Transcript Starting System Service

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
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning
Solenoid Problems (cont'd.)
• Manual
transmissions
have a clutch
start switch
– Should be no
continuity when
clutch pedal is
up
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning