9.
TROUBLE
SHOOTING
The following three conditions must be satisfied for satisfactory engine start.
1.
The cylinder filled with a proper fuel-air mixture.
2.
An appropriate compression in the cylinder.
3.
Good sparks at the correct time to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors which make engine start dif-
ficult, 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,
just
to say a few.
The most common causes of engine troubles are given below:
9-1
STARTING DIFFICULTIES
9-1
-1
FUEL SYSTEM
NO
gasoline in th fuel tank; or the fuel cock is closed.
The carburetor is not choked enough, particularly when the engine is cold.
Water, dust
or
gum in the gasoline block flow of the fuel to the carburetor.
Inferior grade gasoline
or
poor quality gasoline is not gasfied enough to produce the correct fuel-air mixture.
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, depending on cases, by lightly tapping the float chamber with the grip of a screwdriver
of the like.
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 carburetor choke open during this
operation. Dry the spark plug well, screw it into place, and try
to
start again.
9-1-2
COMPRESSION
SYSTEM
If
starting difficulties and
loss
of power are not due to the fuel system
or
ignition system, the following must be checked for
possible lack of compression.
1)
Engine inside
is
completely dried up because of a long period of non-operation.
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 compression stroke.
4)
Incorrect Tappet Clearance
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, and clean, remedy
or
replace the parts.
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30
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