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CHAPTER 9 Two-Stroke Engine Troubleshooting and Evaluation
Copyright Goodheart-Willcox Co., Inc.
during the troubleshooting or evaluation process.
For example, the spark plug name, model, con-
dition, and gap dimension should be recorded.
Make a note if the plug was wet when it was
pulled out. Record every faulty condition you
find on the engine and equipment.
Troubleshooting Procedure
Troubleshooting is the first step in trying to
pinpoint engine or equipment problems in
an attempt to get the unit back into service
as quickly as possible. The goal is not to find
everything that is wrong with the unit, but to
find those conditions that cause the unit to run
poorly or not at all. The repair technician will
make only these repairs and return the unit
back to the customer. Troubleshooting typically
involves the following steps:
• Verify the customer’s complaint.
• Perform a preliminary inspection of the
engine and equipment.
• Perform quick tests on the engine.
Verify the Customer’s Complaint
The customer’s analysis of the problem may
or may not be correct. Whenever possible, it is
good practice to attempt to verify the customer’s
complaint. If, for example, the customer says an
engine is hard to start, try to start the engine.
It is possible that the customer failed to follow
the starting procedure recommended by the
equipment manufacturer. Using an incorrect
starting procedure can lead to a hard starting
or no-start condition. Starting procedures may
vary from one implement to another. For exam-
ple, chain saws from five different manufactur-
ers will have five different starting procedures.
Similarly, a string trimmer will have a different
starting procedure than a blower produced by
the same manufacturer. Therefore, it is import-
ant that the repair technician read and follow
the correct starting procedure for each piece of
two-stroke equipment.
Collect as much information as possible from
the customer to help you troubleshoot the prob-
lem. Ask the customer when the unit last ran,
if anything happened that might have caused
it to stop running, if anyone tried to repair the
unit, how often the unit was used, what type of
gasoline and premix oil was used, how old the
gasoline is, and even what type of container the
gasoline was stored in. Asking these questions
and others will give you information you can
use to help narrow down troubleshooting areas.
Perform a Preliminary Inspection
A preliminary inspection of a piece of two-
stroke equipment can give you a good idea of
the overall condition of the unit. Does the con-
dition of the equipment indicate that it has been
taken care of? Is the equipment dirty, grimy, or
abused? Are any parts missing? The string trim-
mer in Figure 9-2 is missing its guard. Not only
is this unsafe for the operator, but it may cause
engine problems as well. Because the string cut-
ter, which was located on the guard, is also miss-
ing, the string will be allowed to run at a length
greater than normal and may cause the engine to
overheat and eventually seize. Are any fasteners
missing? Is the PTO part of the unit in working
condition? Even though the hedger in Figure 9-3
Debris
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Figure 9-2. This string trimmer is missing the
deflector. The buildup of debris at the deflector
mounting location indicates the deflector has been
missing for a long time.
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Figure 9-3. Moisture on the blades of this hedger
eventually caused rust, which locked the cutters
together.