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HYDROCARBONS
Hydrocarbons are unbumt gasoline vapors and can be measured in two different ways. The first is to
measure
the weight
of
the pollutants over
a
specific distance such as grams per rn ile or grams per kilometer,
The
second method is to measure
the
concentration
of HC
in the exhaust gas in paPts per million
IPPM).
The most common cause
of
high HC emissions are ignition
system
problems. If the ignition
system
fails t o
ignite the fuel mixture properly, then raw gasoline vapors will pass through the engine i ~ t o the exhaust
system.
Listed
are the
most common ignition problems which mcur and which can
affect
HC emission
output.
IGNITION SYSTEM MALFUNCTIONS
1.
Spark Plugs
-
Fouled, dirty, improper
type
or improperly
gapped.
2. Ignition Timing
-
Advanced
or
Retarded.
3.
f irning Advance
-
Too fast or too
slow
an
advance rate.
4. Battery
-
Low charge
or
faulty.
Carburetion can also lead t o high HC emissions if
the
mixture is either excessively rich or excessively
lean.
MIXTURE-RELATED MALFUNCTIONS
1. Air Cleaner
-
Dirty, over oiled ortorn.
2.
Jets
-
Clogged, restricted or incorrect size.
3.
Float Level
-
Level too low (lean) or too high
(rich).
4. Choke
-
Leakingchoke plunger or sticking linkage.
5, Air Leaks
-
Intake manifolds,
engine gaskets and other
sealing surfaces.
6.
Synchronization
-
Unbalanced on rnulticylinder machines,
7. Exhaust System
-
Restricted flow or improper exhaust system.
Engine wear or damage can also cause high MC emissions.
I .
Rings
-
Low compression, leakage into crankcase.
2.
Valves
-
Improper
adjustment, bent stem or burnt.
3. Gaskets
-
Leaking, loss of compression.
4. Crank Seals
-
Leaking.
5. Oil Consumption
-
Worn valve guides, worn rings, clogged crankcase breather.
6.
Oil
-
Improper engine oil.
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