Comprehensive Guide to Starting System Service & Repair

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 (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

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

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

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 starter’s ground path • If the light comes on, the ground path is good • Starter must be the problem

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 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

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

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