FAILURE ANALYSIS
81
A properly maintained engine will provide years of
service. Occasionally an engine will fail. An important
part of working on engines is finding out why they
failed. Was it something the customer did? Was it a
manufacturing defect? Did the engine just wear out? All
of these questions need to be answered when a failed
engine is found.
Engines can fail in a variety of ways but most fail-
ures can be classified in the following categories:
• Abrasive ingestion
• Insufficient lubrication
• Over heating
• Over speed
• Mechanical breakage/ wear
NOTE: There may be a combination of failures.
Finding the cause of an engine failure requires the
complete disassembly of an engine and careful exami
-
nation of the parts.
With a good understanding of how the engine
works, close examination of the parts and experience,
an understanding of why the engine failed can be
reached.
Abrasive Ingestion
Abrasive Ingestion is when hard particles are intro-
duced into the engine. Particles can be introduced into
the engine by leaks in the air intake system, through a
dirty oil fill plug or by particles of metal that wore off of a
part, especially during the break in cycle. Particles may
also be introduced through worn or improperly installed
seals or gaskets.
This series of engines is designed to be used on
snow blowers so they are not equipped with an air filter.
When used for snow blowing there is very little risk of
dirt ingestion from the intake air because there is no
dust in the air when it is snowing.
NOTE: Abrasive ingestion from the intake sys-
tem generally is from using the equipment in a
way that it was not designed for such as blowing
hay or cleaning chicken coops. These failures
are not covered under warranty.
1. Abrasive particles that enter the engine through
the intake system can be sand, hay or dirt.
See Figure 11.1.
2. An abrasive particle that enter the engine usually
leave tracking marks were the particles enter the
system. Use these marks to find the source of
the abrasives.
Figure 11.1
CHAPTER 11: FAILURE ANALYSIS
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