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 ride on commutator bars Brushes transfer electrons from the stationary field coils to the spinning armature

Insulated Brushes Grounded Brushes

Field Coils are Stationary Electromagnets Pole Shoes concentrate the stationary magnetic field

Starting Systems Identify the following components Starter housing or frame Bushings Starter Drive Pinion Over-running clutch

Starter Diagnosis

Allow the armature to drag on the pole shoes Worn out bushings... Allow the 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

P = I x E Cranking Volts Power is required to turn motor 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