\EPA-450/3-77-036/
November 1977.
MOTOR VEHICLE
EMISSIONS CONTROL.
BOOK ONE
POSITIVE CRANKCASE
VENTILATION SYSTEMS
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
I
3
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EPA-450/3-77-036
MOTOR VEHICLE EMISSIONS CONTROL
BOOK ONE
POSITIVE CRANKCASE
VENTILATION SYSTEMS
by
B.D. Hayes, Project Director
M.T. Maness, Associate Project Director
R.A. Ragazzi, Principal Investigator
R.A. Barrett, Graduate Research Assistant
Department of Industrial Sciences
Colorado State University
Fort Collins, Colorado 80523
EPA Grants No. T008135-01-0 and T90Q621-01-0
EPA Region VIII Project Officer: Elmer M. Chenault
EPA Project Officer: Bruce Hogarth
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Control Programs Development Division
Research Triangle Park, North Carolina 27711
November 1977
-------
Copies of this publication are available free of charge to Federal employees,
current contractors and grantees, and nonprofit organizations - as supplies
permit - from the Library Services Office (MD-35), Environmental Protection
Agency, Research Triangle Park, North Carolina 27711; or, for a fee, from
the National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia 22161.
This report was furnished to the Environmental Protection Agency by the
Department of Industrial Sciences, Colorado State University, Fort Collins,
Colorado, 80523, through Grants No. T008135-01-0 and No. T900621-01-0.
The contents of this report are reproduced herein as received from Colorado
State University. The opinions, findings, and conclusions expressed are
those of the authors and not necessarily those of the Environmental Protection
Agency. Mention of company or product names is not to be considered as
an endorsement by the Environmental Protection Agency.
Publication No. EPA-450/3-77-036
11
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MOTOR VEHICLE EMISSIONS CONTROL
- SERIES OF SEVEN BOOKS --
MOTOR VEHICLE EMISSIONS STAFF, COLORADO STATE UNIVERSITY
BOOK ONE - POSITIVE CRANKCASE VENTILATION SYSTEMS
BOOK TWO - THERMOSTAT1C AIR CLEANER SYSTEMS
BOOK THREE - AIR INJECTION REACTION SYSTEMS
BOOK FOUR - FUEL EVAPORATION CONTROL SYSTEMS
BOOK FIVE - EXHAUST GAS RECIRCULATION SYSTEMS
BOOK SIX - SPARK CONTROL SYSTEMS
BOOK SEVEN - CATALYTIC CONVERTER SYSTEMS
111
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ACKNOWLEDGMENTS
The Motor Vehicle Emissions Control Staff of the Department
of Industrial Sciences at Colorado State University would
like to acknowledge the efforts extended by the Environmental
Protection Agency, Research Triangle Park, and Region VIII
Environmental Protection Agency, Manpower Development
Division.
A special thanks must be extended to the automotive vehicle
equipment and parts manufacturers for their cooperation and
assistance in the development of this training material.
IV
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INSTRUCTIONS FOR THE USE OF THIS BOOK
This book is one of a series designed specifically to teach the concepts
of automobile emissions control systems. Each book is designed to be
used as self-instructional material. Therefore, it is important that
you follow the step-by-step procedure format so that you may realize the
full value of the emissions system which is being presented. The topics
are taught in incremental steps and each topic treatment prepares the
student for the next topic. Each book is divided into sections which
include the introduction, purpose, function, inspection and testing of
the emissions system presented.
As you proceed through this series, please begin with book one and read
the following books in sequence. This is important because there are
several instances where material covered in a given book relies on
previously covered material in another book.
To receive the full benefits of the book, please answer the self-
evaluation statements related to the material. These statements are
separated from the text by solid lines crossing the page. The answers
to the statement can be found at the end of the book as identified by
the table of contents. You should check for the correct answer after
you respond to each statement. If you find that you have made a mistake,
go back through the material which relates to the statement or statements.
Fill-in-the-blank statements are utilized for self-evaluation purposes
throughout the material. An example statement would appear like this:
The American flag is red, white, and
You would write "blue" in the blank and immediately check your answer at
the end of the book.
v
-------
The material, statements and illustrations should be easy to follow and
understand. In several illustrations a small ghost named "VEC" (Vehicle
Emissions Control) has been used to make the picture easier to understand.
Upon completion of this series, you should be able to better understand
the emissions control systems and devices which are an integral part of
automobiles today. Your increased knowledge should help you keep these
"emissions controlled" vehicles operating as they were designed to
operate. Respectable fuel economy, performance and driveability, as well
as cleaner air, can be obtained from the automobile engine that has all
of its emissions systems functioning properly.
vi
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CONTENTS
Introduction to Emissions Control 1-1
Hydrocarbons 1-1
Carbon Monoxide 1-1
Oxides of Nitrogen 1-2
Formation of Hydrocarbons 1-2
Formation of Carbon Monoxide 1-3
Formation of Oxides of Nitrogen 1-3
Ignition Timing 1-3
Carburetion 1-5
System Introduction 1-7
System/Component Purpose 1-13
Type One PCV System 1-13
Type Two PCV System 1-14
Type Three PCV System 1-16
Type Four PCV System 1-17
System/Component Function 1-19
Type One PCV Valve 1-19
Type Two West Coast Control Valve 1-22
Type Three PCV System 1-25
Type Four PCV System 1-26
System Inspection 1-33
System Testing 1-35
RPM Drop Test 1-35
Vacuum Draw Test 1 1-36
Vacuum Draw Test 2 1-37
Summary 1-41
Answers . » 1-43
vii
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INTRODUCTION TO EMISSIONS CONTROL
As we all know emissions systems and devices have been installed on the
automobile engine because of the air pollution problem. In order for
you to understand these emissions systems and devices you should have a
background of the problem. All of the emissions control systems were
installed on the engine to reduce just three specific exhaust products.
These are known as products of combustion. The three products which the
emissions systems are designed to reduce are hydrocarbons, carbon monoxide
and oxides of nitrogen.
HYDROCARBONS
Gasoline, like all petroleum products, is made up of hundreds of hydro-
carbon compounds. The name "hydrocarbon" has been given to these com-
pounds because they are made up of hydrogen and carbon atoms. This is
also the reason hydrocarbons have the abbreviation (HC).
Hydrocarbons are gasoline vapors or raw gasoline itself. One reason
hydrocarbon emissions must be controlled is because it is one of the
major components of photochemical smog. Photochemical or "Los Angeles"
smog forms when hydrocarbons and oxides of nitrogen combine in the presence
of sunlight. In order to avoid this smog condition the hydrocarbon emis-
sions from automobiles must be controlled. Hydrocarbons also act as an
irritant to our eyes and some are suspected of causing cancer and other
health problems.
CARBON MONOXIDE
Another product of combustion that must be controlled is carbon monoxide.
Carbon monoxide has the abbreviation (CO). CO is also hazardous to our
health when it is mixed with the air we breathe. It can cause headaches,
reduce mental alertness and even cause death if enough of it is in the
air. Carbon monoxide is also a problem in that it speeds the formation
of photochemical smog. For these reasons CO emissions must be controlled.
1-1
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1-2
OXIDES OF NITROGEN
Oxides of nitrogen are the last harmful products of combustion we will
discuss. Nitrogen oxides have been given the abbreviation (NO ). As
you already know, oxides of nitrogen and hydrocarbons combine to form
photochemical smog. The sunlight which triggers the formation of photo-
chemical smog has another effect on oxides of nitrogen. Some of the
oxides of nitrogen are broken down and a gas called ozone is formed.
Ozone is a lung and eye irritant and it also deteriorates rubber and
affects the growth of vegetation. Since the nitrogen oxides have these
effects they must also be controlled.
Now that you are familiar with the emissions which must be controlled
let's find out where they originate.
FORMATION OF HYDROCARBONS
Hydrocarbons, you will recall, are fuel vapors or raw fuel. For this
reason hydrocarbon emissions will result from any uncontained supply
of gasoline. Hydrocarbon emissions also come from the tailpipe. If
the automobile engine could achieve "complete combustion," all of the
unburned fuel or hydrocarbons would be used up. However, it is impos-
sible for today's automobile engines to achieve "complete combustion."
Any time the fuel mixture in the combustion chamber is not completely
burned, some hydrocarbons will be emitted from the tailpipe. The two
main reasons why hydrocarbons are not completely burned are because of
engine misfire and "quench areas." When an engine misfire occurs, none
of the raw fuel or hydrocarbons are burned. When this happens they are
simply exhausted directly to the atmosphere. Quench areas are places in
the combustion chamber where the flame goes out before the fuel is com-
pletely burned. Small cavities such as where the head gasket seals the
cylinder head to the block is a quench area. Another quench area is
located between the top of the piston and the first compression ring.
These areas are sources of hydrocarbon emissions.
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1-3
FORMATION OF CARBON MONOXIDE
Carbon monoxide is partially burned fuel. Carbon monoxide is formed in
the combustion chamber whenever there is not enough air to burn all the
fuel. This means that whenever a "rich" air/fuel mixture is pulled into
the combustion chamber carbon monoxide will be formed. After the flame
goes out the carbon monoxide is exhausted through the tailpipe and into
the air.
FORMATION OF OXIDES OF NITROGEN
Oxides of nitrogen are also formed in the combustion chamber. These
oxides result from the nitrogen which is contained in our air. In some
cases combustion temperatures in the automobile engine can exceed 4500°F.
At temperatures above approximately 2500°F, nitrogen oxides will start
forming. Therefore, if combustion chamber temperatures exceed 2500°F,
oxides of nitrogen will be produced and then exhausted to our atmosphere.
Now that you understand how these emissions are formed in the automobile
engine, we will see how changes in ignition timing and carburetor adjust-
ment affect the amount of these pollutants.
As you know, changes in timing and carburet!on can have a large effect on
how an engine performs. These changes in timing and carburetion also can
have drastic effects on the amount of pollutants which are present in the
automobile's exhaust. The amount of hydrocarbons, carbon monoxide and
oxides of nitrogen which are present in the exhaust gases will vary as
timing and carburetion adjustments are changed.
IGNITION TIMING
Prior to emissions controlled automobiles, advancing the spark timing
was a common practice. Setting the spark timing this way caused the
spark plug to fire before the piston reached top dead center. This
advanced spark timing allowed the maximum amount of heat energy to be
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1-4
exerted on the piston. As a result the best performance and fuel econ-
omy could be obtained. Unfortunately, this also produced high hydrocarbon
and nitrogen oxide emissions levels.
In order to reduce emissions levels, ignition spark timing was retarded.
By firing the spark plug after the piston reaches top dead center, not
as much of the heat energy is converted to work on the piston. The
extra heat energy which is not used on the piston now passes through
the exhaust valve and into the exhaust manifold. This keeps the exhaust
gas temperatures higher. These higher exhaust temperatures allow burning
of the air/fuel mixture to continue in the exhaust manifold. This further
oxidation or burning in the exhaust manifold helps to reduce HC and CO
emissions.
Another advantage of retarded timing from an emissions standpoint is
that combustion temperatures are not as high. This is due to the fact
that the maximum combustion pressure will be lower. Since the combustion
temperatures will be lower and the formation of oxides of nitrogen de-
pends on temperature, a smaller amount of these pollutants will be ex-
hausted to the atmosphere.
There is one more advantage to using retarded spark timing. As you know,
when ignition timing is retarded the engine's idle speed will drop. This
decrease in idle speed occurs because less heat energy is applied to the
combustion chamber and more heat energy is being supplied to continue the
burning process in the exhaust manifold. In order to regain an acceptable
idle speed, the throttle plates must be opened wider. This wider throttle
plate opening allows more air to pass through the carburetor. This increase
in air flow will reduce the amount of residual exhaust gases in the cylinder.
This in turn will allow a more burnable mixture which can be made leaner.
Since the mixture can be leaner there will be more air in the combustion
chamber. As you know, the more air that is made available during com-
bustion the lower will b© the HC and CO emissions.
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1-5
CARBURETION
Adjustments made to the carburetor air/fuel ratio can also have a large
effect on the amount of pollutants which come from the automobile engine.
When idle mixture settings become richer there is less air present for
the combustion process. This lack of air results in an increase in hydro-
carbon and carbon monoxide emissions.
When the idle mixture screws are turned in, the amount of fuel is reduced
and the mixture becomes leaner. This leaner mixture contains more air
and therefore more oxygen is available for more complete burning of the
fuel. This results in lower HC and CO emissions levels.
As the idle mixture screws are turned in, the idle air/fuel mixture be-
comes leaner. If this mixture becomes too lean a "lean misfire" will
occur. A "lean misfire" will occur because the fuel is so diluted or
thinned out by the air that the mixture will not ignite. This leads to
a very large increase in hydrocarbon emissions. This happens because
the failure of the mixture to ignite results in that amount of raw fuel
being emitted to the atmosphere.
The carbon monoxide emissions decrease when a lean misfire condition is
present. Carbon monoxide is partially burned fuel. Since no combustion
takes place during a lean misfire condition no CO is formed and the total
amount of CO produced by the engine will be less.
A lean misfire usually occurs in one or more cylinders. This condition
may also move from cylinder to cylinder while the engine is running.
This is caused by the uneven distribution of the air/fuel mixture
delivered to each cylinder. This condition occurs mainly because of
problems with intake manifold design.
Now you should understand how changes in timing and carburetion adjust-
ment can'affect emissions levels. With this knowledge you will be able
to understand how each emissions control system we will discuss helps to
reduce the air pollution caused by the automobile.
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PCV
1-7
SYSTEM INTRODUCTION
The first automotive emissions control system we will discuss is the
positive crankcase ventilation system. The positive crankcase venti-
lation system, abbreviated PCV system, was developed because automobile
engines need to be ventilated. An engine's crankcase must be ventilated
if the engine is to operate properly. The crankcase must be ventilated
because of a harmful gas known as blowby.
FIGURE 1-1
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1-8
Blowby Is the name given to those combustion chamber gases which are
forced past the piston rings. Blowby occurs any time the engine is
running. Gases will be forced past the piston rings whenever a high
pressure condition is present in the combustion chamber. This high
pressure will exist during the compression stroke and the power stroke.
During engine operation harmful pollutants known as blowby gases are
forced into the crankcase.
When the engine is idling only a small amount of air and fuel is drawn
into the combustion chamber. This will result in family low pressures
in the combustion chamber. Also at idle the pistons are moving slowly
and the combustion and power strokes are not occuring as frequently as
at higher engine speeds. For these two reasons the amount of blowby
gases produced at idle is small. During high speed engine operation
more air and fuel is being drawn into the combustion chamber. The
power and compression strokes are occuring more frequently during high
speed operation. For these two reasons the amount of blowby gases
being produced is high. According to the operating conditions of the
engine only a small amount of blowby will be present during idle and
a larger amount at higher engine speeds.
Blowby gases contain gasoline vapor. These gasoline vapors contain
mostly hydrocarbons. It has been found, as you will recall from the
introduction, that HC and NO will combine in the presence of sunlight
A
to form what is known as photochemical smog.
In addition to gasoline vapors, blowby gases contain corrosive acids
and water vapor. If these blowby gases remain in the crankcase, engine
corrosion, oil dilution, and engine deposits or sludge will result.
Before 1960 the road draft tube was used to remove blowby gases from
the crankcase. This method of removing blowby gases resulted in a
cleaner, longer lasting engine.
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PCV
1-9
ROAD DRAFT TUBE
OPEN
BREATHER
CAP
DRAFT
TUBE
BLOW-BY
GASES
) AIR
FLOW
FIGURE 1-2
The road draft tube was connected to the crankcase at one end and the
other end extended into the air stream below the automobile. An open
oil filler cap was also used with this method of crankcase ventilation.
As outside air flowed past the open end of the draft tube a slight
vacuum was created. This vacuum would draw fresh air through the open
oil filler cap, then through the crankcase and finally out the road
draft tube. As the air passed through the crankcase it would pick up
the blowby gases and remove them to the atmosphere. Since the vacuum
created at the end of the road draft tube was dependent on automobile
speed, this type of crankcase ventilation was not effective at speeds
below 25 MPH.
It was found that 20% of all hydrocarbon emissions came from the crank-
case. These hydrocarbon emissions could be eliminated if the blowby
gases were not discharged to the atmosphere.
On most California automobiles manufactured in 1961 and most U.S. auto-
mobiles manufactured after 1962 the road draft tube was replaced by a
new crankcase ventilation system. This new system was called the
Positive Crankcase Ventilation System. Most people call it the PCV
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1-10
system. This system of crankcase ventilation circulates fresh air
through the crankcase and carries the blowby gases into the intake mani-
fold or air cleaner. Blowby is then drawn into the combustion chambers
and burned with the air/fuel mixture. The system is called "Positive
Crankcase Ventilation" because air is always circulated through the
crankcase whenever the engine is running.
1. Whenever the engine is operating, blowby gases will be
forced into the
2. The gasoline vapors which are contained in the blowby
gases contain mostly .
3. Hydrocarbon emissions must be controlled since they
combine with NO in the presence of sunlight to form
smog.
4. Blowby gases contain gasoline vapors, corrosive acids and
vapor.
5. Before approximately 1960, a device was used to remove
the blowby gases from the crankcase to the atmosphere.
This device was called a
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PCV
1-11
6. Beginning in 1961 and used on nearly all automobiles
manufactured after 1963, was a new crankcase ventilation
system. This system is called the
system.
7. This new crankcase ventilation system has been abbrevia-
ted and called the system.
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PCV
1-13
SYSTEM/COMPONENT PURPOSE
You will recall from the introduction, the PCV system provides constant
ventilation of the engine crankcase. Blowby gases contain the harmful
pollutant known as HC or hydrocarbons. You will also remember that these
blowby gases must be removed from the crankcase. The PCV system directs
the blowby gases to the intake manifold or air cleaner for burning in the
combustion chamber. The purpose of the PCV system is to constantly
ventilate the engine crankcase and to prevent hydrocarbons from escaping
to the atmosphere.
TYPE ONE PCV SYSTEM
There are four major types of PCV systems. The Type 1 system or "open"
PCV system was used on most cars between 1961 and 1968. This system is
called an open system because the breather cap leaves the crankcase
open to the atmosphere. As can be seen in figure 1-3, the Type 1 or
TYPE I SYSTEM (OPEN)
CONNECT
HOSE
PCV VALVE
OPEN
BREATHER
CAP
OUTSIDE
AIR
FIGURE 1-3
"open" PCV system has three major components. An open oil breather cap,
a PCV valve and a connecting hose are used with Type 1 systems.
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1-14
OPEN OIL BREATHER CAP
The open oil breather cap used in this system serves as an open vent to
allow air Into the crankcase. This allows the crankcase to breathe,
thus the name breather cap. During high speed, wide-open throttle
operation , the Intake manifold vacuum Is low, crankcase pressures are
high, and excessive blowby gases are produced. Under these conditions
the PCV system may be unable to remove all the blowby gases. When this
happens the breather cap will serve as an additional vent for the blowby
gases to escape from the crankcase.
PCV VALVE
The PCV valve serves as the control unit for the crankcase ventilation
system. Due to the changes in throttle opening during engine operation,
the intake manifold vacuum will vary. If no valve was used with this
change in vacuum, an unwanted variation in crankcase ventilation would
occur. For this reason a regulating valve named the PCV valve has been
used.
During Idle operation, when intake manifold vacuum 1s high and the blowby
gases being produced are quite small, only a small flow of air through
the crankcase is desired. As engine speed increases to a higher speed
and manifold vacuum drops, the blowby gases being produced will increase
to a maximum. With these conditions a high amount of air flow through
the crankcase is desired to remove the large amount of blowby gases. The
PCV valve's purpose is to regulate the air flow through the crankcase
according to these conditions.
CONNECTING HOSE
The final component of the Type 1 PCV system is the connecting hose.
This hose Is the link between the crankcase and the intake manifold.
The PCV valve is usually located at one end of this hose.
TYPE TWO PCV SYSTEM
The Type 2 PCV system is much the same as the Type 1 system. This system
was Installed on some 1950 and early 1960 California cars which were not
originally equipped with a PCV system. This system also has three major
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PCV
1-15
components. A restricted oil breather cap, a West Coast Control Valve
and a connecting hose are used.
WEST COAST
CONTROL
VALVE
TYPE II SYSTEM
HOSE
INTAKE
MANIFOLD
RESTRICT-
ED
BREATHER
CAP
OUTSIDE
AIR
BLOW-BY
GASES
FIGURE 1-4
It may be seen in figure 1-4 that these components are connected in the
same manner as those in the Type 1 PCV system. The purpose of these
components is also much the same as those in the Type 1 system.
RESTRICTED OIL BREATHER CAP
The restricted oil filler cap serves the purpose of a vent to allow
fresh air into the crankcase. It also provides a resistance to air flow
to prevent blowby gases from moving out of the crankcase to the
atmosphere.
WEST COAST CONTROL VALVE
The West Coast Control Valve's purpose is exactly the same as the PCV
valve's purpose. It regulates the amount of air flow through the crank-
case. This valve will allow a high rate of flow through the crankcase
when an excessive blowby condition is present. When only small amounts
of blowby are present in the crankcase the valve will permit only a
small amount of air flow through the system.
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1-16
CONNECTING HOSE
The last component in the Type 2 system is the connecting hose. This hose
serves to link the crankcase to the intake manifold. As with the PCV
valve, the West Coast Control Valve will be located at one end of this hose.
8. There are major types of PCV systems.
9. The PCV system's purpose is to constantly ventilate the
engine crankcase and to prevent
emissions.
10. There are three components in the Type 1 PCV system.
The most important component is the
which regulates the amount of crankcase ventilation.
TYPE THREE PCV SYSTEM
The Type 3 PCV system is different from the first two systems discussed
since it doesn't use a regulating valve. This system actually has only
one component. A connecting hose runs from the crankcase to the air
cleaner snorkel. This may be seen in figure 1-5. The purpose of this
connecting hose is to link the crankcase to the air cleaner to provide
a means for the blowby gases to escape from the crankcase. No component
is used in this system to allow fresh air to enter the system.
The purpose of the Type 3 PCV system is to vent the harmful blowby gases
from the crankcase. This system has been discontinued by American
manufacturers but still may be found on a few foreign models.
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PCV
1-17
HOSE
TYPE III SYSTEM
(NO PCV VALVE USED)
SEALED
BREATHER
CAP
BLOW-BY
GASES
FIGURE 1-5
TYPE FOUR PCV SYSTEM
The Type 4 or "closed" PCV system is the system which has been used on
all American automobiles since 1968. This system is called the "closed"
system because the oil breather cap is closed off from the atmosphere.
The components of this Type 4 system are the same as the Type 1 system
with the exception of the oil breather cap.
HOSE
PCV VALVE
TYPE IV SYSTEM
(CLOSED SYSTEM) nf~u
./-FRESH
^^••"^•"J • M%4^^»
AIR
HOSE
BLOW-BY GASES
FIGURE 1-6
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1-18
As you can see in figure 2-6, this system has a PCV valve, connecting
hose, and a closed oil breather cap. The purpose of the valve and
connecting hose is just the same as those used in the Type 1 system.
You may even consider the Type 4 system as a Type 1 system with the
addition of a new breather cap. This closed breather cap has a small
connecting hose built into it. This hose connects to the air cleaner at
its other end.
CLOSED OIL BREATHER CAP
You will remember that under hard acceleration the large amount of
blowby gases produced may niove from the crankcase through the breather
cap as well as the PCV valve and connecting hose. With the use of the
closed breather cap these blowby gases will pass through the small hose
which connects to the air cleaner.
The purpose of the closed breather cap is to direct these extra gases to
the air supply where they too can be burned in the combustion chamber.
This allows the Type 4 or "closed" PCV system to ventilate the blowby
gases from the crankcase and feed them back to the engine under all
conditions. Now no blowby gases are allowed into the atmosphere. With
the use of this closed system the entire HC emissions contributed by
the crankcase have been eliminated.
11. The Type 4 PCV system uses a oil breather
cap.
12. NO regulating valve is used in the Type PCV system.
13. The PCV system eliminates all the hydrocar-
bon emissions from the crankcase.
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PCV
1-19
SYSTEM/COMPONENT FUNCTION
You will recall from the last section that the Type 1 PCV system has
three components. The most important component 1s the PCV valve Itself.
Now you will learn how and when this component works.
TYPE ONE PCV VALVE
The PCV valve 1s made up of the body, a spring, and the plunger or valve.
It also has an opening at one end to be connected to the crankcase. The
opening at the other end connects to the Intake manifold connecting hose.
The parts of the PCV valve may be seen in figure 1-7.
POSITIVE CRANMCASE VENTLATON VALVE
* ~?
NTAKE
MAMFOLD
PLUNGER
OR VALVE
FIGURE 1-7
When the engine 1s operating intake manifold vacuum pulls the plunger
against the spring. This will move the plunger toward the intake mani-
fold end of the PCV valve body. The amount of plunger movement will
change with any change in intake manifold vacuum. The higher the Intake
manifold vacuum, the more the plunger will move against the spring.
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1-20
ENGINE OFF OR BACKFIRE
POSITIVE CRANKCASE VENTILATION VALVE
(PCV)
VALVE BOOT
/
r
INTAKE
MANIFOLD
SIDE
PLUNGER
OR VALVE
CRANKCASE
SIDE
FIGURE 1-8
As you can see in figure 1-8, when the engine is not running there is no
intake vacuum. With this condition the spring pushes the plunger to the
crankcase end of the valve body. The plunger will seat against the valve
body and prevent any air flow through the PCV valve. The plunger will
also move to this position if the engine should backfire through the
carburetor. This high pressure which results from the backfire will
overcome the pressure caused by the blowby gases and seat the plunger in
this position. This prevents the flame from moving into the crankcase
and igniting the blowby gases.
IDLE OR LOW SPEED
When the engine is idling intake manifold vacuum will increase to a high
value. This will pull the plunger to the intake manifold end of the
valve. In this position the plunger will seat against the valve body.
The air which is drawn through the crankcase will have to pass through
the small idle grooves which are cut into the plunger. Since these
grooves provide the only passages for air movement the amount of air
circulating through the crankcase is small. You will remember that at
idle only a very small amount of blowby gases are being produced.
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PCV
1-21
IDLING OR LOW SPEED
,N*U-VE BODY
SPRING
PLUNGER
OR VALVE
(FORWARD POSITION)
FIGURE 1-9
For this reason, only a small amount of air circulation through the crank-
case is needed. This amount of air circulation will be set by the size
and number of idle grooves cut into the plunger.
HIGHER SPEED
When the engine is accelerated to a cruise speed, intake manifold vacuum
will decrease. With this condition the spring will push the plunger to
HIGHER SPEED
VALVE
SPRING
PLUNGER
OR VALVE
(MIDDLE POSITION)
FIGURE 1-10
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1-22
a position in the middle of the valve body. As you can see in figure
1-10, this plunger position will allow a maximum flow of air through the
crankcase. You will recall that a large amount of blowby gases are
produced under these conditions. The PCV valve will allow the correct
amount of air flow through the crankcase to remove this large amount of
blowby.
Now you should understand the function of the PCV valve and how it regu-
lates the air flow through the crankcase.
14. A PCV valve is composed of the valve body, a spring, and
the
15. A amount of crankcase ventilation is desired
during periods of high engine speed.
16. Whenever the engine is operating at low speeds, a
amount of crankcase ventilation is desired.
TYPE TWO WEST COAST CONTROL VALVE
The Type 2 crankcase ventilation system uses a West Coast Control Valve
instead of a PCV valve. This control valve is the major component in
this Type 2 system. As you can see in figure 1-11, this West Coast
Control Valve is made of several parts. The valve body has an opening
which is connected to the intake manifold. This valve body also has a
small breather hole to allow atmospheric pressure into the valve. Inside
the valve body is a diaphragm, modulator ball, and modulator spring.
-------
WEST COAST CONTROL VALVE
VALVE BODY
DIAPHRAGM
BREATHER
HOLE
MODULATOR
^SPRING
TO INTAKE
MANIFOLD
IDLE GROOVE
MODULATOR BALL
MODULATOR BALL
SEAT
FROM VALVE COVER
PCV
1-23
FIGURE 1-11
This system also uses a special restricted oil breather cap which plays
an important role in the operation of the system. When the engine is
off and no intake manifold vacuum is present the modulator spring will
hold the diaphragm and modulator ball away from the modulator ball seat
located near the intake manifold connection.
IDLE OR LOW SPEED
When the engine is started and allowed to idle the manifold vacuum will
increase to a high value. This vacuum will draw air through the re-
stricted oil filler cap. Due to this restriction and the presence of
intake manifold vacuum, a crankcase vacuum will be created. This crank-
case vacuum will act upon the diaphragm pulling it against spring
pressure toward the modulator ball seat. When a high manifold vacuum
is present the crankcase vacuum will also be high. This will pull the
diaphragm against spring pressure until the modulator ball seats. In
this position, as seen in figure 1-12, the air circulating through the
crankcase must pass through the oil cap, then through the crankcase, and
then through the small idle groove which is cut into the modulator ball.
The ventilating air, containing the blowby gases, then passes into the
intake manifold and into the combustion chamber for burning.
-------
1-24
DIAPHRAGM
WEST COAST CONTROL VALVE AT IDLE
^ VfcLVE BODY
flNS^X^ /MODULATOR
IL 3h Xs"*16
' TO INTAKE
MANIFOLD
BREATHER
HOLE
BLOW-BY
GASES
THROUGH
DLE GROOVE
\
SEAT
MODLATOR BALL
SEATED
FROM VALVE COVER
[BLOW-BY GASES)
FIGURE 1-12
HIGHER SPEED
When the engine speed is increased to a cruise condition the intake
manifold vacuum will drop. This will cause a drop in crankcase vacuum.
As you can see in figure 1-13, this drop in crankcase vacuum allows the
modulator spring to push the modulator ball off its seat. This will
WEST COAST CONTROL VALVE AT CRUISE
VALVE BODY
DIAPHRAGM
BREATHER
HOLE
MODULATOR
SPRING
TO INTAKE
MANFOLD
^-MODULATOR BALL
OFF SEAT
FROM VALVE COVER
(BLOW-BY GASES)
Figure 1-13
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PCV
1-25
increase the effective opening between the intake manifold and the
crankcase allowing a greater amount of crankcase ventilation.
The West Coast Control Valve will vary the amount of crankcase ventilation
over a very wide range of driving conditions. This will allow the blowby
gases to be vented from the crankcase only at the rate required. This in
turn will prevent any excessive leaning of the air/fuel mixture entering
the carburetor.
17. The West Coast Control Valve regulates the amount of
crankcase
18. The West Coast Control Valve will allow a
amount of ventilation at high engine speeds.
19. At low engine speeds the amount of ventilation will be
restricted. The blowby gases will pass through the idle
which is cut into the modulator ball.
TYPE THREE PCV SYSTEM
The Type 3 system, you will recall, has only one hose which links the
crankcase to the air cleaner. As you can see in figure 1-14, the blowby
gases, which are escaping from the combustion chamber past the piston
rings, create a slight pressure in the crankcase. Inside the air cleaner
a.slight vacuum condition is present. These two conditions, pressure in
the crankcase and vacuum in the air cleaner, will act together to venti-
late the crankcase. The blowby gases will move through the crankcase
until the vacuum-in the hose draws them into the air cleaner for burning
•
in the combustion chamber.
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1-26
TYPE III SYSTEM
(NO PCV VALVE USED)
HOSE
SEALED
BREATHER
CAP
BLOW-BY
GASES
FIGURE 1-14
TYPE FOUR PCV SYSTEM
The Type 4 PCV system functions exactly the same as the Type 1 system.
The PCV valve function will be briefly reviewed.
ENGINE OFF OR BACKFIRE
When the engine is off or a backfire through the carburetor has occurred
the valve will be positioned as in figure 1-15. In this position the
crankcase and the intake manifold will be closed from each other.
ENGNE OFF OR BACKFRE
VALVE BODY
SPRMG
PLUNGER
OR VALVE
(BACK POSITION)
FIGURE 1-15
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PCV
1-27
IDLE OR LOW SPEED
When the intake manifold vacuum is high, such as at idle, low speedor decel-
eration, the plunger will position itself as figure 1-16. This position
will provide a limited amount of crankcase ventilation. Youwill recall that
under, these engine conditions only a small amount of blowby is produced.
IDLING OR LOW SPEED
,-VALVE BODY
SPRING
PLUNGER
OR VALVE
(FORWARD POSITION)
FIGURE 1-16
HIGHER SPEED
When engine manifold vacuum decreases during higher engine speed opera-
tion, the plunger will move to the position seen in figure 1-17.
HIGHER SPEED
VALVE
SPRWG
PLUNGER
OR VALVE
(MIDDLE POSITION)
FIGURE 1-17
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1-28
This will allow a maximum amount of crankcase ventilation to remove the
large amount of blowby gases being produced.
20. Whenever the engine is operating, intake manifold vacuum
will pull the plunger or valve against
pressure.
21. The higher the intake manifold vacuum the more the
plunger will move toward the
end of the valve body.
22. As the plunger moves toward the intake manifold end of
the valve body the amount of crankcase ventilation will
be
23. Intake manifold vacuum increases to a high value when
the engine is idling. This will pull the plunger to the
intake manifold end of the valve. When the plunger is
in this position, it will seat against the valve body.
The air which is circulated through the crankcase will
have to pass through which are cut into
the plunger.
CLOSED OIL BREATHER CAP
During periods of heavy acceleration the PCV valve will not provide
enough ventilation to remove all the blowby gases produced. In an
"open" system these excess gases will pass through the open oil breather
-------
PCV
1-29
cap to the atmosphere. The "closed" or Type 4 system, however, uses a
different oil filler cap.
The oil cap used on the Type 4 system has a hose connected to it. The
other end of this hose connects to the air cleaner.
TYPE IV SYSTEM
(CLOSED SYSTEM)
HOSE
PCV VALVE
SEALED
OIL DIP
STICK
FRESH AIR
HOSE
SEALED
OIL
FILLER
CAP
BLOW-BY GASES
FIGURE 1-18
This may be seen in figure 1-18. During periods of normal operation the
air needed to ventilate the crankcase is drawn from the air cleaner.
During heavy acceleration the excess blowby gases will leave the oil
breather cap through the connecting hose. These gases will now be
burned in the combustion chamber as they mix with the incoming air in
the air cleaner.
This system also has an additional filter in the air cleaner. A small
gauze inlet filter is positioned where the hose and the air cleaner body
meet. This may be seen in figure 1-19. This filter will clean the air
entering the crankcase during normal operation. It also prevents any oil
from entering the air cleaner during periods of heavy acceleration.
Now it should be easy to see how the "closed" or Type 4 PCV system can
eliminate all the hydrocarbon emissions from the crankcase.
-------
1-30
REMOVABLE INLET FILTER
AIR FILTER
MOUNTING
GROMET
HOSE TO
VALVE COVER
AIR
-CLEANER
SCREEN
METAL
FILTER
COVER
CONTAINS
FILTER
GAUZE
SOME MANUFACTURERS REQUIRE
REPLACEMENT OF CRANKCASE INLET
FILTER EVERY 6,000 MILES
OR 6 MONTHS
oo
00
00
oo
00
00
00
oo
AIR CLEANER
AM FILTER
FILTER/GAUZE \ \
INLET FILTER V
CRANKCASE VENT
HOSE TO VALVE COVER
FIGURE 1-19
24. The Type 4 PCV system uses an additional filter located
in the
-------
PCV
1-31
25. The closed is used to
capture the excess blowby created during heavy engine
acceleration.
-------
PCV
1-33
SYSTEM INSPECTION
An Inspection of the PCV system should be made periodically and prior to
any testing of the system. This inspection will require no tools or
instruments and takes only a few minutes. Many problems may be avoided
or corrected by these steps.
1. Check to see that all components are properly installed on
the engine and no modifications have been made. Air cleaner,
oil breather cap, PCV valve and all hoses should be in place.
In order for the PCV system to function as it was designed
all components must be installed correctly. The air cleaner
must be sealed and have no modifications and connecting hoses
must be in place. The efficiency of the system will be
reduced if any of these parts are missing.
2. Inspect all filters in the system. Air cleaner filter, oil
breather cap filter, and the air inlet filter should all be
inspected. If any of these are excessively dirty, clean or
replace the filter.
Excessive dirt in a filter will restrict air flow through the
system. In order for the PCV system to operate efficiently
no unnecessary restriction to air flow can be allowed.
3. Check the system connecting hoses for cracks, deterioration,
and loose connections.
Any air leaks into the system will reduce the PCV system's
effectiveness. This condition may also lean out the air/fuel
ratio delivered to the engine. Decayed or cracked hoses and
hoses with loose connections will allow unwanted air into the
system.
-------
1-34
4. Check to see if any large crankcase oil leaks are present
in the engine.
A large crankcase oil leak will decrease the ventilation
through the crankcase. This condition if very severe may
also indicate a restriction somewhere in the system.
However, caution must be taken not to confuse this type
leak with an oil pressure or main seal leak. A crankcase
restriction would most likely be caused by a blocked PCV
valve.
5. Last, a check of the air cleaner and air inlet filter should
be made to see if excessive oil is present.
This condition will also show a possible blocked PCV valve.
Under this condition all blowby will escape from the crank-
case through the air inlet tube. This will leave oil in
the air inlet filter and air cleaner body.
26. Any large crankcase oil leak will cause a
in the ventilation through the crankcase.
27. The most probable cause of poor crankcase ventilation
would be a blocked
-------
PCV
1-35
SYSTEM TESTING
The PCV system should be tested periodically or anytime it is suspected
of working improperly. Testing this system is relatively simple and
requires little time to complete. Testing this system involves three
separate tests - the RPM drop test, the simple vacuum draw test, and the
vacuum draw test using an instrument.
RPM DROP TEST
The RPM drop test is the first test which should be done on the PCV
system. The only tool needed for this test is a tachometer.
First the tachometer is connected to the engine. Allow the engine to
reach normal operating temperature and record the engine speed or RPM.
Next the air flow through the PCV system should be completely blocked.
As can be seen in figure 1-20, this should be done by removing the PCV
40-80 RPM DROP WHEN PCV PLUGGED
FIGURE 1-20
valve from the crankcase and holding a finger over the open end of the
valve. Record the engine RPM with the PCV system plugged. The RPM should
be 40-80 RPM lower than when the PCV system is fully connected. If no
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1-36
drop in RPM is noted this is an indication of a blocked PCV system.
This could be a blocked valve, hoses, crankcase passages or intake
manifold passages.
VACUUM DRAW TEST 1
PCV VALVE
CORRECT
ADAPTER
BE SURE TESTER
IS VERTICAL
PCV
INCLINED RAMP
a BALL TESTER
PLACE OVER
OIL INLET
FIGURE 1-21
Next an instrument vacuum draw test should be conducted. This test
should be conducted in two stages. A test of the entire system should be
-------
PCV
1-37
made using either an adjustable PCV tester or an inclined ramp and ball
tester. The engine should be brought to normal operating temperature.
With the engine idling the tester should be placed over the oil filler
hole as seen in figure 1-21.
If a weak vacuum is indicated on the tester the PCV system is not opera-
ting properly. This may be caused by poor engine condition or a plugged
or malfunctioning PCV valve. To determine if the valve is operating
properly it should be tested separately from the crankcase. This can be
done using the adjustable PCV tester. Connecting the tester to the valve
as shown in figure 1-22 will give an indication of the valve's condition.
PCV VALVE
FIGURE 1-22
If the system test indicated a faulty system and the valve test indicated
a properly functioning valve the engine is in poor condition.
VACUUM DRAW TEST 2
If neither of these test instruments are available a simple vacuum draw
test may be performed. As with the previous test the engine is allowed
to reach normal operating temperature. With the engine idling, place a
piece of thin paper over the oil filler hole as shown in figure 1-23.
The presence of crankcase vacuum will be indicated by the paper being
drawn tight over the hole.
-------
1-38
OIL FILLER
HOLE
PCV
FIGURE 1-23
When doing any service or maintenance on the PCV system, it is important
to consult the manufacturer's specifications. Most manufacturers req^rtre
system inspection and valve replacement every 12,000 miles or 12 months.
Check a good service manual since some manufacturers use PCV valves which
last for up to 30,000 miles. In addition, all filters, oil caps, and
other related parts should be serviced, inspected or replaced, when
required by the manufacturer. In addition, specifications must be con-
sulted for installing the proper PCV valve. Exact part numbers must be
used when replacing PCV valves since many valves appear the same but
allow different amounts of air to pass through the valve. Special PCV
hose should always be used whenever this hose must be replaced, since the
wrong hose may collapse causing the system to malfunction. Proper
maintenance and servicing will assure that the PCV system continues to
function as it was designed.
The proper operation of the PCV system aids long engine life and the
reduction of hydrocarbon emissions.
-------
PCV
1-39
28. The first test which should be performed on the PCV
system is the drop test.
29. Whenever the PCV hose must be replaced, special PCV
hose should always be used since the wrong hose may
causing the system to malfunction.
30. A draw test should also be performed when
testing the PCV system.
31. The and air inlet filter require
scheduled replacement.
-------
PCV
1-41
SYSTEM SUMMARY
PURPOSE
The purpose of the PCV system is to reduce hydrocarbon emissions to the
atmosphere. It also helps prevent oil dilution and sludge formation in
the crankcase. This is done by directing blowby gases in the crankcase
back into the combustion chamber to be burned in the normal combustion
process.
MAIN COMPONENTS
Sealed Oil Filler Cap - Prevents escape of blowby gases to the atmosphere
from around the oil filler cap during heavy acceleration.
Sealed Dipstick Cap - Prevents escape of blowby gases to the atmosphere
from around the dipstick during heavy acceleration.
Air Intake Hose - Allows fresh air to enter the crankcase from the air
cleaner.
PCV Valve - Composed of body, plunger, and spring, the PCV valve meters
the flow of blowby gases from the crankcase back into the intake manifold
by sensing intake manifold vacuum.
SYSTEM FUNCTION
Intake manifold vacuum draws blowby gases from the crankcase into the
manifold to be consumed in the combustion chamber. The PCV valve plunger
prevents blowby gas flow during engine off or engine backfire conditions.
Blowby gas flow is regulated by the amount of intake manifold vacuum
acting on the PCV valve spring and plunger.
-------
PCV
1-43
ANSWERS
1. crankedse
2. hydrocarbons
3. photochemical
4. water
5. road draft tube
6. positive crankcase ventilation
7. PCV
8. four
9. hydrocarbon
10. PCV valve
11. closed
12. three
13. type four
14. valve or plunger
15. large
16. small
17. ventilation
18. large
19. groove
20. spring
21. intake manifold
22. reduced
23. grooves
24. air cleaner
25. oil breather cap
26. decrease
27. PCV valve
28. RPM
29. collapse
30. vacuum
31. PCV valve
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-450/3-77-036
2.
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
Motor Vehicle Emissions Control - Book One
Positive Crankcase Ventilation Systems
5. REPORT DATE
November 1977
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
B.D. Hayes
M.T. Maness
8. PERFORMING ORGANIZATION REPORT NO.
R.A. Ragazzi
R.A. Barrett
PERFORMING ORGANIZATION NAME AND ADDRESS
Department of Industrial Sciences
Colorado State University
Fort Collins, Colorado 80523
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
5008135-01-0
T900621-01-0
2. SPONSORING AGENCY NAME AND ADDRESS
Control Programs Development Division
Office of Air Quality Planning and Standards
Office of Air and Waste Management
U.S. Environmental Protection Agency
13. TY.PE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
EPA 200/04
5. SUPPLEMENTARY NOTES
Research Triangle Park, North Carolina 27711
6. ABSTRACT
This book is one of a series designed specifically to teach the concepts of auto-
mobile emissions control systems. It is intended to assist the practicing mechanic
or the home mechanic to better understand the Positive Crankcase Ventilation
Systems which are an integral part of automobiles today. The mechanic's increased
knowledge should help him keep "emissions controlled" vehicles operating as designed.
Respectable fuel economy, performance and driveability, as well as cleaner air, can
be obtained from the automobile engine that has all of its emissions systems
functioning properly.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Crankcase
Photochemical
Positive Crankcase
Ventilation
Hydrocarbons
Intake Manifold
System Inspectic
Carbon Monoxide
Oxides of Nitro-
gen
Ignition Timing
Carburetion
n
8. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
50
20. SECURITY CLASS (Thispage)
JL
22. PRICE
EPA Form 2220-1 (9-73)
.S. GOVERNMENT PRINTING OFFICE: 19 7 8 .7U 5 - 2 2«v
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