WM 90 Repair Troubleshooting
wc_tx000393gb.fm 99
12. Troubleshooting
12.1 Troubleshooting Introduction
If the engine shows any sign of malfunction, the cause should be
determined immediately and the appropriate countermeasures should
be taken to prevent the problem from worsening. This troubleshooting
section describes certain known problems, their possible causes, and
appropriate action to take. Note, however, that the list of problems
listed here is not all-encompassing. Generally speaking, since there is
the possibility of multiple causes for a single problem, please use your
experience and common sense when deciding on what action to take.
The following three conditions must be met for the engine to start:
1. The cylinder must be filled with the proper fuel-air mixture.
2. There must be good compression in the cylinder.
3. There must be good spark, properly timed to ignite the mixture.
The engine cannot be started unless the these three conditions are
met. There are other factors as well that will make engine starting
difficult, such as a heavy load on the engine when attempting to start,
or heavy back pressure due to a long exhaust pipe.
12.2 Troubleshooting Procedures
12.2.1 Fuel System Problems:
12.2.1.1 No gasoline in tank, or the fuel cock is closed.
12.2.1.2 The carburetor is not choked sufficiently especially when engine is
cold.
12.2.1.3 Water, dust or gum in the gasoline interfering with fuel flow to
carburetor.
12.2.1.4 Inferior grade gasoline or poor quality gasoline not vaporized enough
to produce the correct fuel-air mixture.
12.2.1.5 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.
12.2.1.6 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
to let the rich fuel-air mixture out of the spark plug hole and into the
atmosphere. Keep the choke valve open during this operation. Dry the
spark plug well, screw it into place, and try to start the engine again.
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