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

BMW Recognized for Engine-Building Excellence

BMW Group’s engine-building prowess was recognized with four wins at the latest International Engine of the Year Awards. The drive unit in the BMW i8 earned two class wins as well as being declared overall winner, with a further class win being garnered...

Read more...

Diagnostic Dilemma: The Case of the Missing Code

When doing mobile diagnostic work, no-code stalling complaints are a major part of your agenda. In most cases, the client shop is simply too busy to duplicate the failure or, in some cases, a long test drive will yield nothing in the way of useful...

Read more...

Secondary Ignition: The Art of Spark

What is a coil? From the beginning of the internal combustion engine, several different ignition systems have been used to create a high-energy spark. The most popular system, and the one that’s in use today, is a step-up coil. A coil is nothing...

Read more...

Regulators Launch Investigation Into Jeep Grand Cherokee Brake Defect

Federal regulators are investigating whether the automatic braking systems in some 2014 Jeep Grand Cherokees may be defective after receiving a number of complaints from motorists about a potentially dangerous glitch that caused their vehicles to come...

Read more...

Electronic Proportioning Valve: Doing More With Less Hardware

Anti-lock brake systems (ABS) and the HCU are replacing proportioning, combination and other valves to change the braking forces in the front and rear. This is called Electronic Brake Distribution (EBD) and it can dynamically change the proportioning...

Read more...

NHTSA’s GM Brake Line Corrosion Investigation: Reading Between the Brake Lines

There will be no recalls on some GM vehicles for brake line corrosion. Instead, we received an advisory from the National Highway and Traffic Safety Administration (NHTSA) about brake line inspection and car washes. What was not discussed was the corrosion...

Read more...

Customer Loyalty to Vehicle Brands Spells Ongoing Maintenance Opportunities

Vehicle owners’ allegiance to brands should give us all something to cheer about. This is especially true for those of you who service import vehicles. Nine import nameplates — Infiniti, Land Rover, Lexus, Mazda, Mitsubishi, Nissan, Porsche, Subaru...

Read more...

The Element of Trust And Its Impact on a Repair Scenario

Trust: It’s an important word, and it’s one I hear a lot behind the counter at the shop. “I know you’ll treat me right because I trust what you do,” is the general sentiment. But I’ve always wondered how deep that level of comfort goes...

Read more...

Servicing Mercedes-Benz AIRMATIC Suspensions

The Mercedes-Benz AIRMATIC suspension system was introduced in 1999 on the S-Class and has subsequently been used on the E-Class and most of the automaker’s SUVs. The system employs electronically controlled air springs that provide an ideal balance...

Read more...

Ingersoll Rand's 'Real Work Real Play' Sweepstakes With Gas Monkey Garage And NASCAR Rewards A Tool User With The Ultimate Fan Weekend

Ingersoll Rand, the Official Power Tools of NASCAR and a preferred tool provider for Gas Monkey Garage, has announced the “Real Work Real Play” sweepstakes to reward automotive fans who “get it done” with a weekend of fun. Ingersoll Rand is working...

Read more...

Bosch Relaunches Boschdiagnostics.com With Mobile-Responsive Design, New Layout For North America

Bosch has announced the re-launch of boschdiagnostics.com in North America, continuing to update all of its sites to a mobile-responsive, intuitive design. The URL contains three separate sites, featuring DIY diagnostic tools (DIY), professional diagnostic...

Read more...

New Bartec Tech400Pro TPMS Tool To Be Demonstrated At NACE | CARS

Bartec USA, a North American leader in TPMS Diagnostic tools, will hold live demonstrations of its newly released Tech400Pro TPMS Scan Tool at this year’s NACE | CARS show in Detroit. Michael Rose, Bartec product manager, will conduct these demonstrations...

Read more...
Home ASE Test Prep Diagnostic Solutions: Starter & Battery Diagnostics

Print Print Email Email

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

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

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

In addition, the rotating mass of the starter ­armature is reduced to create a more compact starter motor assembly. photo 4: the secondary reduction drive gear contains an over-run clutch that disengages the starter motor as the engine speed increases.As pictured above (see Photo 2), 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. A secondary reduction gear can also be used on starters like the one used to illustrate this story. See Photo 4.

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 “by-pass” terminal that was originally designed to boost ignition coil voltage during cranking. In some applications, the by-pass 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 DIAGNOSISfigure 1: a lab scope display of the relationship between voltage and amperage can provide valuable information about the condition of the starter and battery.

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. 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.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.

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. 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 import 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:

Top 10 Fuel Pump Fails

10. Strainer Blocks Fuel-Level Sender A fuel pump inlet strainer may be installed that is interfering with the travel of the fuel-level sensor’s float arm, which causes an optimistic fuel level...More

GMC Yukon No-Cranking Complaint: The 1,300-Mile Test Drive

This month’s Diagnostic Dilemma is about the technical and professional issues involved with attempting to diagnose an extremely random no-cranking complaint on a 2003 GMC Yukon equipped with the 5.3L...More

Chrysler Tech Tip: Stability Control System Engages Prematurely

Problem:  ESP system may prematurely activate momentarily when negotiating a curve or MIL illumination due to diagnostic trouble code P0340, P0344 or P0116. Overview: This bulletin involves selectively...More

Honda Tech Tip: Dampers Lock Up After Lowering Vehicle on a Rack

You’ve got your service customer’s vehicle up on a rack to do some work. You lower it back down, but now it looks like a 4x4 ready for some serious off-roading or it feels like it’s got a rock-solid...More

Customer Loyalty to Vehicle Brands Spells Ongoing Maintenance Opportunities

Vehicle owners’ allegiance to brands should give us all something to cheer about. This is especially true for those of you who service import vehicles. Nine import nameplates — Infiniti, Land Rover,...More

Top 10 Subaru Articles

We're counting down the top ten most effective Subaru technical articles ever! 10) Tech Tip: Subaru Impreza With DTCs P0705, P0851, P2746, P2750 And/Or No Crank, No Start If you receive a customer...More

Autel's MaxiSYS Elite Offers Faster Processor, New Docking Station

The MaxiSYS Elite is the latest addition to Autel’s MaxiSYS family of diagnostic tools. The new Elite features a faster processor, higher screen resolution, faster WiFi, longer battery life and Android’s...More

Save Time Installing TPMS Using Dill's Preset Torque Tools

Dill TPMS Torque Tools are designed to easily install the hex nut on the valve stem. The torque values are preset, eliminating the need to adjust a torque wrench before and after install. Dill’s...More