Smog Emissions Control Systems And Components –
Questions With Correct Solutions
Dilution and contamination of engine oil, the formation of oil sludge, and
pressure in the crankcase that could force oil past seals and gaskets are all
problems caused by... Right Ans - Blow-by vapors
What was the first method used to vent crankcase vapors? Right Ans -
Road draft tube
What was the main reason PCV systems were mandated on non-commercial
vehicles? Right Ans - Older systems vented directly to atmosphere,
contributing to air pollution
When did the first PCV systems appear on vehicles? Right Ans - 1950s
Before PCV systems were mandated, what percentage of vehicle emissions
were from crankcase vapors? Right Ans - 20%
When did California start requiring PCV systems on passenger cars? Right
Ans - 1961
When did Federal regulations require PCV systems on cars? Right Ans -
1963
What does the PCV system do? Right Ans - Routes crankcase gases to the
intake system where they are drawn into the combustion chamber and
burned
As engine vacuum drops, what opens the PCV valve? Right Ans - Spring
tension
What two types of PCV system have been used in the industry? Right Ans -
Open and closed
When the breather that allows air into the crankcase is vented to atmosphere,
the system is considered... Right Ans - Open
,When the breather that allows air into the crankcase is connected to the air
cleaner, the system is considered... Right Ans - Closed
Under full-throttle conditions, crankcase pressures... while vacuum levels...
Right Ans - Build up; drop
Federal legislation was passed requiring closed PCV systems in what year?
Right Ans - 1968
Closed PCV systems were required as of what vehicle model year? Right
Ans - 1969
In a closed PCV system, excessive fumes are forced out the breather, then...
Right Ans - Through the air cleaner, carburetor, then into the engine
When an engine is at idle, the vacuum signal to the PCV valve is... Right Ans
- High
What is the PCV valve's operating condition when the engine is at idle?
Right Ans - The high vacuum signal overcomes spring pressure to open the
valve
What happens to manifold vacuum as engine speed increases? Right Ans -
The vacuum level drops
What is the operating condition of the PCV valve at cruise? Right Ans -
Spring pressure changes the valve opening to allow full flow
What happens to manifold vacuum at full throttle? Right Ans - Vacuum
drops to zero
What is the operating condition of the PCV valve during full throttle? Right
Ans - Spring pressure closes the PCV valve
Instead of a PCV valve, some engines use a carefully sized... Right Ans -
Orifice
At what intervals should PCV systems be checked? Right Ans - Between
12,000 and 30,000 miles
, The PCV system should be checked whenever these signs of a ventilation
problem occur: Right Ans - Stalling and rough idling
During testing of the PCV valve, what should happen to engine RPM when you
pinch off the ventilation tube between the vacuum source and the PCV valve?
Right Ans - Engine speed should drop by 50 RPM or more
With the engine idling, what should the technician observe when
disconnecting the PCV valve? Right Ans - A hissing noise should be heard as
air passes through the valve, and strong vacuum should be felt when a finger
is placed over the valve inlet
With the engine running at idle, remove the crankcase breather or oil filler
cap. Loosely hold a piece of stiff paper over the opening. What should happen
within 60 seconds if the PCV system is functioning properly? Right Ans -
The paper should be sucked against the opening
Stop the engine and remove the PCV valve. Shake the valve. What should you
observe? Right Ans - A clicking or ratting noise should be heard
When testing the PCV system using a water manometer connected to the oil
dipstick tube, how much vacuum should be measured? Right Ans - 7-14 in
H2O (0.5-1.0 in Hg)
PCV systems are normally trouble-free, but they should be checked at
intervals, and maintained in the following ways: Right Ans - A stuck valve
should be replaced; hoses should be cleaned
Route PCV hoses so they do not get... Right Ans - Kinked or burned
If PCV hoses become dirty, you can... Right Ans - Blow them out with
compressed air
Most manufacturers recommend that PCV valves be... rather than... Right
Ans - Replaced; cleaned
Questions With Correct Solutions
Dilution and contamination of engine oil, the formation of oil sludge, and
pressure in the crankcase that could force oil past seals and gaskets are all
problems caused by... Right Ans - Blow-by vapors
What was the first method used to vent crankcase vapors? Right Ans -
Road draft tube
What was the main reason PCV systems were mandated on non-commercial
vehicles? Right Ans - Older systems vented directly to atmosphere,
contributing to air pollution
When did the first PCV systems appear on vehicles? Right Ans - 1950s
Before PCV systems were mandated, what percentage of vehicle emissions
were from crankcase vapors? Right Ans - 20%
When did California start requiring PCV systems on passenger cars? Right
Ans - 1961
When did Federal regulations require PCV systems on cars? Right Ans -
1963
What does the PCV system do? Right Ans - Routes crankcase gases to the
intake system where they are drawn into the combustion chamber and
burned
As engine vacuum drops, what opens the PCV valve? Right Ans - Spring
tension
What two types of PCV system have been used in the industry? Right Ans -
Open and closed
When the breather that allows air into the crankcase is vented to atmosphere,
the system is considered... Right Ans - Open
,When the breather that allows air into the crankcase is connected to the air
cleaner, the system is considered... Right Ans - Closed
Under full-throttle conditions, crankcase pressures... while vacuum levels...
Right Ans - Build up; drop
Federal legislation was passed requiring closed PCV systems in what year?
Right Ans - 1968
Closed PCV systems were required as of what vehicle model year? Right
Ans - 1969
In a closed PCV system, excessive fumes are forced out the breather, then...
Right Ans - Through the air cleaner, carburetor, then into the engine
When an engine is at idle, the vacuum signal to the PCV valve is... Right Ans
- High
What is the PCV valve's operating condition when the engine is at idle?
Right Ans - The high vacuum signal overcomes spring pressure to open the
valve
What happens to manifold vacuum as engine speed increases? Right Ans -
The vacuum level drops
What is the operating condition of the PCV valve at cruise? Right Ans -
Spring pressure changes the valve opening to allow full flow
What happens to manifold vacuum at full throttle? Right Ans - Vacuum
drops to zero
What is the operating condition of the PCV valve during full throttle? Right
Ans - Spring pressure closes the PCV valve
Instead of a PCV valve, some engines use a carefully sized... Right Ans -
Orifice
At what intervals should PCV systems be checked? Right Ans - Between
12,000 and 30,000 miles
, The PCV system should be checked whenever these signs of a ventilation
problem occur: Right Ans - Stalling and rough idling
During testing of the PCV valve, what should happen to engine RPM when you
pinch off the ventilation tube between the vacuum source and the PCV valve?
Right Ans - Engine speed should drop by 50 RPM or more
With the engine idling, what should the technician observe when
disconnecting the PCV valve? Right Ans - A hissing noise should be heard as
air passes through the valve, and strong vacuum should be felt when a finger
is placed over the valve inlet
With the engine running at idle, remove the crankcase breather or oil filler
cap. Loosely hold a piece of stiff paper over the opening. What should happen
within 60 seconds if the PCV system is functioning properly? Right Ans -
The paper should be sucked against the opening
Stop the engine and remove the PCV valve. Shake the valve. What should you
observe? Right Ans - A clicking or ratting noise should be heard
When testing the PCV system using a water manometer connected to the oil
dipstick tube, how much vacuum should be measured? Right Ans - 7-14 in
H2O (0.5-1.0 in Hg)
PCV systems are normally trouble-free, but they should be checked at
intervals, and maintained in the following ways: Right Ans - A stuck valve
should be replaced; hoses should be cleaned
Route PCV hoses so they do not get... Right Ans - Kinked or burned
If PCV hoses become dirty, you can... Right Ans - Blow them out with
compressed air
Most manufacturers recommend that PCV valves be... rather than... Right
Ans - Replaced; cleaned
