10.
TROUBLESHOOTING
The following three conditionts 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
:
/”-
1
0-
1
STARTING
DIFFICULTIES
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
is
not vaporized enough to produce the correct
(5)
The carburetor needle valve
is
heldopen 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, depending on cases, 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
pulg hole into the atmosphere. Keep the carburetor choke open during this operation.
Dry
the
spark plug well, screw
it
into place, and
try
to start again.
fuel-
air
mixture.
Y
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
(3)
Damaged head gasket or loose cylinder head.
A
similar hissing noise is produced during
(4)
Incorrect valve clearance
of
cylinder in compression stroke during cranking.
compression stroke.
If the correct compression
is
not obtained even after remedying the above, disassemble the
engine and check further
as
follows
:
a)
Valve stuck open due to carbon
or
gum
on
the valve stem.
b)
If
the piston rings are stuck on the piston, remove the piston and connecting rod from
the engine. Clean or replace the parts.
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60
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