Starting System Service - PowerPoint PPT Presentation

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Starting System Service

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Starting System Service Chapter 29 Objectives Measure amperage draw on a starting system Measure voltage drops on both the positive and ground sides of the starting ... – PowerPoint PPT presentation

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Title: 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

4
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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8
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

10
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11
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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14
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

15
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

19
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20
Starter Reassembly
  • Some starters have brushes on pivots
  • Others require pulling up on springs that hold
    brushes against the commutator

21
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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