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TM 10-3930-671-24
6.11. Starting System Troubleshooting
Troubleshooting Procedures ................................................................................................. F-297
Starting System Mechanical Checks..................................................................................... F-298
Starting System Electrical Checks ........................................................................................ F-299
Volt Drop Tests...................................................................................................................... F-303
Troubleshooting Procedures
When diagnosing and correcting the cause of trouble with an engine starting system, do not begin by disconnecting wires
or disassembling components. Instead, start by analyzing the complaint or symptoms. Then, systematically determine the
probable cause. Make a preliminary investigation of the trouble, as follows:
1.
Check with the operator or his supervisor before
you start troubleshooting. Ask the operator the
following:
a)
When did the trouble occur?
b)
Is the trouble accompanied by any other
faulty conditions?
c)
How did the trouble happen? Did the
trouble happen suddenly? Any abnormality
before the trouble happened?
d)
Had the engine or truck electrical system
recently been repaired when the trouble
occurred? When?
e)
Has the same trouble occurred before?
f )
Does trouble occur when hot, cold or
both?
2.
Be sure the problem exists. If it is difficult to
judge whether a faulty condition requires repair,
perform all of the diagnostic electrical checks
and tests.
3.
It is possible to avoid unnecessary disassembly
work by diagnosing the cause of the trouble
accurately on the basis of the questions asked of
the user. Take the time necessary for sufficient
preliminary investigation. Hasty disassembly
work can also make it difficult to reproduce the
troubled condition and, sometimes, lead to
disappearance of the evidence of the cause of
the trouble.
4.
Start with the easiest and least time consuming
solution. When several items are suspected to
be the cause of the trouble, examine them,
starting with the easiest one.
5.
Try to think of the reason why the trouble
happened. Do not confine your effort to the
correction of the present trouble, but try to detect
the fundamental cause, if any, of the trouble and
correcting or adjusting it.
6.
A good rule to follow in locating trouble is to
never remove or make an adjustment to more
than one component at a time. Locate the
trouble by a process of elimination. The cause is
usually simple, rather than mysterious and
complicated.
7.
When troubleshooting an engine cranking or
starting system, keep in mind that more than the
starter is involved. The cranking motor is only
one of the elements in the starting system. The
motor, battery, wiring, and switches all make up
the system and each contributes to the proper
functioning of that system.
8.
It will be helpful to have a good understanding of
solenoid, motor, and circuit operation.
9.
The following is an important point. The starter
demands high current flow from the battery to
perform its job. It is essential that the switches,
wiring, and connections do not have high
resistance which can cause arcing or heat
damage to components and excessive battery
current use during starter operation. All
electrical connections must be clean and tight for
minimum
resistance.
This
is
especially
important for the battery cable connections at the
battery terminals.
10.
The starter is a special type electric motor that
operates on low dc voltage and must be able to
withstand extremely high current. The high
current carrying requirement means that the
motor can be operated for only short periods of
time. To prevent overheating, periods of
operation of more than 30 seconds in duration
are not recommended.
F-297
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