chap40 pps Automotive technology at University of Cambridge

start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 40, the reader should be able to: • • • • Describe how the cranking circuit works Explain how to disassemble and reassemble a starter motor and solenoid Discuss how to test the cranking circuit Describe how to perform cranking system testing procedures Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: ampere-turns • armature bench testing • brush-end housing • brushes commutator-end housing • commutator segments • compound motor (compound-wound) • compression spring • counter- electromotive force (CEMF) • cranking circuit drive coil • drive-end (DE) housing • electromagnetic switch field coils • field poles Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: gear-reduction starters • ground brushes • growler tester holding coil • hold-in winding • hot brushes lap winding main field housing • mesh spring • mica • movable pole shoe neutral safety switch • overrunning clutch permanent-magnet field • plunger lever • pole shoes • positive-engagement starter • pull-in winding Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: remote vehicle start (RVS) series motor • shift fork lever • shunt motor • solenoidoperated starter • starter drive through bolts undercut voltage-drop testing wave winding Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 For any engine to start, it must first be rotated It is the purpose and function of the cranking circuit to create the necessary power by converting electrical energy from the battery into mechanical energy at the starter motor and rotate the engine Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 CRANKING CIRCUIT The cranking circuit includes mechanical and electrical parts  required to crank the engine for starting. Early 1900s cranking  force was the driver’s arm. Modern cranking circuits include: The Starter motor. The starter is normally a 0.5­ to 2.6­ horsepower (0.4 to 2.0 kilowatts) electric motor that develops  nearly 8 horsepower (6 kilowatts) for a very short time when first cranking a cold engine Figure 40–1 A typical solenoid-operated starter Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The Battery. The battery must be of the correct capacity  and be at least 75% charged to provide the necessary current  and voltage for correct operation of the starter The Starter solenoid or relay. The high current required by  the starter must be able to be turned on and off. A large  switch would be required if the current were controlled by  the driver directly. Instead, a small current switch (ignition  switch) operates a solenoid or relay that controls the high  starter current The Starter drive. The starter drive uses a small gear that  contacts the engine flywheel gear and transmits starter motor  power to rotate the engine Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The Ignition switch  The ignition switch and safety control  switches control the starter motor operation.  Figure 40–3 A typical wiring diagram of a starter circuit Figure 40–2 Some columnmounted ignition switches act directly on the contact points, whereas others use a link from lock cylinder to ignition switch The engine is cranked by an  electric motor controlled by a key­operated ignition switch.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The ignition switch will not operate the starter unless the  transmission is in neutral or park. Many manufacturers a neutral  safety switch that opens the circuit between ignition switch and  starter to prevent operation unless the gear selector is in neutral or  park Neutral safety switches can be adjusted by loosening the hold­down  screws and moving the switch slightly to be certain the engine will  crank only with the transmission in the neutral and park positions Many manufacturers use a mechanical blocking device in the  steering column to prevent the driver from turning the key switch to   start unless the gear selector is in neutral or park. Many manual  transmission vehicles also use a safety switch to permit cranking  only if the clutch is depressed Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Starter Drive­to­Flywheel Clearance  For proper operation of the  starter and absence of abnormal starter noise, there must be a slight  clearance between the starter pinion and the engine flywheel ring gear.  If clearance is too great, the starter  will produce a high­pitched whine  during cranking.  Figure 40–41 A shim (or half shim) may be needed to provide the proper clearance between the flywheel teeth of the engine and the pinion teeth of the starter If the clearance is too small,  the starter will produce a high­ pitched whine after the engine  starts, just as the ignition key is  released Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOTE: Be sure that the locking nuts for the studs are tight. Often the  retaining nut that holds the wire to the stud will be properly tightened, but  if the stud itself is loose, cranking problems can occur Many GM starters use shims (thin metal strips) between the  flywheel and the engine block mounting pad to provide the proper  clearance.  NOTE: Some manufacturers use shims under starter drive­end housings  during production. Other manufacturers grind the mounting pads at the  factory for proper starter pinion gear clearance. If any GM starter is  replaced, the starter pinion must be checked and corrected as necessary to prevent starter damage and excessive noise Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 To be sure the starter is shimmed correctly, use this procedure: Step #1  Place the starter in position; finger tighten mounting bolts Step #2  Use an 1/8 inch diameter drill bit (or gauge tool) and insert  between the armature shaft and a tooth of the engine flywheel Step #3  If the gauge tool cannot be inserted, use a full­length shim  across both the holes, moving the starter away from the flywheel Step #4  If the gauge tool is loose between the shaft and the tooth of  the engine flywheel, remove a shim or shims Step #5  If no shims have been used and the fit of the gauge tool is  too loose, add a half shim to the outside pad only. This moves the  starter closer to the teeth of the engine flywheel Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 CAUTION: Be sure to install all factory heat shields to help ensure  proper starter operation under all weather and driving conditions NOTE: The major cause of broken drive­end housings on starters is too small a clearance. If the clearance cannot be measured, it is better to put a shim between the engine block and the starter than to leave one out and risk breaking a drive­end housing Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Ground Wire Current Flow - Part Before installing a new or rebuilt starter in a vehicle, be sure that both the positive cable and the negative cable are in good condition The reason is all electrical power must have a complete path from the power source, through the electrical loads, and back to the power source This rule is true for all circuits, whether series, parallel, or series-parallel type As the current flows through resistances and loads (such as bulbs and coils), its voltage decreases because of the resistance (electrical load) in the circuit Amperes is the unit of electricity that actually does the work in a circuit The greater the current flow, the more electrical power available Because current flow is actually a measure of the number of electrons making the trip through a circuit, this same number of electrons also must return to the power source The electrical pressure (voltage) on the return (ground) wires is low (almost zero), but the current in amperes must still flow back to the battery The battery ground cable must be just as large as the positive cable because just as many amperes return as leave the battery Still not convinced? Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Ground Wire Current Flow - Part Connect a starting-charging-testing unit to a vehicle Instead of connecting the ampere probe around the positive cable, connect it around the ground cable (all cables should be within the ampere probe if more than one ground cable is connected to the battery terminal) All ammeter readings should be the same if taken on the positive or negative cables of the battery NOTE: Most starting­charging­testing units use an arrow on the ammeter  probe to show polarity. Reversing the direction in which the arrow points  is often necessary to read the correct polarity (positive or negative) on the  tester display Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Reuse Drive-End Housings to Be Sure Most General Motors starter motors use a pad mount and attach to the engine with bolts through the drive-end (nose) housing Many times when a starter is replaced on a GM vehicle, the starter makes noise because of improper starter pinion-to-engine flywheel ring gear clearance Instead of spending a lot of time shimming the new starter, simply remove the driveend housing from the original starter and install it on the replacement starter Because the original starter did not produce excessive gear engagement noise, the replacement starter should also be okay Reuse any shims that were used with the original starter This method is better than having to remove and reinstall the replacement starter several times until the proper clearance is determined Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 STARTING SYSTEM TROUBLESHOOTING GUIDE See the chart  on Page 432 of  your textbook.  Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Starter Overhaul Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Starter Overhaul (cont.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Starter Overhaul (cont.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Starter Overhaul Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman (cont.) ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY All starter motors use the principle of magnetic interaction  between the field coils attached to the housing and the  magnetic field of the armature Proper operation of the starter motor depends on the battery  being at least 75% charged and the battery cables being of the  correct size (gauge) and having no more than 0.2­volt drop Voltage­drop testing includes cranking the engine, measuring  the drop in voltage from the battery to the starter, and  measuring the drop in voltage from the negative terminal of  the battery to the engine block Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) The cranking circuit should be tested for proper amperage  draw An open in the control circuit can prevent starter motor  operation Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458