4.SELF-STARTER ASSEMBLY, PERFORMANCE TESTING AND REMOUNTING
In this lesson, we will study the assembly and remounting of the starter motor and also about its testing to ensure that it performs flawlessly after being fitted in the car. We will study three tests – the pull-in test, the hold-in test, and the no-load performance test.
4.0 i. ii. iii.
4.1 • • • • •
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Objectives After going through this lesson, you will be able to: Assemble the self starter. Conduct three performance tests – the pull-in test, the hold-in test and the noload performance test. Remount the self starter in the car.
Assembly of Starter Motor Apply oil to the armature shaft splines and insert the shaft in the splined sleeve. Check the pinion and sleeve assembly for free movement. Insert the armature stop ring and the armature ring from the end of the shaft and fix the armature ring in its groove on the shaft. Mount the stop ring onto the ring. Apply oil to the bush in the drive end housing and on the shaft end and insert the armature shaft in the housing so that the shift lever is properly installed in the switch cover. Move the shift lever back and forth and check for free movement of the pinion assembly. Install the field assembly over the armature.
For installing the field assembly over the armature, the plastic piece is placed in position and then the yoke is mounted over the armature so that the notch in the yoke is located in the projection of the piece. This is provided so that the field poles are properly placed around the armature and the yoke does not turn from its position. • • •
Place the washer over the commutator. Fix the brush in its holder and back it up with spring pressure. Push the brushes back against spring pressure and insert the brush holder plate over the armature shaft so that the brushes ride over the commutator.
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Place the insulation strip in the commutator end housing properly and fix the housing in place. Insert the two long bolts from the side and screw them in the drive-end housing. Tighten the bolts with a spanner. Place the armature brake spring and slide in the armature plate. Place the commutator end cap and tighten the two nuts with a screw driver.
Next, the magnetic switch is fixed to the motor. The following sequence of steps is followed to accomplish this: • • • • •
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Apply oil over the plunger, slide the spring over it and then check for its free movement in the switch housing. Remove the plunger and install it in the switch cover so that its collar is held behind the shift lever. Slide the spring over the plunger and then mount the switch housing. Screw in the two bolts and tighten them with a No. 10 ring spanner to hold the switch firmly. Place the wire connector of the field coil, coming from the motor, over the ‘M’ terminal of the switch and tighten the nut.
Performance Testing
In the preceding sections, we looked at the procedure for dismantling, inspection and assembling the starter motor assembly. Let us now study some tests that need to be performed to establish that the motor will function properly. These tests may also be performed when any trouble is reported, in order to determine the actual fault. It is important to take care that the tests do not last more than three to five seconds, or this could result in the burning of the coil. 4.2.1 Pull-in Test •
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Disconnect the field coil lead from terminal ‘M’ of the switch before proceeding with the test. This is done because only the switch needs to be tested and there should not be a supply current to the motor. Connect the battery negative to the ‘M’ terminal of the switch and to the motor body. Touch the battery positive to the ‘S’ terminal of the switch. This should pull the plunger in and throw the pinion out. Failure to do so calls for replacement of the magnetic switch.
4.2.2 Hold-in Test •
Disconnect the negative lead from terminal ‘M’ of the switch. This opens the circuit of the pull-in coil and the hold-in coil alone keeps the plunger in position. If the plunger returns back, that is, if the pinion is pulled inwards, it means that the
hold-in coil is not able to keep the plunger inwards and the magnetic switch must be replaced. The same set-up is also used to check whether the plunger returns immediately after the hold-in coil circuit is opened, that is, the ignition key in the main switch is released. For this: •
Disconnect the negative lead from the motor body. The plunger should return to its original position. If the plunger and pinion do not return to their respective original positions, the switch should be replaced.
4.2.3 No Load Performance Test • • • •
4.3 • •
Connect the positive lead from battery to the ‘B’ terminal of the magnetic switch. Connect the battery negative to the motor body. Touch the lead from the battery positive to ‘S’ terminal of the switch. The pinion should move out as well as spin freely. Connect an ammeter between the battery and ‘B’ terminal on the switch to determine the current being drawn by the motor. This current should be less than 50 amperes.
Remounting Unscrew the two mount bolts from the clutch housing and place the motor in the hole in the clutch housing so that the pinion is towards the flywheel ring gear. Screw in the two bolts and tighten them with a socket and ratchet handle.
After the motor has been tightened firmly in position, the electrical connections are made. • • • • • • • •
Connect the lead wire from the ignition coil to the light duty ‘M’ terminal and the other lead wire coming from the switch to the ‘S’ terminal. Connect the battery positive cable at the heavy duty ‘B’ terminal at the switch. Place the battery box on the bracket and keep the battery in it. Clean the sulphate deposits from the clamp and tighten the clamp to the positive terminal of the battery. Tighten the ground cable clamp to the negative battery terminal in a similar manner. Fix the battery clamp firmly but not too tightly. Apply petroleum jelly to the terminals and shut the bonnet of the car. Get into the car and turn the key in the main switch and ensure that the starter motor cranks the engine effortlessly.
Self-check Questions
1. 2. 3. 4.
Name the 3 performance tests done on the starter motor. What is done before doing the pull-in test and why? How is the pull-in coil circuit opened for doing the hold-in test? What is the no-load current? Table 4.1 Self-starter trouble shooting Defect Armature fails to rotate or rotates slowly and the starter does not crank the engine though pinion has engaged with the ring gear.
Armature rotates but pinion fails to engage
Starter continues to run after the switch is released
Cause
Action
Discharged/Defective battery
Substitute a fully charged battery. If the starter now cranks the engine, then the battery must be attended to.
• Loose or oxidized battery terminals. • Corroded or loose connectors • Defective earth connection.
Clean the terminals and smear petroleum jelly. Tighten all connections.
• Brushes worn out and not making proper contact with commutator • Dirty or oily or badly burnt commutator • Starter terminal or brush box having an earth fault • Defective solenoid switch • Defective armature field coils
Remove the starter for further inspection.
Pinion sticky on shaft
Shaft splines and the pinion internal splines to be cleaned and lubricated
Burrs on pinion or ring gear
De-burr by filling
Worn out CE/DE bush
Replace the defective bushes
Sticky starting switch
Disconnect starter cable immediately at starter or battery terminals. Replace starter switch.
Sticky solenoid switch contacts
Remove the starter solenoid for inspection.
Bush in pinion seized on shaft /ring gear fouled or damaged
Remove the starter from the vehicle. Clean thoroughly, deburring pinion and ring gear by filing.
Armature rotates, pinion engages with the ring gear but the engine is not cranked. (A whining noise is heard)
4.4
Clutch slip
Remove the starter from the vehicle for repair.
Assignments
4.4.1 Class Assignment 1. Discuss the tests conducted during performance testing. 4.4.2 Home Assignment 1. Revise the trouble-shooting chart.
4.5
Summing Up
In this lesson, we assembled the starter motor and studied about its testing to ensure that it performs flawlessly after being fitted in the car. We studied about three tests – the pull-in test, the hold-in test, and the no-load performance test. We also studied that the solenoid switch has two coils – the pull-in coil and the hold-in coil, which generate a magnetic pull together to pull in the plunger and to close the switch contacts. Once the contacts are closed, the hold-in coil alone should be able to hold the plunger in place. This is done to remove the resistance of the pull-in coil from the circuit and, thereby, obtain a larger current for starting.
4.6
Possible Answers to Self-check Questions
1. pull-in test, hold-in test, no-load performance test 2. the field coil lead is disconnected from terminal ‘M’ of the switch because current is not to be supplied to the motor (we need to test the switch, not start the motor) 3. by disconnecting the negative lead from terminal ‘M’ of the switch 4. 50 amp
4.7
Terminal Questions
1. Describe how you would do the 3 performance tests. 2. Describe the installation procedure of the starter motor.
4.8
References
1. Maruti 800 Service Manual
4.9
Glossary
Pull-in Test
Performance Test of the magnetic switch to test the pulling of plunger in and throwing the pinion out.
Hold-in Test
The performance test of the magnetic switch to keep the plunger in position.
No load performance test
Standard performance test of the starter motor at no load to examine whether the specified current is flowing between battery and the terminal on the switch.
Sulphate deposit
White deposits generally developed on the positive terminal.