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Starting Systems
State a major safety precaution when
removing or working around a
starting motor
Don’t make your starter
an Arc Welder!
Always unhook the battery ground
Before removing the starter motor
Starting Systems
Identify the following components
Armature
Commutator
Brushes
Pole Shoe
Field Coil
Starter Armatures
The Armature is a rotating
electromagnet
Commutator bars allow current in
and out of the armature
Brushes
Brushes ride
transfer
on commutator
electrons from
bars
the stationary field coils to the
spinning armature
InsulatedBrushes
Brushes
Grounded
Field
Coils
are
Stationary
Pole Shoes concentrate the
Electromagnets
stationary magnetic field
Starting Systems
Identify the following components
Starter housing or frame
Bushings
Starter Drive Pinion
Over-running clutch
Starter Diagnosis
Worn
outthe
bushings...
Allow
armature to
drag on the pole shoes
This will slow the starter
and INCREASE amp draw
Worn or Dry
Armature shaft will
INCREASE amp flow
Burned commutator bars
restrict the amp flow
Worn out brushes
DECREASE amp flow
There will be more questions...
...On the test….
…than I am covering here.
Read your book…
and complete Starter Labs
Test the Starting System
Check Cranking RPM
Check Cranking Volts
Check Cranking Amps
Low Cranking RPM
A slow turning starter will pull extra amps
Could be caused by tight engine
(New Engines)
Can be caused by advanced timing
Low Cranking RPM
Low cranking RPM….
…With low cranking Amps…
Bad Starter
Worn brushes, Bad commutator bars,
open in field or armature
Cranking Volts
Power is required to turn motor
P=IxE
Low volts will cause high amps
Low Cranking Volts
Cranking volts at battery should be over 10V
Load test battery if low cranking volts
Excessive amp draw can cause low cranking volts
in a good battery
High Cranking Amps
Check voltage drop across
STARTER MOTOR
If Battery cranking volt is 1/2 volt more
than Starter volt drop diagnose battery
cables and connections
If cranking volts are within
1 volt of battery…
Insure engine turns freely
Insure ignition does not cause slow turning engine
Replace Starter Motor
(assuming there are excessive amps)
Before you install the rebuilt starter
Bench test the replacement
It may save you a starter R & R
Starting Systems
Understand the operation of the two starting
circuits
#1 Starter Control Circuit
#2 Starter Motor Circuit
Starter Solenoid
Understand the function of the Pull In
solenoid windings….
…and the hold in solenoid windings
Starter Solenoids
Predict the effect of an open circuit in the
solenoid pull in windings….
….and the solenoid hold in windings
Notice pitted contact ring
24 Volt Series/Parallel Switch
Understand how 12 volt batteries can be
used to run a 24 Volt starting system
Series/Parallel Switch
Diagnose a defective series parallel switch
using a volt meter
Starter Control
Identify variations in starter control circuits
Test the Starting System
The Bottom Line
Test cranking RPM
Test Cranking Volts
Test Cranking Amps