Starting System Service

1
Starting System Service

• Chapter 29

2
Objectives

• Measure amperage draw on a starting system
• Measure voltage drops on both the positive and
  ground sides of the starting circuit
• Diagnose no-crank conditions with a test light
• Replace a solenoid and starter drive

3
Introduction

• This chapter deals with the process for testing
  and repairing starter system problems
• Principles of operation and electrical
  fundamentals in earlier chapters will be
  important
• Today, many starters are replaced with new or
  rebuilt units
• Instead of being repaired in the shop
• Local labor rates dictate whether a starter can
  be rebuilt economically by the shop

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Starting System Service

• Failure diagnosis is important before parts
  replacement
• Most parts stores will not accept returns of
  electrical items
• Testing a starter follow a logical procedure
• Do not skip steps
• Two types of problems
• Mechanical
• Electrical

5
Starting System Service (contd.)

• Visual check
• Check the wiring connections to see they are
  clean and tight
• Cable should not get hot during cranking
• Volt-amp tester
• Used to test the starting and charging systems

6
Starting System Tests

• Low battery voltage biggest cause of starter
  motor failure
• Weak battery solenoid makes a series of rapid
  clicks
• Starter draws twice the current if battery
  voltage drops by half
• During starter tests
• Fuel or ignition system must be disabled
• Do not crank the engine with the coil to
  distributor wire simply disconnected

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Cranking Voltage and Amperage Test

• Using a VAT to check starter motor amp draw
• Clamp inductive pickup around the battery cable
• Cranking test results
• Normally, when the voltage drops, the amperage
  draw goes up
• When there is resistance, there is a voltage drop
• Cranking speed
• Generally, 250 engine rpm is the speed for a
  standard starter

9
Circuit Resistance Test

• Voltage drop testing measures voltage lost when
  current flows from source to load
• No service required if less than 0.6 volt drop
• More voltage drop requires pinpoint tests
• Normal voltage drop about 0.2 volt
• If voltage drop reading is high, check each
  connection in the circuit

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No-Crank Tests Using a Test Light

• Engine does not crank
• Usually because of an open circuit
• Use 12-volt test light to see if there is power
  at the outlet of the solenoid
• If no light, work back through the system until
  you find power
• Next test is to check the starters ground path
• If the light comes on, the ground path is good
• Starter must be the problem

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Solenoid Problems

• Causes of a rapidly clicking solenoid
• Weak battery
• Corroded or loose battery cable connection
• Open circuit in a hold-in winding
• Single click when battery is in good condition
• Often caused by burned contacts in the solenoid
• Park neutral position (PNP) switch
• Moving shift lever while turning ignition to
  start will allow engine to crank
• Start switch should be adjusted

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Solenoid Problems (cont'd.)

• Manual transmissions have a clutch start switch
• Should be no continuity when clutch pedal is up

16
Starter Repair

• Starters may not be economical to rebuild
• Depends on
• Price of parts
• Wages
• Shop work load
• Many shops replace starter drives and solenoids

17
Starter Disassembly

• Considerations
• Mark disassembled parts
• Disconnect solenoids electrical terminals
• Remove two screws that hold solenoid on starter
• Twist solenoid until locking flange is free
• Remove bolts, end frame, and starter body from
  drive end housing
• Remove armature from the housing
• Inspect bearings or bushings at both ends of
  housing

18
Starter Drive Service

• Starter drives often do not last the life of the
  starter motor
• Before replacing the starter drive with a new
  one, count the teeth on the drive pinion
• Match old and new to see they are the same
• Inspect the starter ring gear for damage
• Brushes may wear thin and have to be replaced
• Replace whenever a starter taken apart

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Starter Reassembly

• Some starters have brushes on pivots
• Others require pulling up on springs that hold
  brushes against the commutator

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Pinion Clearance Tests

• Starter on the bench
• Solenoid energized
• Push pinion back toward armature
• Check clearance with feeler gauge
• Starter on the engine
• Check pinion to flywheel ring gear clearance
• Excessive clearance
• Starter can be loud and teeth can be damaged
• Too little clearance
• Starter could bind and amp draw will be higher

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