© 2012 Delmar, Cengage Learning

Starting System Service

Chapter 29

© 2012 Delmar, Cengage Learning

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

© 2012 Delmar, Cengage Learning

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

© 2012 Delmar, Cengage Learning

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

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Starting System Service (cont’d.)

• 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

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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

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

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

© 2012 Delmar, Cengage Learning

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

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

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 starter’s ground path– If the light comes on, the ground path is good

• Starter must be the problem

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

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

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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

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Starter Disassembly• Considerations

– Mark disassembled parts

– Disconnect solenoid’s 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

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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

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

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

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning