type Thread Diameter Cast Iron Aluminum
Cylinder Head Cylinder Head
Flat seat type (with 18 ø mm
gasket) (lb-ft.) (lb-ft.)
14 ø mm
" 12 ø mm 25.3~32.5 25.3~32.5
10 ø mm
" 8 ø mm 18.0~25.3 18.0~21.6
10.8~18.0 10.8~14.5
" 18 ø mm 7.2~10.8
7.2~8.7
" 14 ø mm -- 5.8~7.2

Conical seat type (without 14.5~21.6 14.5~21.6
gasket)
10.8~18.0 7.2~14.5
Conical seat type (without
gasket)

Steps:

1. Hand-tighten each spark plug in place. If you feel any resistance, stop and start over to
prevent cross-threading.

2. Tighten the plugs with a socket wrench until snug. Do not overtighten.

3. Replace the spark plug wires. Usually, you will hear a soft pop when the plug wire
snaps onto the plug.

4. Start the engine. Listen. If the engine runs roughly or doesn't start, make sure the wires
are pushed all the way onto the new plugs.

Note: Improperly gapped plugs will make your car run roughly, start poorly and have bad
gas mileage. Always clean the threads before installing.

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INFORMATION SHEET LO3-2: Reading and Understanding Spark Plugs

A lot can be learned about your engine condition and what it sees by properly reading
and "understanding" your spark plugs. This information sheet will show you pictures as well
as explanations on causes and effects of what you see when viewing you spark plugs.

This spark plug is what a normal plug should look
like.

Grayish-tan to white in color indicates the plug is
operating at the proper heat range as well as
correct jetting and the cylinder is running healthy.

That vertical color band on the ceramic shows you where the
plug is indexed. Meaning that band is aimed slightly at the
exhaust valve. If the band is anywhere but here, it means that
the plug is not at it's optimum location. There is still
discussion as to whether indexing a plug is worthwhile, but on
many applications looking for that last horsepower doesn't
hurt.

Normal Condition

Excessive electrode wear, misfire during
acceleration and hard starting.

Simply put as in its description, it's worn out ... it looks ok
color wise, so replace it with same plug or at least compatible
heat range. You've all heard the term " If it works, don't fix it".
Don't look for flaws with this plug ... just blame yourself for not
changing it sooner.

Worn Out Condition

This is caused by foreign objects in the combustion
chamber or an improper plug reach where it
contacts the piston. Even a piece of carbon can do
this.

To solve this, make sure you have the correct length tip spark
plug as well as removing any foreign materials in the
combustion chamber. In some cases you may have
excessive carbon buildup on the backs of the intake valves
that will have to be addressed.

Mechanical Damage

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In cases of severe detonation, insulators may Detonation
become cracked or chipped. Improper spark plug
gap settings will also cause the insulator tip to
crack or chip.

Detonation is tricky ... make sure that you are using the
correct octane fuel first and then verify correct ignition timing.
Next check for an inoperative EGR system (if equipped) as
well as proper function of the Knock Sensor (if equipped).
Also, you will want to make sure you are using the correct
heat range plug.

On this symptom you will notice a chalky
appearance, white insulator, rapid electrode wear
as well as an absence of deposits. The actual shell
may also be discolored.

To cure this you must first verify that the plug is the correct
heat range, the ignition timing settings are correct, the air/fuel
mixture is not too lean, there are no vacuum leaks and that
the EGR valve (if equipped) is functioning properly.

These are light-brownish deposits that are Overheated
encrusted to the ground and/or center electrode(s). Ash Deposits
This situation is caused by oil and/or fuel additives.
This condition can cause misfires.

The cure for this is to verify worn valve guides or valve seals,
not using fuel additives, or you might even try changing fuel
brands. By the way, a hotter plug is what most people try to
fix this problem. You need to first understand that the plug is
NOT typically the problem.

Oily coating caused by poor oil control. Oil is
leaking past worn valve guides, piston rings, or on
some race engines a possible intake gasket leak
and then entering the combustion chamber.

Check for worn valve guides (NEVER knurl valve guides),
intake gasket sealing alignment, as well as worn cylinder
walls and piston rings. A leak down test is a good place to
start for what is causing this.

Oil Fouled

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This will usually look as a melted center electrode Initial Pre-ignition
and/or ground electrode. Sustained Pre-ignition

Check for incorrect heat range plug, over-advanced
timing, lean fuel mixtures, inoperative EGR valve or
Knock Sensor (if equipped) and also look for hot
spots or deposit accumulation inside the
combustion chamber.

If you or your engine builder took the time, all areas of
combustion chamber should have been de-burred to
eliminate this problem. This includes the sharp edges on the
chamber, piston top, and cylinder wall valve reliefs (if
applicable).

This will be pretty obvious ... melted and/or missing
center and/or ground electrodes as well as a
destroyed insulator.

Check for incorrect heat range plug, over-advanced timing,
lean fuel mixtures, inoperative EGR valve or Knock Sensor (if
equipped) and also look for hot spots or deposit accumulation
inside the combustion chamber.

If you or your engine builder took the time, all areas of
combustion chamber should have been de-burred to
eliminate this problem. This includes the sharp edges on the
chamber, piston top, and cylinder wall valve reliefs (if
applicable).

After you see this, you'd better look for possible internal
engine damage as well. (pistons, cylinder walls, valves, rings,
etc.)

These look as if they are small islands of
contaminants on the insulator. This is usually a
dirty carburetor bores or air intake as well as the
possibility of a dirty or faulty injector.

You must use aggressive carburetor and choke cleaner or
other solvent cleaner (a pressurized fuel injection service on
fuel injected vehicles or injector removal and cleaning) before
installing new spark plugs.

Splashed Deposits

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This is very common visual condition on our race
engines. Soft, black, sooty, dry-looking carbon.
This indicates a rich mixture, weak ignition or
wrong heat range plug (too cold).

You will first need to verify plug heat range. On carbureted
engines, check choke as well as choke pull-off (if equipped)
for proper function and adjustment. On fuel injected engines,
check for clogged injectors and the cold-start valve and
circuit. You also need to check for correct fuel pressure
settings.

Carbon Fouled

As a general rule on all computer-controlled engines, you need to also make sure that all
input signals to the computer are working and accurate. This includes, but is not limited to,
all temperature and pressure sensors as well as the EFI system components.

Lastly on all engines, check for vacuum leaks and weak spark or low voltage output. (Good
reason for a better coil and aftermarket ignition unit "amplifier").

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OPERATION SHEET LO3-1: Gapping the Spark Plug

Steps:

1. Find the chart listing the proper "gap" for your plugs in your car's repair manual. The
spark plug gap may also be on the sticker on the inside of the car's hood. The parts
store can provide you with this specification as well or read the basics below.

2. Insert the spark plug gapping tool in the
gap between the metal center electrode
and the metal side electrode of the
plug's tip.

3. Look at the tool's ruled edge and find
the gap's measurement. If it is too big,
bend the spark plug's end with the tool
to widen the gap. To make the gap
smaller, push the side electrode (the
metal part at the very top) against a
hard surface.

4. After adjusting, measure again. Repeat
this procedure until the gap matches
the specification listed in your car's
manual.

5. Repeat with each plug.

Note: Spark plug gap specifications are listed in inches and/or millimeters. The gapper will
have inches on one side and millimeters on the other.

Spark Plug Gapping Basics

Since the gap size has a direct affect on the spark plug's tip temperature and on the voltage
necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a
popular misconception that plugs are pre-gapped from the factory, the fact remains that the
gap must be adjusted for the vehicle that the spark plug is intended for. Those with
modified engines must remember that a modified engine with higher compression or forced
induction will typically require a smaller gap setting (to ensure ignitability in these denser
air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will
need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the
gap, the more voltage is needed to bridge the gap. Most experienced tuners know that
opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency.
It is for this reason that most racers add high power ignition systems. The added power
allows them to open the gap yet still provide a strong spark.

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• Proper gapping of the spark plug is necessary to get maximum spark energy, lowest
RFI release as well as what is best for the longevity of the secondary ignition
components (coil, cap, rotor, wires, plugs).

• When checking plug gaps, the correct way is to use ONLY wire gauges, though many of
us are using the slider style gapping tools. These flat or feeler gauge style gauges do
not accurately measure true width of spark plug gap.

• When increasing the gap size for our high performance applications utilizing advanced
ignition systems such as Mallory, Accel, Jacobs, Crane and Holley ... it is important
never to go more than plus or minus .008". This is to maintain parallel surfaces
between ground and the center electrodes.

• Something many people do not know is that with Higher Compression ratios and
Superchargers as well as Nitrous, in many cases smaller spark plug gaps must be used
as well as the use of a much hotter ignition system (see above). These higher cylinder
pressures require more energy to jump the spark plug gap.

• The rule of thumb on plug gaps is to open them up in .002" increments at a time. When
the car (race vehicle) begins to lose power or slow down then go back .001-.002" and
this in most cases is the optimum gap.

Remembering that the Ignition Unit, plug brand as well as heat range, cap and/or rotor styles and in many
cases fuel type or brand will change the optimum spark plug gap settings.

Lastly, NEVER use the porcelain insulator as a fulcrum point when setting these gaps. This
can cause damage to the spark plug.

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ASSESSMENT TASKS:

These assessment tasks should be completed when you are confident that you can
inspect/test spark plugs. Assessment needs to conform to the rules of evidence. Therefore:
• You will need to participate and complete the learning activities
• You will demonstrate tasks to the required standard

• You will answer oral and written questions
• You will complete the assessment tool

OBSERVATION CHECKLIST:

Self Component Trainer’s check
check
Competent Not yet
competent

Spark plugs are removed properly.
Plugs are inspected thoroughly and tested
for serviceability.
Result of inspection/testing is reported to
instructor.
Threads and plug holes are cleaned.

Spark plugs are reinstalled properly.

Tools are properly used and stored.

Work area is cleaned.

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QUALIFICATION : Automotive Servicing NC I

UNIT OF COMPETENCY : Perform Gas Engine Tune Up

MODULE TITLE : Performing Gas Engine Tune Up

LEARNING OUTCOME 4 : Check/replace fuel filter and air cleaner

ASSESSMENT CRITERIA:
1. Fuel filter and air cleaner are replaced.
2. Fuel filter is free of sediments and impurities.

RESOURCES:

1. Auto Mechanics, Theory and Service
by: de Kryger, Kobacik. Bono

2. Corolla, Service and Repair Manual
by: Gregory’s Scientific Publication

3. Lancer, Service and Repair Manual
by: Gregory’s Scientific Publication

4. Toyota Training Manual
by: Toyota

7. VHS/CD

6. Corolla, Owners Manual
by: Toyota

7. Communication Module

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LEARNING EXPERIENCES

Learning Outcome # 4: Check/replace fuel filter and air cleaner

Learning Activities Special Instructions

1. Perform checking/replacing fuel filter • Follow the procedures in Operation
of a gasoline engine with the Sheet LO4-1 “Check/Replace Fuel
presence of your instructor. Filter”

2. Learn about fuel filters. • Read Information Sheet LO4-1 “How
Air Filter Works”

3. Perform checking/replacing air filter on • Follow the procedures in Operation

a gasoline engine with the presence Sheet LO4-2 “Check/Replace Air

of your instructor. Filter”

4. Check your knowledge and skill in this • Complete the assessment tasks.
learning outcome.

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LO4 - CHECK/REPLACE FUEL FILTER AND AIR CLEANER

LEARNING OUTCOME:

At the end of this learning activity you should be able to check and replace fuel filter
and air cleaner of a gasoline engine.

TOOLS, EQUIPMENT AND MATERIALS:

• Running condition vehicle
• Vehicle service manual
• Screwdrivers: 3/16" Slotted, #2 Phillips, #2 Phillips with minimum 8" long blade
• Wrenches: 17mm Flare nut, 19mm Flare nut, 19mm Open, 7/8" Open
• Ratchet: 3/8" with 10mm socket.
• Pliers
• New fuel filter
• New air filter
• New breather filter

LEARNING ACTIVITIES:

Activity # 1: Checking/replacing fuel filter and air cleaner

a. Read Operation Sheet LO4-1, and then perform the activity with the presence
of your instructor.

b. Read Information Sheet LO4-1.

c. Perform checking/replacing air filter on a gasoline engine with the presence of
your instructor.

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OPERATION SHEET LO4-1: Check/Replace Fuel Filter

A clogged air or fuel filter can cause poor performance, cost you at the fuel pump, and
shorten engine life. This simple procedure guards against that. A good rule of thumb is
once or twice a year, or roughly once every 12,000 miles (19,320 km).
Steps:
1. Rest the vehicle for 24 hours to let any remaining fuel pressure bleed off.

Check valves in the fuel lines are meant to maintain pressure to help prevent vapor
lock.
2. Locate the fuel filter.
Note: The fuel filter is located on the
right side of the engine bay just in front
of the power steering fluid reservoir. To
provide room to work it is highly
recommended you remove the entire
air cleaner housing.

3. Remove the "snorkel tube" from the
front of the air cleaner housing. This is
a friction fit and if you squeeze the
sides you should be able to easily pop
it out. Undo the two clips holding the air
cleaner housing cover on and remove
the cover and air filter inside the
housing.

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4. Using the 3/8" ratchet and 10mm
socket remove the support bolt for the
left half of the air cleaner housing.
Remove the temperature sensor
connector by pushing and holding
down the metal clip and gently pulling
the connector off the back of the air
cleaner housing. The temperature
sensor will remain attached to the air
cleaner housing.

5. The mass air flow sensor has to be
rotated forward towards the front of the
car to unlock the bayonet lock that
holds the air cleaner housing and mass
air flow sensor together. To allow the
mass air flow sensor to rotate the hose
clamp holding it in position must be
loosened and the electrical connector
to the mass air flow sensor removed.
First use the 8" #2 Phillips screwdriver
to loosen the hose clamp. The clamp
can only be accessed by inserting the
screwdriver just to the right of the Idle
Speed Control unit which is located on
top of the intake manifold near the top
center of the engine bay. I was able to
use my right hand to reach around over
the top of the air cleaner housing and
use my right hand fingers to guide the
screwdriver in my left hand to the hose
clamp behind the Idle Speed Control.
Doing this also ensures the hose clamp
doesn't rotate making it very difficult to
put everything back together.

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6. Disconnect the electrical connector to
the mass air flow sensor by turning the
plastic locking ring and then gently
pulling the connector off of the mass air
flow sensor. The connector is shape
coded so you don't have to worry about
remembering proper pin alignment.

7. The mass air flow sensor can now be
rotated forward towards the front of the
car to unlock the bayonet lock between
it and the air cleaner housing. Rotate
the mass air flow sensor forward about
1 inch to completely disengage the
lock.

8. The air cleaner housing sits on two
rubber mounts. The housing can now
be lifted up about 3/4" to clear these
mounts and then it can be separated
from the mass air flow sensor. There is
a sealing gasket between the air flow
sensor and the air cleaner housing.
The gasket is held in place on the air
cleaner housing by three plastic fingers
and should not come out, but use care
to ensure the gasket isn't lost or
damaged. The last step to removing
the air cleaner housing is to disconnect
the rubber hose connected at the lower
left corner of the housing. With the air
cleaner housing in place the house
clamp is pretty well hidden behind the
forward right cylinder intake runner.

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By waiting until the air cleaner housing
is off of the rubber mounts and
disconnected from the mass air flow
sensor you can maneuver the air
cleaner housing and rubber hose to a
position that will allow you to loosen the
hose clamp and separate the hose
from the air cleaner housing. Removing
the air cleaner housing from the engine
bay is somewhat of a jigsaw puzzle
because of the tight fit. Be patient.

9. Now that the air cleaner housing is out
of the way there is plenty of room in
which to work. You'll need a good
supply of rags and a small can to catch
the gas that will inevitably come out of
the filter. Remove the connection near
the rear of the car first. Used a 19mm
open wrench on the filter side nut to
hold the filter steady and a 19mm flare
wrench on the fuel line nut to break the
connection. This connection was not
particularly tight and the leverage angle
of the wrenches is not too awkward.

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Once the fuel line was off, enough gas
came out to fill the can up about 1/3 of
the way.

10. Theoretically, you should be able to use a 17mm and 19mm flare wrench on the
connection towards the front of the car. However, it is up underneath the front of the
engine bay and the leverage angles are awkward. After 5 minutes of grunting and
groaning with no obvious movement of the two nuts I chose a different approach.

First, loosen the fuel filter hose clamp. Then put the 17mm flare wrench on and
braced it against the side of the engine bay to hold the fuel line steady. Finally, use
the 7/8" open wrench on the nut shaped portion of the fuel filter (side facing rear of
car) where the first connection had already been undone. This allowed a much better
leverage angle on the 7/8" wrench / fuel filter. Using this method you will be able to
get the fuel filter off. However, it left the 19mm nut that was originally part of the fuel
filter connected to the 17mm fuel line nut. Also, once the fuel filter started to come
loose another 1/3 of a cup of gas came pouring out from the already open end of the
filter (like opening the vent plug of a 5 gallon gas can).

The fuel line is supported by a bracket
a few inches farther forward in the
engine bay (see previous pictures). A
few inches farther upstream from the
bracket, the metal fuel line changes to
a rubber line. By loosening the fuel line
support bracket you can now move the
fuel line into a position that you could
use the 17mm and 19mm flare
wrenches with a good leverage angle
and will be able to finally separate the
two nuts.

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11. The fuel line support bracket is freed
up by loosening a 10mm bolt in the
right rear wheel well that screws into
the six-sided plastic nut on the support
bracket (see previous pictures). One
final note, there is a black plastic offset
washer between the fuel support
bracket and the side of the engine bay.
Don't forget to put this back in place
when putting everything back together.

All that remain is to put everything back together again pretty much in the reverse order you
took it all apart. The order was:

1. Reattach the fuel line support bracket (remembering the offset plastic washer!).

2. Insert new fuel filter and attach to the forward 17mm fuel line nut. Be careful to get the
filter oriented the proper direction. There should be an arrow on the fuel filter itself
(should point to the rear of the car) and the nut arrangement between the fuel lines and
filter are one directional, but just be sure.

3. Attach the other fuel line (19mm nut).

4. Secure the fuel filter hose clamp. Mark the mileage and date on the filter for future
reference.

5. Attach the rubber hose to the lower left corner of the air cleaner housing.

6. Set the air cleaner housing onto the two lower rubber support mounts and work the
mass air flow sensor into the back of the air cleaner housing being cognizant of the
sealing gasket.

7. Rotate the mass air flow sensor to the rear of the car to re-engage the bayonet lock
between the air flow sensor and the air cleaner housing.

8. Secure the 10mm support bolt on the upper left half of the air cleaner housing.

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9. Tighten the mass air flow sensor hose clamp with the 8" #2 Phillips screwdriver. Use
your right hand to hold the clamp in place while using a screwdriver in your left hand to
tighten the hose clamp.

10. Reattach the mass air flow sensor connector and the air cleaner housing temperature
sensor connector.

11. Replace the air filter, the air cleaner housing cover and the "snorkel tube."

Finally, start the car and check for leaks. It will probably take a couple tries before the car
will start up.

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INFORMATION SHEET LO4-1: How Air Filter Works

The resin-impregnated, heat-cured "paper"
element looks like a pleated sheet, and
most of the dirt particles are stopped at the
outside surface. A light coating of dirt
actually improves the filtering ability of the
paper. But soon the dirt builds up and even
starts filling the bottoms of the pleats,
restricting airflow. The paper also has
multiple layers, and if you looked at it under
a microscope, it would look like a forest
with an irregular crisscross of vines and
limbs–the fiber strands of the "paper."

It all looks random, but the premium-priced filter "papers" are more consistent in the sizes
of the pores than it seems, and a quality material is a mathematically predictable barrier to
dirt particles. In actuality, the layers of fibers form a maze and some of the dirt also is
trapped within the layers of the paper. The inrushing air produces some static electricity,
which also causes some smaller dirt particles to adhere to the surfaces of the paper fibers.

Air filters actually work better as the filter material fills up with debris. Holes are plugged by
fine particles, and fewer voids remain to pass other particles. But a point comes when not
enough voids remain to pass the air needed to supply your engine. The result is inadequate
oxygen to burn the fuel at wide-open throttle. With carbureted engines, this used to mean
rich running. Modern fuel-injected engines meter the air admitted to the intake and add
appropriate fuel–making for a clean-running engine that eventually won't get out of its own
way. At least carbureted cars coughed and sputtered to let you know that you had a
problem.

Metering the Air

Just downstream of the filter housing,
perhaps connected by a duct, will be the
engine's airflow meter, or sensor. (Some
engines have no airflow meter. Instead,
their computer calculates air intake using
rpm, intake vacuum and barometric
pressure.) Contamination of the airflow
meter will give your engine's computer
inaccurate information about the amount
(mass) of air the engine is burning. That
could mean poor driveability, poor mileage
and hard starting.

Some air-cleaner elements can be rotated 180
degrees to equalize dirt pickup, extending their
service life. Clean the housing's interior before

assembly.

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Don't, however, try to clean the airflow sensor, save for blowing loose dirt and cobwebs
with your breath. The calibration of these instruments is fragile, and you stand a good
chance of mucking your sensor up irreparably.

Finding cracks on the Duct

Before you install the new filter, inspect the Check the air cleaner's ductwork for leaks and splits,
duct from the throttle body to the filter especially if you're having driveability problems.
housing. Spread the flutes of the duct,
looking for cracks. If the duct is cracked, it Temporary repairs can be made with ordinary duct
may be closed at idle but spread on tape.
acceleration, when the engine torques.
That not only brings in unfiltered air, but on
today's engines with mass airflow sensors,
the dirty air also is "unmeasured." The
amount of fuel sprayed by the injectors is
determined by how much air is flowing in,
so if some of that airflow isn't measured by
the sensor, not enough fuel will be injected.
The engine will run lean and hesitate
and/or stumble. The same thing can occur
if the duct isn't properly fitted and clamped
at each end.

Find a crack? Well, it's a duct, so you can repair it with duct tape. That's a move that no
professional would make, because in time the tape will lose its grip in the heat of the engine
compartment, as the duct flexes. But it's your car, and if you are willing to recheck and
retape frequently, you can save the cost of the new part, or at least postpone the expense.

Fit Is Important

Carefully check the fit between the lips of the housing and the rubber gasket rimming the
filter. This gasket not only seals the filter housing's two halves together, but also provides
an airtight and dirt-tight seal between the filter and the clean side of the housing. Look
carefully at the old filter's gasket. It should show a smooth, clean line 360 degrees around
at the sealing face on both sides. The rim of the filter housing will have compressed the
rubber gasket if everything is correct. If not, a little detective work is in order. Is the filter the
correct part? If not, is your replacement filter the correct part? Don't rely on just a visual
comparison–look up the correct part number and cross-reference.

Were all of the spring clamps properly latched? Some air cleaners use screws to hold them
shut, while others use a large wing nut. All of the fasteners need to be tight, even that one
you can hardly see or reach next to the battery. On a few vehicles, the housing is attached
by a bolt or spring clamp that can be removed to allow the housing to be displaced an inch
or two, permitting big, American-sized hands to fit into a narrow space.

To install the filter element, clean out the housing first, wiping the inner surface with a cloth
lightly moistened with solvent. Insert the element so it seats properly. Filters have a specific
side up or toward the throttle body, and you have to install it correctly so the end seals line
up with the shape of the housing or its cover. If they don't, you won't get a good end seal,
and incoming air may bypass the filter and allow dirt into the engine.

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Code No. March 4, 2006 67

ALT723302

It's time to finish up. Install the cover or the halves of the filter housing. In addition to the
spring clips and wing nuts that hold the parts together, there also may be alignment tabs in
areas you can't reach with your fingers. Be sure the tabs are engaged as you fit the halves
together, so the two parts of the housing form an airtight joint when you turn the wing nuts
or engage the spring clips.

Be absolutely sure that both ends of any ductwork are properly sealed to both the air
cleaner body and the airflow meter or throttle body, including hose clamps or retaining
clips. Remember, that rubber hose will become soft when underhood temps rise, so don't
rely on the rubber's stiffness when it's cold.

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ALT723302 March 4, 2006 68

OPERATION SHEET LO4-2: Replacing Air Filter

Changing the air filter should be part of any major tune-up, but if you drive on dirt roads
or in other dusty conditions, you will need to replace it more frequently. On most cars,
this is a fairly simple procedure. You should change your car's air filter every 15,000
miles.
Steps:
1. Open the hood.
2. Locate your air filter, usually found on

top of the engine. On cars with
carburetors it is in a round piece of
metal about the size of a medium pizza;
fuel-injected cars have square or
rectangular air filter housings that may
be off to the side of the engine.

3. Unscrew or unclamp the top to the air
filter housing.

4. Lift out the air filter. It should be a round
or rectangular filter made of paper or
plastic, with a rubber rim.

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ALT723302 March 4, 2006 69

5. Clean the area with a vacuum cleaner or seal the top of the carburetor. This will
keep debris out of the carburetor as you continue to clean the housing.

6. Clean out any dirt or bugs from the
inside of the air filter housing with a rag.

7. Replace the filter with a new filter.
Consult your manual to determine the
proper filter for your car.

Check your old filter element for dirt, oil or
moisture, cracks and proper sealing at the gasket.

8. Replace the cover and close the hood.
Warning: Avoid using the wrong size air filter. Your engine will run less efficiently.
Note: Reusable air filters cost more than disposable filters, but if cared for correctly, they
can last for over 50,000 miles.
Another good way to make your air filter last is to actually use a vacuum cleaner. Simply
take the filter out and with the small attachments from the vacuum, suck out the dust and
dirt. Good as new and it will make your filter last a littler longer.

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ALT723302 March 4, 2006 70

ASSESSMENT TASKS:

These assessment tasks should be completed when you are confident that you can
check/replace fuel filter and air cleaner. Assessment needs to conform to the rules of
evidence. Therefore:
• You will need to participate and complete the learning activities
• You will demonstrate tasks to the required standard

• You will answer oral and written questions
• You will complete the assessment tool

OBSERVATION CHECKLIST:

Self Component Trainer’s check
check
Competent Not yet
competent

Fuel and air filters are removed properly.

Fuel and air filters are inspected carefully.

Result of inspection is reported to instructor.

Engine components are cleaned.

Fuel and air filters are installed/reinstalled
properly.

Tools are properly used and stored.

Work area is cleaned.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 71

QUALIFICATION : Automotive Servicing NC I

UNIT OF COMPETENCY : Perform Gas Engine Tune Up

MODULE TITLE : Performing Gas Engine Tune Up

LEARNING OUTCOME 5 : Test and replace ignition breaker

ASSESSMENT CRITERIA:

1. Ignition breaker is tested and replaced.

2. Condenser is tested and replaced

RESOURCES:

1. Auto Mechanics, Theory and Service
by: de Kryger, Kobacik. Bono

2. Corolla, Service and Repair Manual
by: Gregory’s Scientific Publication

3. Lancer, Service and Repair Manual
by: Gregory’s Scientific Publication

4. Toyota Training Manual
by: Toyota

8. VHS/CD

6. Corolla, Owners Manual
by: Toyota

7. Communication Module

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 72

LEARNING EXPERIENCES

Learning Outcome # 5: Test and replace ignition breaker

Learning Activities Special Instructions

1. Perform checking/replacing contact • Follow the procedures in Operation
point and condenser of a gasoline Sheet LO5-1 “Inspect/Replace
engine in the presence of your Ignition Breaker and Condenser”
instructor.

2. Check your knowledge and skill in this • Complete the assessment tasks.
learning outcome.

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ALT723302 March 4, 2006 73

LO5 - TEST AND REPLACE IGNITION BREAKER

LEARNING OUTCOME:

At the end of this learning activity you should be able to inspect and replace ignition
breaker and condenser of a gasoline engine.

TOOLS, EQUIPMENT AND MATERIALS:

• Running condition vehicle
• Vehicle service manual
• Screwdrivers: flat and Phillips head (magnetic)
• Dwell/tach meter
• Strobe timing light
• Wrench: 10 mm
• Feeler gauges
• New set of breaker points
• New condenser
• Grease
• Chalk

LEARNING ACTIVITIES:

Activity # 1: Test and replace ignition breaker

a. Read Operation Sheet LO5-1, and then perform the activity with the
presence of your instructor.

b. Perform testing and replacing contact breaker on a gasoline engine with
the presence of your instructor.

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ALT723302 March 4, 2006 74

OPERATION SHEET LO5-1: Testing and Replacing Ignition Breaker and
Condenser

Contact points should be replaced every 10,000 miles. It's good practice to replace the
condenser at the same time. When you replace the points, you then must check and, if
necessary, re-set the timing to specification.

1. Remove the distributor cap. You will
find that there are two spring clips
which hold it on.

2. Insert a screwdriver between each clip
and the distributor case, and pry them
off the cap. The cap then simply lifts off.
Do not remove the spark plug wires
from the distributor cap.

3. Remove the rotor by pulling it straight
up off the distributor shaft.

4. Remove the plastic dust cover by lifting
it off the distributor.

5. Remove the old contact points. You will
see that there is a screw that holds the
points unit to a plate inside the
distributor.

6. Loosen and remove this screw. Unplug
the wire from the points from the black
plastic plug that it's connected to. Just
pull it straight off.

7. Now withdraw the points and if they are
pitted/excessively worn, replace them. If
they look good, keep them as your
spare for an emergency.

8. Remove the condenser. The condenser
is that little metal can inside or outside
of the distributor. There is one screw
that holds the condenser on itself, and
there is another which holds the black
plastic plug to the distributor body. Both
of these screws are readily accessible,
so remove them and the little metal plug
clip, and then remove the condenser
and plug from the distributor.

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Reassembly

1. On the new condenser, find the plastic plug. You will see a groove in it that the metal
plug clip fits into.

2. Fit the plug into the clip and then fit the assembly to the distributor body and start the
screw. Try not to drop the screw. Once you've started the screw, go ahead and tighten it
down.

3. Next, you want to install the condenser itself. Rotate the distributor as needed. Install
the new condenser with the screw to the distributor body. Once that is done, run the
green wire to the same terminal on the ignition coil you took the old one from. It should
be the (-) terminal.

4. Now you need to install the points. First, take a little dab of grease and smear some on
the distributor shaft. The proper grease should come in a little packet with your new
points set. A little goes a long way. Now fit the points. You will notice that at the hinge
end of the points, there is a protrusion that fits into a hole in the points plate. Make sure
that is engaged properly. Then when it is, insert the hold-down screw and tighten it
some, but leave it loose to provide for adjustment later. The magnetic-tipped
screwdriver really helps with inserting that screw.

5. Use your wrench on the alternator/generator pulley to turn the engine over until the
points rubbing block is on one of the high points of the distributor shaft and the points
are fully open. Look at it straight on from above and make sure the points are on the
high point and are fully open.

6. When this has been achieved, grab your feeler gauge set in one hand and a flat-blade
screwdriver in the other. You are going to adjust the gap between the points. The
minimum gap is .016" and the range is .016" to .020". If in doubt, consult your manual
for the correct specification.

7. Pull out the appropriate size of feeler gauge and slide it between the points. Make sure
you are doing it straight on. The blade should slide through with slight resistance when
the gap is correct. If it needs to be adjusted, grab your flat-blade screwdriver. Look
down at the plate the points sit on, toward the tip of the points away from the points
hinge. You will see two small nubs on that plate. What you do is insert your screwdriver
between these two nubs and use them to lever the points open or closed, depending on
your needs. It's harder to describe than it is to do. So lever the points until the correct
gap is achieved, and then tighten down the screw. Check once more and if it is correct.
If it has changed, loosen the screw, adjust the gap, and tighten it again.

8. For Type 4 engines, rotate the distributor back as close to its original position as you
can. Re-attach the vacuum line and plug back in the cold start valve if you have fuel
injection.

9. Now you need to put the distributor back together. Put the plastic dust cover back on,
then the rotor. Notice that the distributor shaft has a cutout that fits a protrusion on the
rotor. The rotor will only go back on one way. Press the rotor down onto the shaft and
then wiggle it a bit while pushing down on it to make sure it is seated properly. Then
replace the distributor cap. It is notched on one end as is the distributor body, so the
cap will only go on one way.

10. You may wish at this time to replace the distributor cap and rotor. If so, substitute the

new rotor for the old one when you place it on the shaft above. Then orient the new

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ALT723302 March 4, 2006 76

distributor cap correctly regarding the notch. Now transfer the spark plug wires ONE BY
ONE to the new distributor cap. Make sure they are all fully seated in the new cap. Fit
the cap to the distributor body and then re-engage the spring clips.

11. Start the engine. It should start up just fine. Type 4 engines who had to turn the
distributor may find it running roughly, but it will improve on adjusting the timing.

12. Attach your tach/dwell meter according to the manufacturer's instructions. Using a
digital model, attach the red (+) cable goes to the (+) terminal on the coil, and the black
(-) cable goes to the (-) terminal on the coil. Then turn the knob to "Dwell, 4-cyl" and
observe the reading. It should be within the specification. Anywhere from 44 to 50
degrees of dwell is acceptable. If it is out of range, you need to go back in and adjust
the point gap until it is within specifications. Making the point gap narrower increases
the dwell reading and widening it decreases the reading, since the dwell is the number
of degrees of rotation during which the points are closed. Too narrow a point gap can
lead to burning of the points, which destroys them, and too wide a gap can lead to
misfiring under high rpm and high load conditions.

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ALT723302 March 4, 2006 77

ASSESSMENT TASKS:

These assessment tasks should be completed when you are confident that you can
check/replace fuel filter and air cleaner. Assessment needs to conform to the rules of
evidence. Therefore:
• You will need to participate and complete the learning activities
• You will demonstrate tasks to the required standard
• You will answer oral and written questions
• You will complete the assessment tool

OBSERVATION CHECKLIST:

Self Component Trainer’s check
check
Competent Not yet
competent

Distributor cap is removed properly.

Contact points and condenser are inspected
carefully.

Result of inspection is reported to instructor.

Engine components are cleaned.

Ignition breaker and condenser are installed/
replaced properly.

Tools are properly used and stored.

Work area is cleaned.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 78

QUALIFICATION : Automotive Servicing NC I

UNIT OF COMPETENCY : Perform Gas Engine Tune Up

MODULE TITLE : Performing Gas Engine Tune Up

LEARNING OUTCOME 6 : Check/adjust ignition distributor setting

ASSESSMENT CRITERIA:
1. Ignition distributor is checked
2. Ignition distributor setting is adjusted

RESOURCES:

1. Auto Mechanics, Theory and Service
by: de Kryger, Kobacik. Bono

2. Corolla, Service and Repair Manual
by: Gregory’s Scientific Publication

3. Lancer, Service and Repair Manual
by: Gregory’s Scientific Publication

4. Toyota Training Manual
by: Toyota

9. VHS/CD

6. Corolla, Owners Manual
by: Toyota

7. Communication Module

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 79

LEARNING EXPERIENCES

Learning Outcome # 6: Check/adjust ignition distributor setting

Learning Activities Special Instructions

1. Perform testing/adjusting dwell angle • Follow the procedures in Operation
and ignition setting of a gasoline Sheet LO6-1 “Checking/Adjusting
engine with the presence of your Dwell Angle and Ignition Setting”
instructor.

2. Check your knowledge and skill in this • Complete the assessment tasks.
learning outcome.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 80

LO6 - TEST/ADJUST DWELL ANGLE AND IGNITION SETTING

LEARNING OUTCOME 5:

At the end of this learning activity you should be able to inspect and replace contact
point condenser of a gasoline engine.

TOOLS, EQUIPMENT AND MATERIALS:

• Running condition vehicle
• Vehicle service manual
• Screwdrivers: flat and Phillips head (magnetic)
• Dwell/tach meter
• Strobe timing light
• Wrench: 10 mm
• Feeler gauges
• New set of breaker points
• New condenser
• Grease
• Chalk

LEARNING ACTIVITIES:

Activity # 1: Check/adjust ignition distributor setting

a. Read Operation Sheet LO6-1, and then perform the activity with the
presence of your instructor.

b. Perform dwell angle adjustment and set the ignition timing.

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ALT723302 March 4, 2006 81

OPERATION SHEET LO6-1: Check/Adjust Dwell Angle and Ignition Setting

Dwell* or dwell angle is the number of
degrees the distributor shaft rotates
measured from the point where the ignition
contacts close to the point where they open
again.

Dwell angle is inversely proportional to
point gap, that is, increasing the gap
decreases the dwell, and vice versa.
Insufficient dwell may cause ignition failure
at high speed, while too much dwell
increases the total average current which
the points must handle, particularly at low
speed. This usually leads to very short
point life.

After a distributor is initially timed for a
given engine, any change in dwell will
result in a change in timing, requiring re-
timing of the distributor since the rubbing
block of the moving arm will contact the
cam in a different place.

Set the point dwell to the lower limit for new
points to allow for rubbing-block wear when
a dwell specification is given with a high
and low limit.

Parts of a distributor assembly.

*The percent of dwell is the percentage of the actual dwell angle of the points as
compared to the maximum, dwell angle possible (100 percent dwell). The 100 percent
dwell for 4, 6, and 8 cylinder engines, and some examples of percent of dwell are listed
in Table 1.

TABLE 1

No. of Maximum cylinders dwell angle (100% dwell)

4 cylinder = 90° 6 cylinders = 60° 8 cylinders = 45°

Comparison of percent of dwell and dwell angle

Percent of Calculation Corresponding dwell dwell angle
60% (.60) (90°) 54°
60% (.60) (60°) 36°
60% (.60) (45°) 27°

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March 4, 2006 82
ALT723302

CONTACT POINT GAP AND DWELL (Cam Angle Relationship)

If a distributor cannot be adjusted so that gap and dwell are within specifications at the
same time inspect the distributor for the following possibilities:

a. Improper spring tension or sticky pivot.
b. Wrong point set installed.
c. Bent shaft, causing point opening to vary on each cam lobe.
d. Worn cam lobes or defective cam, as above. (Compare gap at each cam lobe if in

doubt.)
e. Points floating, or not following the cam at high speeds.
f. Excessive resistance causing false dwell reading. In practically every case the

remedy will be self-evident.

CHECKING/ADJUSTING FOR PROPER DWELL ANGLE

1) Connect the dwell meter as per its manufacturer's instructions: Generally one of two
leads is connected to the positive terminal of the battery and the other lead to the
negative terminal of the coil.

2) Start the engine and read the dwell
angle (making sure meter is set on 4
cylinder).

3) If dwell angle is too high (points closed
for too many degree of rotation), you
will have to carefully reset your points to
a slightly larger gap. If the dwell angle is
too low, the points will need to be set
slightly closer. Adjust the gap .002" or
.003" at a time for best control.

4) Restart the engine and re-measure Top view of distributor (cap removed) showing
dwell angle. Repeat as above until contact breaker points.
dwell angle is correct.

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ALT723302 March 4, 2006 83

SETTING IGNITION TIMING

1. Set the timing by connecting the light (inductive or direct) and then mark the correct
timing position on the crank pulley or damper.

Note: Connect the power lead to the + terminal on the battery or the + side of the coil
and the other wire to ground.

2. Follow your engine manual and make an easy-to-read mark with White-Out (liquid
paper) or chalk.

3. Disconnect the vacuum line from the distributor and stick a pencil or nail into it to
prevent a vacuum leak.

4. Start the engine and get it running about 500-600 rpm to prevent any action from the
centrifugal advance mechanism (if there is one) and then slowly rotate the distributor
until the timing mark lines up with its pointer.

5. Tighten the hold-down on the distributor. If the engine won't run slowly enough back off
on the accelerator linkage at the carburetor. If the engine runs too slow increase the idle
speed.

6. Check the timing again and then put the light away.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 84

ASSESSMENT TASKS:

These assessment tasks should be completed when you are confident that you can
check/replace fuel filter and air cleaner. Assessment needs to conform to the rules of
evidence. Therefore:
• You will need to participate and complete the learning activities
• You will demonstrate tasks to the required standard
• You will answer oral and written questions
• You will complete the assessment tool

OBSERVATION CHECKLIST:

Self Component Trainer’s check
check
Competent Not yet
competent

Dwell angle is adjusted to specifications.

Ignition timing is set.

Result of dwell angle adjustment is reported
to instructor.

Engine components are cleaned.

Setting of ignition timing is reported to
instructor.

Tools are properly used and stored.

Work area is cleaned.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 85

QUALIFICATION : Automotive Servicing NC I

UNIT OF COMPETENCY : Perform Gas Engine Tune Up

MODULE TITLE : Performing Gas Engine Tune Up

LEARNING OUTCOME 7 : Set fuel mixture and idle rpm

ASSESSMENT CRITERIA:

1. Fuel mixture and idle speed (rpm) is adjusted
2. Advanced timing is checked

RESOURCES:

1. Auto Mechanics, Theory and Service
by: de Kryger, Kobacik. Bono

2. Corolla, Service and Repair Manual
by: Gregory’s Scientific Publication

3. Lancer, Service and Repair Manual
by: Gregory’s Scientific Publication

4. Toyota Training Manual
by: Toyota

5. VHS/CD

6. Corolla, Owners Manual
by: Toyota

7. Communication Module

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 86

LEARNING EXPERIENCES

Learning Outcome # 7: Set fuel mixture and idle rpm

Learning Activities Special Instructions

1. Adjust engine idle speed and mixture • Follow the procedures in Operation
of a gasoline engine with the Sheets LO7-1 “Adjust Engine Idle
presence of your instructor. Speed” and LO7-2 Adjust Carburetor
Air-Fuel Mixture”

2. Check your knowledge and skill in this • Complete the assessment tasks.
learning outcome.

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ALT723302 March 4, 2006 87

LO7 - SET FUEL MIXTURE AND IDLE RPM

LEARNING OUTCOME:

At the end of this learning activity you should be able to set the air-fuel mixture and
idle speed (rpm) of a gasoline engine.

TOOLS, EQUIPMENT AND MATERIALS:

• Running condition vehicle
• Vehicle service manual
• Screwdrivers: flat and Phillips head (magnetic)
• P 227 Carburetor Synchronizer
• Wrench: 10 mm

LEARNING ACTIVITIES:

Activity # 1: Adjust engine idle speed and mixture

a. Read Operation Sheets LO7-1 and LO7-2, and then perform the
activities with the presence of your instructor.

b. Adjust engine idle speed and mixture of a gasoline engine with the
presence of your instructor.

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ALT723302 March 4, 2006 88

OPERATION SHEET LO7-1: Adjust Engine Idle Speed

An improper air-to-fuel mixture results in bad engine performance and higher gas
consumption. Shown here are the steps in adjusting engine idle speed.

Procedure:

1. Determine if your car has a carburetor by checking your owner’s manual. Try looking
below the air filter to find the carburetor.

2. Be sure the engine is shut off then open the hood.

3. Remove the air filter by first
unscrewing the wing nut on top. No
need to disconnect any hoses
connected to the air filter - just
carefully set it aside.

4. The carburetor is the part that the air
filter was screwed into. The air/fuel
mixture is adjusted by two screws.
Typically, these screws can be found
on the lower-front section of the
carburetor.

5. Using a flat-head screw driver, turn
both screws to the right until they stop.
Do not tighten because this could
damage the needle points.

5. Loosen each screw, one at a time, 2 1/2 turns out.

7. Replace the air filter assembly and start the car.

8. If ideal idling speed is different from service manual (usually 1,200 – 1,300 rpm), adjust
idle accordingly by turning the screws in small increments.

9. Check accelerator pedal stop bolt and adjust if necessary. When the accelerator pedal
is depressed against the stop bolt, the carburetor arm should be clearing the carburetor
stop block by about 1 mm (.039 in).

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ALT723302 March 4, 2006 89

OPERATION SHEET LO7-2: Adjust Carburetor Air-Fuel Mixture.

1. Make sure the engine is off then open the hood.

2. Remove the air filter by first unscrewing the wing nut on top. No need to disconnect any
hoses connected to the air filter - just carefully set it aside.

3. The carburetor is the part that the air filter was screwed into. The air/fuel mixture is
adjusted by two screws. Typically, these screws can be found on the lower-front section
of the carburetor.

4. Using a flat-head screw driver, turn both screws to the right until they are tight.

5. Loosen each screw, one at a time, 2 1/2 turns out.

6. Replace the air filter assembly and start the car.

7. Adjust idle accordingly.

8. A vacuum gauge is essential. Hook it
up to intake manifold vacuum at any
available place, or use an adaptor.
Timing (ignition) plugs, wires, etc.
should already be completed. Engine
should be at operating temperature
(Choke should not be engaged).

9. Adjust idle speed per vehicle emissions
specs (sticker under hood will display
this).

10 Adjust the fuel mixture usually by
turning idle screw inwards (right)
lessens the amount of fuel. By turning
the screw all the way in and backing out
2 1/2 turns gives you a place to start.
If your carburetor has two screws turn them BOTH the same amount. By then turning
the screw(s) in at 1/2 turn increments, letting the engine run for a few seconds, or
"blipping" the throttle, you will hear and notice the engine operation change slightly.
When the speed drops off, (engine may shudder) you have gone too far.

11. Turn screw(s) back out 1/4 turn until the engine runs smoothly.

12. Let the engine run for a minutes. If done properly, you now have a lean burn setting on
your fuel mix. DO NOT GO BACK AND FIDDLE WITH YOUR IDLE SPEED OR
TIMING. IF YOU DO YOU WILL HAVE TO DO IT ALL OVER AGAIN. THE FUEL
MIXTURE ADJUSTMENT IS THE LAST THING YOU DO.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 90

ASSESSMENT TASKS:

These assessment tasks should be completed when you are confident that you can
check/replace fuel filter and air cleaner. Assessment needs to conform to the rules of
evidence. Therefore:
• You will need to participate and complete the learning activities
• You will demonstrate tasks to the required standard

• You will answer oral and written questions
• You will complete the assessment tool

OBSERVATION CHECKLIST:

Self Component Trainer’s check
check
Competent Not yet
competent

Engine speed (rpm) is checked and adjusted
properly.

Carburetor air-fuel mixture is adjusted
properly.

Adjustment settings are reported to
instructor.

Engine components are cleaned.

Tools are properly used and stored.

Work area is cleaned.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 91

QUALIFICATION : Automotive Servicing NC I

UNIT OF COMPETENCY : Perform Gas Engine Tune Up

MODULE TITLE : Performing Gas Engine Tune Up

LEARNING OUTCOME 8 : Perform compression test

ASSESSMENT CRITERIA:

1. Compression test is performed.
2. Compression test result is interpreted and appropriates recommendations is

prescribed.

RESOURCES:

1. Auto Mechanics, Theory and Service
by: de Kryger, Kobacik. Bono

2. Corolla, Service and Repair Manual
by: Gregory’s Scientific Publication

3. Lancer, Service and Repair Manual
by: Gregory’s Scientific Publication

4. Toyota Training Manual
by: Toyota

5. VHS/CD

6. Corolla, Owners Manual
by: Toyota

7. Communication Module

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 92

LEARNING EXPERIENCES

Learning Outcome # 8: Perform compression test Special Instructions
Learning Activities

1. Perform compression testing of a • Follow the procedures in Operation
gasoline engine with the presence of Sheet LO8-1 “Performing
your instructor. Compression Test”

2. Check your knowledge and skill in this • Complete the assessment tasks.
learning outcome.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

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LO8 - PERFORM COMPRESSION TEST

LEARNING OUTCOME:

At the end of this learning activity you should be able to perform compression test on
a gasoline engine.

TOOLS, EQUIPMENT AND MATERIALS:

• Running condition vehicle
• Vehicle service manual
• Basic hand tool set
• Compression gauge
• Safety glasses

LEARNING ACTIVITIES:

Activity # 1: Conduct compression test

a. Read Job Sheet LO8-1, and then perform the activity with the presence
of your instructor.

b. Interpret compression testing result on an actual engine and recommend
appropriate solutions to compression problems encountered.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 94

JOB SHEET LO8-1: Perform Compression Testing

The cylinder compression tester measures the ability of the cylinders to hold compression
while the starting motor cranks the engine. The compression tester is a pressure gauge
that measures the amount of pressure or compression, built-up in the cylinder during the
compression stroke. How well a cylinder holds compression is an indication of the condition
of the piston, piston rings, cylinder wall, valves and head gasket.

1. Warm up the engine to operating temperature.

2. Stop the engine.

3. Remove the injector or injection nozzles.

4. Connect a pressure gauge to the
cylinder port as shown.

Figure LO7-1.

5. Set the engine speed control to stop position.

6. Turn the engine with the starter until the pressure gauge registers no further rise in
pressure.

Note: It is a good practice to count the number of compression strokes, indicated by movement of
the gauge needle, and check each cylinder with the same number of strokes. The engine
must be at full cranking speed or as specified in appropriate service manual to get a good
reading.

7. Check the pressure reading against the engine technical manual.

Note: Low pressure indicates leakage through valves, rings or gaskets. Variations in cylinder
pressures of more than 10% usually indicate a need for cylinder reconditioning.

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 95

Results of Compression Test

Engine compression readings are usually considered normal if the lowest reading is 75
percent or more of the highest.

For example, if one cylinder in an engine has a compression pressure of 120 psi (828
kPa), then all cylinders should have compression readings of 90 psi (621 kPa) or higher.
Typical compression pressures vary among engines and manufacturers. In many
General Motors engines, no cylinder should have a compression pressure of less than
100 psi (690 kPa). Toyota specifies a maximum compression pressure of 142 psi (990
kPa) in some engines. The following section describes interpreting the results of the
compression test.

The manufacturer’s specification show what the compression pressures should be. If
compression is low, there is leakage past the piston rings, valves or cylinder-head
gasket. If the readings vary, how they vary may indicate the cause of the problem.

A Compression test made as described in Figure LO7-2 is a dry compression test. In a
spark-ignition engine, a second or wet compression test will help locate the leak. Squirt
about 1 tablespoon [15 cc] of engine oil through the spark-plug hole into the cylinder.
Recheck the compression.

Caution: Never perform a wet compression test on a diesel engine. The heat of a compression
could ignite the oil and damage the compression tester. Also, since the oil is not
compressible, it could fill the combustion chamber and create a hydrostatic lock. This
prevents the crankshaft from turning and may damage the engine.

If the compression pressure increases Compression Gauge Possible Engine
to a more normal value, the low
compression probably is due to Reading Condition
leakage past worn piston rings.
Adding oil helps seal the rings Fails to climb during Valve sticking open
temporarily as the cylinder holds
compression better. Other possible all compression
causes are a worn piston or cylinder
wall, and rings that are broken or strokes
stuck in their piston-ring grooves.
20 PSI (138 kPa) Faulty rings or valve
If adding oil does not increase
compression pressure, the leakage below normal seating
may be past the valves. Possible
causes include: More than 20 PSI (138 Faulty head gasket

kPa) below normal in

two cylinders next to

each other

20 PSI (138 kPa) Excessive carbon

above normal buildup in

combustion

chamber

Figure LO8-2. Compression-gauge readings and

the probable engine conditions. (Ford Motor

Company)

1. Broken valve springs
2. Incorrect valve adjustment
3. Sticking valves, valves not seating
4. Worn or burned valves
5. Worn or burned valve seats
6. Worn camshaft lobes
7. Dished or worn valve lifters

Code No. Performing Gas Engine Tune Up Date: Developed Date: Revised Page #

ALT723302 March 4, 2006 96