The major causes of air pollution are industry and
contain water in suspension. This water, trapped in the
the gasoline engine. As an AS, you are directly con-
muffler, will gradually rust it. With every gallon of
cerned with the prevention of pollution by the gasoline
gasoline that is burned, approximately 6.9 pounds of
engine and its fuel system. To help reach this goal, you
water are formed, and pass through the muffler. Much
need to know what these polluting substances
of this moisture will remain in the muffler if the vehicle
(emissions) are, where in the gasoline engine and fuel
is driven only short distances, but most of it will be
system they originate, how they are controlled, and how
expelled if the vehicle is driven speedily for a long
controlling devices (emission controls) work to make
distance. In time, the rust, together with the pressure of
the vehicles safe for use in our environment.
through which the poisonous fumes of carbon
The emissions from the gasoline fuel system and
monoxide will seep into the vehicle and can affect the
engine originate from four sources: the fuel tank, car-
occupants, sometimes fatally.
buretor, crankcase, and exhaust. Each source requires
its own controlling device.
Fuel systems on older models of gasoline engines
CAUTION
were vented to the atmosphere. This method of
When you install a muffler, be sure that the
ventilation allowed fuel vapors containing hydrogen
small drain hole in the case is at the bottom, and
and carbon (HC) to escape. When combined, HC and
that the clamp fasteners are tight.
oxides of nitrogen (NOx) cause smog in areas where
there is a large volume of vehicle traffic. This smog
Mufflers must be replaced immediately if they are
causes reduced vision and irritation to the eyes and
known to be defective. Also, they should be replaced if
respiratory system.
suspected of being clogged with carbon particles or
other foreign matter. Inability of the engine to develop
Many
changes
have
been
made
to
maximum power, difficult starting, and operation of the
gasoline-powered equipment in recent years to reduce
engine at higher than normal temperatures may indicate
the emissions and reverse this trend. All of today's
clogging of either the muffler or another part of the
gasoline engines have some type of emission control
exhaust system.
devices installed. They will in one way or another affect
an engine's operation and maintenance procedures. To
The muffler tail pipe or outlet pipe, which extends
perform the necessary maintenance on these engines, it
to the rear of the vehicle (or over the cab on some
is important that you consult the manufacturer's manual
construction equipment and trucks), should be kept
for the specific engine and application. This will allow
open so that the exhaust gases can escape easily. A
you to make repairs and adjustments without reducing
pinched or partly closed tail pipe can affect engine
the effectiveness of these devices.
operation to the extent that the engine may stop. Unless
the used gases are removed from the cylinders, a fresh
Q4-3. What are the primary components of a
mixture cannot enter.
gasoline engine fuel system?
Rain caps should be installed on exhaust pipes that
1. Fuel tank, throttle control button, fuel
extend upward. These caps prevent rain and dirt from
guage, and accelerator pedal
entering the exhaust pipe and engine when the
2. Fuel tank, fuel filter, fuel guage,
equipment is not being used, thus eliminating starting
accelerator pedal, and choke control
and operating problems. The exhaust pipe of equipment
button
with a turbocharger must be sealed when being
3. Fuel tank, fuel pump, fuel filter, carbure-
transported unless the engine is left running. This
tor, and fuel lines
prevents damage to the turbocharger, which could be
4. Fuel tank, carburetor, fuel guage, fuel
caused by air flowing into the vertical exhaust pipe and
lines, and accelerator pedal
turning the turbocharger with no lubrication.
Q4-4. What is the proper fuel-to-air mixture for a
warm gasoline engine?
GASOLINE ENGINE EMISSIONS
1.
15 parts air to 1 part fuel
Air pollution should be a major concern of every
2.
10 parts air to 1 part fuel
American citizen. In many large metropolitan areas
3.
4 parts fuel to 1 part air
where traffic is congested and industry is concentrated,
4.
1 part fuel to 15 parts air
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