AfterMarketNews Auto Care Pro AutoProJobs Auto-Video.com Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service

The Why, Where, When of TPMS Sensors

To understand any TPMS relearn procedure, you have to understand this: Sensors only transmit, they do not receive. No vehicle asks a sensor for information on how it is doing. I know you’re thinking a sensor does receive signals when the vehicle...

Read more...

Most Common Causes of Misfire Codes

A flashing check engine light and a P0301 to P0312 diagnostic trouble code (DTC) is a surefire indication that one or more cylinders are misfiring. Occasional misfires may pass unnoticed, but a steady misfire is hard to miss. The engine usually feels...

Read more...

Pattern Failures of MAF and MAP Sensors

Pattern failures are those failures that happen over and over again — and the same applies to how customers describe these failures. Customers might unknowingly give you the answer to their problem without needing to open the hood. In this article,...

Read more...

Servicing The Electronically Adjustable Shocks Of Full-Sized GM Trucks

Since the 2000 model year, GM has offered electronically adjustable suspension as an option on Chevy, Cadillac and GMC full-size trucks. The system actuates the valving in the shocks to control ­suspension position and body attitude. The electronic...

Read more...

Diagnosing Clutch Assembly Noises

Noise can resonate from many areas of a ­vehicle’s driveline. There are several types of noises associated with the clutch assembly. The release bearing is most often blamed for being the cause of noise when, in many cases, it is not the release...

Read more...

Making Sense Of Steering Angle Sensor Input And Data

Measuring the­ ­position angle, rate of turn and force of the steering wheel is critical for Electronic Stability Control (ESC) systems. Scan tools call these Steering Angle Sensors (SAS) and typically display the information in degrees. The SAS...

Read more...

Internal Engine Oil Consumption Diagnostics

Due to the variables in engine design and ­operating conditions, internal engine oil ­consumption complaints are often the most difficult to solve. In some cases, oil consumption might be more severe under low-speed operation, in other cases, high-speed...

Read more...

Hyundai Fuel System, Emissions Diagnostics

Hyundai has done a good job of improving its ­offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to increase its market share year over year. If you aren’t...

Read more...

Curing Volvo Manual Transmission Rattle

In an effort to increase fuel efficiency, today’s engines produce more torque so they can be ­driven at extremely low rpm. ­Reduced viscosity engine and gearbox oils, less vehicle weight and improved aerodynamics also contribute to better fuel economy....

Read more...

Talk To All Available Modules With Autel's MaxiDiag Elite MD802

Derived from Autel’s Professional Series tool, the MaxiDAS DS708, the MaxiDiag Elite MD802 enables the user to not only get into the OE enhanced OBD II system with mode 6 access and live data graphing, but it also allows a technician to scan the...

Read more...

Reflashing & Reprogramming Tools

In the first half of 2014, NHTSA has issued more than 15 recalls where the fix was to reflash a module on a vehicle. In the same time frame, more than 100 TSBs have also been issued where the solution is to reflash a module. These recalls and TSBs...

Read more...

Pulling Codes: An Advanced Misfire Story The Story of P0301

This article will document code P0301 — Misfire Activity on Cylinder No. 1 — a code many of you have run into, but sometimes we have case studies that are worthy of mention. Our subject vehicle is a 2007 Mercury Mountaineer. The vehicle has...

Read more...
Home ASE Test Prep Diagnostic Dilemmas: Solving Starter And Alternator Problems

Print Print Email Email
On June 15, 1911, Charles F. Kettering was awarded a patent for an electric self-starter for ­automobile engines. Thinking out of the box, Kettering ­designed a small, high-torque motor that would deliver a burst of energy lasting only long enough to initiate the internal combustion cycle. Fortunately for modern commuters, Kettering’s electric self-starter transformed the automobile from a temperamental novelty item into a practical means of transportation. 
 
COMPONENT BASICS
From a historical view, it’s important to remember that Kettering’s conventional field-coil starter required battery power to create the magnetic field needed to make the starter armature turn. During the 1980s, field-coil starters were phased out in favor of “ferrite” permanent-magnet starters.
 
Since the fields in permanent magnet starters don’t require battery power, permanent-magnet starters require much less current to crank an engine. The result is a much lighter, far more efficient starter motor. But, because permanent or ferrite magnets are made of a brittle ceramic material, they are vulnerable to cracking caused by sudden impacts.
 

photo 1: the insulation between the ­commutator segments should be recessed about 1/32” beneath the commutator bars.

Cracked magnets can be tough to diagnose, which is why it’s usually better to replace the starter as an assembly than to repair or rebuild it. See Photo 1.
 
In addition, the rotating mass of the starter ­armature is reduced to create a more compact starter motor assembly. As pictured in Photo 2,

photo 2: in this application, the starter armature is surrounded by six permanent ­magnets.

 
the ­armature on most modern starters terminates into a sun gear mating with a set of planetary gears (see Photo 3) provide the initial gear reduction for the starter.

photo 3: this starter motor terminates into a planetary gear set similar to those used in automatic transmissions.

 
 
A secondary reduction gear can also be used on starters like the one used to illustrate this story. See Photo 4.

photo 4: the secondary reduction drive gear contains an over-run clutch that disengages the starter motor as the engine speed ­increases.

 
The starter “solenoid” is actually a combination of an electric relay and solenoid. The relay portion electrically connects the starter armature to the battery. The solenoid portion mechanically engages the starter’s drive pinion with the ­engine’s flywheel gear. While modern solenoids usually incorporate two high-amperage terminals and one low-amperage, primary activation terminal, some older designs might incorporate an ­additional primary “bypass” terminal that was originally designed to boost ignition coil voltage during cranking. In some applications, the bypass terminal is unused and remains a vestigial remnant of past technology.
 
The starter over-run or one-way clutch is a simple roller-type clutch that’s designed to release when the engine speed exceeds cranking speed. In rare instances, the clutch will seize, which can cause the starter armature to explode from centrifugal force as the engine accelerates. In other cases, the clutch will simply wear out, which usually results in a “whirring” sound, indicating that the starter motor is running, but not engaged to the flywheel.
 
STARTER ACTUATION SYSTEMS
For safety’s sake, the starter’s primary circuit is routed through a neutral safety switch on automatic transmission vehicles and through a clutch safety switch on manual transmission models. With that said, current practice is to reduce the electrical load on the ignition, neutral safety and clutch switches by inserting a starter relay into the starter primary ­circuit. In this case, the above switches activate the starter relay switch rather than the starter’s primary solenoid circuit.
 
Keep in mind also that modern technology in some vehicles has delegated the starter engagement process to the powertrain control module (PCM). In this system, turning the ignition switch or pressing the “start” button simply commands the PCM to engage the starter motor. Failures in these systems should first be diagnosed with a scan tool and by using diagnostic techniques similar to those used in any other system controlled by the PCM. 

BATTERY DIAGNOSTICS
The first step is to make sure that the battery ­terminals and cables are free of corrosion. Next, ­determine the battery state of charge (SOC) and ­condition by testing with a conductance or variable-load, carbon pile battery tester. Recharge or replace the battery as required. Voltage drop from the battery to the starter can be measured by attaching a voltmeter in parallel to the positive battery terminal and to the solenoid B+ terminal.
 

photo 5: corrosion at the lower solenoid terminal on this starter caused an intermittent “clicking,” no-cranking complaint.

The rule of thumb is that voltage drop shouldn’t exceed 0.5 volts during cranking. The voltage drop on the negative ground terminal can similarly be measured by attaching the voltmeter lead to a clean area on the engine block and to the battery B- terminal. Here again, the voltage drop shouldn’t exceed 0.5 volts. See Photo 5.
STARTER CURRENT DIAGNOSIS
Most starter-related electrical failures can be diagnosed by measuring current flow into the starter. ­Actual current flow to the starter can be measured by attaching a 600-amp inductive current probe to the battery positive or negative cables. The probe can be attached to a multimeter with a minimum/ maximum (min/max) recording feature or to a two-channel lab scope.

figure 1: a lab scope display of the relationship between voltage and amperage can provide valuable information about the ­condition of the starter and battery.

 
To illustrate how a starter works on a vehicle in good condition, I’ve included a lab scope recording of battery terminal voltage and starter amperage draw. See Figure 1.
 
The amperage draw begins from the “zero” point at the left. The initial amperage drawn by the solenoid primary circuit occurs at 70 milliseconds (ms).  If the voltage remains at zero, it’s likely that the system has a bad neutral or clutch safety switch, or that the starter relay is defective. If the solenoid amperage remains at 2-3 amps, the solenoid doesn’t have continuity to the starter. Bad solenoid contacts, worn starter brushes or an open-circuit armature can be the cause. In this case, the primary symptom will be a clicking noise as the solenoid primary ­circuit activates. Any of the above failures can result in an intermittent starter engagement complaint.
 
Once the solenoid closes the circuit at 100 ms, the amperage draw increases to 311 amperes at the trigger point. As the ­engine cranks, the amperage draw declines until approximately 300 ms. At about 300 ms, ­amperage rises slightly as the torque load on the starter is momentarily ­increased due to a possible variation in fuel delivery or spark advance.
 
Similarly, battery terminal voltage spikes down to nearly 8.0 volts at 100 ms as cranking amperage is suddenly drawn from the battery. The battery terminal voltage begins to rise to about 10.0 volts at 200 ms as the starter amperage begins to stabilize. As the engine begins to crank, 10.0 volts should be considered the minimum voltage.

Figure 2: At 2.5 milliseconds, available battery voltage drops from about 13.0 volts to 9.19 volts as the starter is engaged.  After the engine starts at 6.3 milliseconds, the alternator begins recharging the battery at 13.8 volts.

 
If the battery won’t maintain 10.0 volts during cranking, the PCM might fail to process data or activate the injector and ignition system drivers. See Figure 2.
BATTERY VOLTAGE GRAPHING
Graphing available battery terminal voltage also provides a direct insight into battery condition. Charging voltage should be achieved approximately two seconds after the engine starts. If charging voltage doesn’t increase within that time interval, it’s likely that the battery doesn’t have enough remaining plate ­capacity to fully support starter current draw. In any case, using a lab scope to display available battery voltage and amperage discharge is an easy way to quickly evaluate battery, starter and starter activation systems.
 
A LOOK AT IDLE/STOP TECHNOLOGY
We’re beginning to see “idle/stop” or “stop/start” technology enter the non-hybrid market, with fuel savings ranging from an estimated 5% to 15% in normal driving. Although a version of idle/stop technology was popularly introduced in a European ­version of Volkswagen in 1983, the technology has a number of issues, including how to power the HVAC and lighting systems while the engine is stopped.
 
Because idle/stop technology obviously requires a rapid discharge/recharge cycle, the absorbed glass mat (AGM) battery most closely meets those requirements. Similarly, idle/stop engine cranking systems include integrated starter/generator systems mounted at the flywheel or connected to the front of the crankshaft by the drive belt.
 
Others use an ­“enhanced” starter motor system that is built to withstand repeated cranking cycles. With the ­advent of direct fuel injection and electronic valvetrains, some manufacturers have explored using fuel and spark timing alone to initiate the internal combustion process. 
The following two tabs change content below.

Gary Goms

Gary Goms is a former educator and shop owner who remains active in the aftermarket service industry. Gary is an ASE-certified Master Automobile Technician (CMAT) and has earned the L1 advanced engine performance certification. He also belongs to the Automotive Service Association (ASA) and the Society of Automotive Engineers (SAE).
Latest articles from our other sites:

Hyundai: Engine Oil Pump Replacement Guidelines During Engine Replacement

Applicable Vehicles: All models Follow the guidelines outlined in this bulletin to install a new oil pump after an internal engine repair or engine short block replacement. Note: A new or remanufactured...More

The Why, Where, When of TPMS Sensors

To understand any TPMS relearn procedure, you have to understand this: Sensors only transmit, they do not receive. No vehicle asks a sensor for information on how it is doing. I know you’re thinking...More

Avoid The 'Warped Rotors' Trap, Find True Pulsation Cause

The expression “warped rotors” still seems prevalent in the brake service community. According to common lore, a warped rotor is the usual cause for pedal pulsation or vibration in the car or steering...More

Getting An Accurate Toyota Tire Pressure

Ambient temperature changes can dramatically alter tire pressure, which could cause a tire pressure monitoring system (TPMS) warning light to illuminate. The TPMS must be initialized based on the tire’s...More

Internal Engine Oil Consumption Diagnostics

Due to the variables in engine design and ­operating conditions, internal engine oil ­consumption complaints are often the most difficult to solve. In some cases, oil consumption might be more severe...More

Hyundai Fuel System, Emissions Diagnostics

Hyundai has done a good job of improving its ­offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to...More

Ernst Offers Socket Boss Universal Twist Lock Socket Tray

Versatility is a must for organizing any socket set. Capitalize on maximum configuration possibilities with the new Universal Twist-Lock Socket Tray from Ernst. Individual rails can be removed or switched...More

Ranger Introduces New Automatic Leverless Tire Changer

Ranger Products, a division of BendPak Inc., is bringing another new tire changer to market. Its latest R80DTXF tire changer features an automatic bead lifter, variable speed turntable and bilateral bead...More