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The following three conditions must be fulfilled for satisfactory engine start.
1.
The cylinder filled with a proper fuel-air mixture.
2.
Good
compression in the cylinder.
3.
Good spark, properly timed, to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors which
make engine start difficult,
e.
g.,
a
heavy load on the engine when
it
is about to start at low speed, and a
high back pressure due to a long exhaust pipe.
The most common causes of engine troubles are given below
:
10-1
STARTtNG
DlFFtCULTtES
10-1
-1
FUEL
SYSTEM
(1)
No
gasoline in the fuel tank,
or
the fuel cock closed.
(2)
The carburetor is not choked 'sufficiently especially when the engine is
cold.
(3)
Water, dust or gum in the gasoline interfering the fuel flow to the carburetor.
(4)
Inferior grade gasoline
or
poor quality gasoline not vaporized enough to produce the correct fuel-air
mixture.
n
(5)
The carburetor needle valve
is
held open by dirt or gum. This trouble can be detected
as
the fuel flows
out of the carburetor when the engine is idling. (Overflow)
This trouble may be remedied by lightly tapping the float chamber with the grip of a screwdriver or the
like.
(6)
If
the carburetor overflows, excessive fuel runs into the cylinder when starting the engine, making the
fuel-air mixture too rich to burn.
If
this happens, remove the spark plug, and turn the starting pulley a
few turns in order to let the rich fuel-air mixture out of the spark plug hole into the atmosphere.
Keep the choke valve open during this operation.
Dry
the spark plug well, screw it into place, and try to start again.
10-1
-2
COMPRESSION
SYSTEM
If
starting difficulties and
loss
of
power are not due to the
fuel
system or ignition system, the followings
must be checked for possible lack of compression.
(1)
Engine inside is completely dried up because of a long period of storage.
(2)
Loose or broken spark plug. This causes a hissing noise made by mixture gas running out
of
cylinder
in compression stroke during cranking.
(3)
Damaged head gasket
or
loose cylinder head.
A
similar hissing noise is produced during compres-
sion stroke.
A
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56-