Starter Motor: The Definitive Guide



Starter Motor: The Definitive Guide


starter-motor-guideEvery vehicle, whether a modern or older model will have a starting system. At the heart of it all is the starter motor. Also known as self-starter, electric starter motor or cranking motor, the automotive starter motor is such as an essential device. The starter is so important in a car that its absence or malfunction can mean an automobile that will not move. Knowing about this device can help you ensure your motor vehicle always starts when you want it to.

We prepared this starter motor guide to make you an informed car owner or auto parts dealer. It contains information about the different types of starter units- from self starter motorcycle variant to the self starter car version. We delve into the parts that make the device, from the starter motor solenoid to the brushes in the motor unit.

To helps you diagnose and troubleshoot a failed solenoid starter motor, we have highlighted the signs to look out for and how to deal with each. We also provide advice on how to buy a starter motor, whether a for a passenger car, truck or motorbike. In short, the guide contains everything you might have wanted to know about electric starter motors. Let us get started.

Chapter 1: Starter Motor Definition

Chapter 2: Starter Motor Parts

Chapter 3: Starter Types

Chapter 4: Starter Motor Categories By Starting Methods

Chapter 5: Starter Motor Problems

Chapter 6: Starter Motor Troubleshooting Methods

Chapter 7 Starter Motor Buying

Chapter 1

Starter Motor Definition


Starter Motor Guide

A starter motor is the component that is used to start an internal combustion engine. There are several types of starters, each with own method to produce rotation. This guide is about the electrical starter motor, which is the most common across different vehicles today.

Usually mounted near the transmission, this type of starter consists of a small electric motor, a pinion drive, and a starter solenoid. The three parts are joined, with the solenoid sitting on top of the motor and the pinion drive the motor shaft.

Starter motors form part of a vehicle’s starting system that comprises the battery, ignition switch, starter relay, cables, and the ring gear on the engine flywheel. The starter system in an automatic transmission will also have a neutral safety switch, which is the equivalent of the clutch switch used in manual transmission vehicles.

Starter systems were not always electric. The first versions were operated by hand. These manual motor starters were not only inefficient but also dangerous. There were often accidents from flying crank handles, some even fatal. That prompted the invention of starters that did not require manual cranking.

The automotive starter system has evolved a lot to become what it is today. The modern version is much more effective, with components that are highly efficient and durable. It is not unlikely to find a starter solenoid, starter motor, or battery that lasts hundreds of start sessions without failing.


Starter Motor Function

The purpose of motor starter system is to crank up a vehicle’s engine so it can start running. It does that with the help of the battery, starter motor and starter solenoid. What is the purpose of starter solenoid in all this? You may ask. As we will see later, the starter starter solenoid serves a very useful purpose.

One, it helps close the circuit that moves current through the starter motor to cause it the start working. Two, the solenoid works a plunger that pushes the pinion drive to mesh the pinion gear with that on the flywheel. That transfers the energy of the spinning motor to the flywheel and causes the engine to start.


Starter Motor Function

Starter Motor Working Principle

Starter Motor Working Principle

The working principle of starter motor is fairly simple and easy to understand. Here is what happens in a typical electrical starter motor system.

When you turn the ignition key to the START position or press the START button in the newer vehicles, a small current flows to activate the starter relay. The starter relay, in turn, works a circuit that provides a larger current to the starter solenoid. As we saw earlier, the solenoid closes contacts to complete a circuit that sends a large amount of current from the battery to the starter motor. The motor then begins to rotate.

Meanwhile, the starter solenoid will also have also pushed a rod forward. The movement works a mechanism to push the pinion gear to mesh with the flywheel ring gear. The gear system in the starter motor is designed to transfer the motor rotation to the flywheel. As a result, the flywheel spins and provides the energy required to start the engine running.

The happenings described above occur almost instantly as soon as you close the ignition switch. The starter motor must not run for a long period, or it will overheat. In a typical starting session, it should only spin for a few seconds. That is often enough time to have started the engine. In the instances where it does not, it is advisable to wait between the ignition trials to allow for sufficient cooling of the motor.


Starting System Parts and Functions

Starting System Parts and Functions

Because the starting system is a combination of different parts, it would be good if we discussed the purpose of each. That is because a faulty part of the system can render the starter motor ineffective, or even nonfunctional. The main parts include the following.


Battery- usually a rechargeable lead-acid type, the battery supplies the necessary electrical energy to run the starting system. Most batteries are 12V but the types used in large vehicles or engines that have higher voltages, as high as 24V.


Ignition switchthe switch that allows the person driving a vehicle distribute battery power to where it is needed. It can be to the car accessories or other drive functions. In our case, the ignition switch sends power to the starting system.

Typical Ignition Cut

To power up the starting system, the ignition switch must be turned to the START position. This opens up circuits to supply the ignition circuit and the starter motor with the necessary current. The START function only lasts several seconds.


Neutral safety switchthis switch is used in modern automatic transmission vehicles. It denies the starter system current unless the transmission is in “park” or “neutral”. In a manual transmission vehicle, the switch is different and known as a clutch switch. It performs the same function, though. The switch is connected to the clutch so that the starter only works when the clutch is depressed.


Starter relay- a relay circuit basically uses a small amount of current to switch on a larger amount in a circuit. Usually, automobile starter motor systems require an enormous amount of current to work- in the order of 200 amps and above. Now, that amount of electricity would melt the wires in the ignition circuit among other parts.

An alternative would be to make these wires really thick, which would not be practical. The starter relay uses a small current from the battery to close a circuit that supplies a large current to the starter motor unit.


Starter Solenoidit is the part that is responsible for closing the circuit to supply the starter motor with current. It also pushes the pinion drive gear to mesh with the flywheel gear. The starter solenoid sits atop the starter motor to make one unit.


Starter motora small but high-torque motor that provides the kinetic energy to get the engine running. The motor requires large amounts of current, which is why the circuit that connects of to the battery has to be closed by the starter solenoid to bypass the other components. The motor consists of an armature and magnet. The magnet can be either permanent or electromagnet.

Having looked at what a starter motor is and the various parts it works in conjunction with, we can now see about the different types used in motor vehicles. There are several of them. Each as its advantages and disadvantages, as we will find out in the next chapter.

Chapter 2

Starter Motor Parts

Starter Motor Parts

The starter motor consists of different parts working together. Most of the components are mechanical and move to effect a required function. Others are electrical and serve to allow current to move through the starter. In this chapter, we will concern ourselves with the main parts of a starter motor. These are the ones that perform essential roles and which, if faulty, can mean a failed starter system.

Starter Motor Parts Names and Functions

The main parts are:

  1. The Starter Solenoid

Starter Motor with Label

 The solenoid is the tubular unit on the top of the motor. It derives its name from the fact that it contains a solenoid- wire windings to produce a magnetic field. The starter solenoid moves the pinion drive gear to make it mesh with the starter ring gear on the flywheel. This causes the flywheel to spin from the motor rotation, and the motion starts the engine.

Another function of the starter motor solenoid is to close contacts that are the power supplying circuit of the motor. When the contacts close, current flows from the battery into the motor, causing it to start spinning. This way, the solenoid acts as one big relay. These functions it performs simultaneously when the ignition switch is closed.

The starter solenoid consists of two coils; pull-in and hold-in. The pull-in coil moves the starter solenoid plunger, a rod that moves the pinion gear toward the ring gear on the flywheel. Positioned next to it, the hold-in coil serves to control the movement of the pull-in coil. The starter solenoid is a powerful device. It must provide enough force to push the pinion gear forward.


Solenoid Plunger
Solenoid Plunger

The solenoid plunger works the lever that moves the pinion drive. It is made from a strong material as it involved in the movement that pushes the drive gear toward the flywheel. It is situated next to the pull-in coil, specifically in front of it.


Solenoid Cap
Solenoid Cap

This is the solenoid cover and holds the terminals that supply current to the solenoid. The contacts of the motor circuit, too. On the cover are terminals for the cabling.


  1. The Starter Motor

The Starter Motor

This is the main part of the starter unit. It is a motor and gear combination which work to produce the rotation needed to start the engine. The parts of the motor include:

Field Coil
Field coil

It consists of wire windings that provide the magnetic field to cause the rotor coil rotation. It requires current to operate, which reaches it through terminals on the starter solenoid cap. The coil works by the process of electromagnetic induction to supply the required magnetic field from an electric current. The wires that make the field coil are copper and wound around a yoke.


Also known as the coil rotor, the armature coil is the rotating part of the motor. This component rests on bearings at both ends of the motor shaft and receives current through the commutators. It consists of a laminated iron core and with windings of copper wire going around it. As the current flows through the windings, a magnetic field is created around the armature. This causes it to rotate. The armature and field coil in starter motor windings have to be efficient enough to produce a high torque that can start the engine.


These look like partitioned copper places and convey current to the armature coil. A commutator also acts as a safety component in the event of a short circuit. These parts are positioned in front of the armature coil on the shaft.


The motor brushes connect the terminals on the solenoid cover to the motor coils.  There are usually four brushes in a starter, two negative and two positives. However, some motors will have a higher number of these brushes depending on construction and application.

Shift Lever or Fork
  1. Shift Lever/Fork

This is a fork-shaped part of the starter motor that moves the pinion gear. When the pull-in coils is energized, it creates a magnetic field that pulls the plunger to work the lever fork. The plunger connects to fork. When it moves, the fork will also move. These movements are what push the pinion gear to a position where it can rotate the flywheel.

  1. Pinion

The starter motor pinion is a combination of gears and springs that work to cause the rotation of the flywheel. That, in turn, moves the engine parts to cause it to start. It also contains a spring that pulls back the pinion gear when the ignition key is released

  1. Starter Motor Drive Gear

The drive gear meshes with the flywheel ring gear. The motor rotation then transmits to the flywheel. The flywheel is connected to the vehicle’s crankshaft, and its rotation causes the engine to start.

  1. Starter Motor Housing

Finally, there is the housing- a shell that protects the various starter motor components. The starter motor housing is made of metal. It should be sturdy enough to withstand impacts and corrosion.

The parts described here are those found in an electric starter motor. The working  mechanism, too. There are other types of starters that do not use electricity, but which perform the same function of starting an engine. The next chapter talks about the many different types of starters used in automotive systems.

Chapter 3

Starter Types


This guide mainly discusses the electrical or electronic starter. But the electrical motor starter is not the only starting unit used to crank internal combustion engines. While it is the most used in today’s automobile, there are several others that do not require electricity to function. Some are driven by air, and others hydraulic systems.

The type of starter unit employed depends on many factors, such as the amount of torque required and the type of engine. When the engine to be started is large, the starter can even be another engine. Let us look at the types of starters for internal combustion engine.


Types of Starters


Pneumatic Starter Systems

As the name suggests, these staters use air to work. Essentially, a pneumatic starter comprises a steel pressure tank, compressor pump, and rotating turbines. As compressed air escapes the tank, it provides the force to drive the turbines. Through a series of reduction gears and a pinion drive, the rotation of the turbines causes the flywheel to spin. The mechanism to engage the drive gear with the ring gear on the flywheel resembles that of the electric starter motor.

Pneumatic starters are mostly used to starts large engines, especially the diesel types. You will mostly find them in trucks and other similar heavy-duty engines, among them ships engines. They are also common in gas turbine engines such as those used in aircraft. An advantage of pneumatic starters is their reliability, simple design, and immense torque. They also do not require the electrical connections characteristic of electrical starter systems, and neither do they require batteries.

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Spring Starter Systems

These systems depend on a wound-up spring to start the engine. By turning a crank, you get the pinion gear to engage the flywheel ring gear. The turning crank also tensions the spring and readies it to rotate the flywheel. Start mechanism consists of a lever which, when releases causes the stored potential energy of the wound-up spring to produce rotation. Once the spring has finished cranking the engine, a mechanism automatically moves the pinion away from the flywheel.

Spring starters can also be cranked manually. They are most common in sea vehicles. As you can guess, these starters are highly reliable as most of their control is manual. They are also low-maintenance systems. However, their use is much limited in cars where things have to happen automatically.


Hydraulic Starter Systems

These are mostly used to start the diesel engines of sea vehicles. A hydraulic starter consists of a fluid tank, pumps, valves, and filters. Starters of this type are reliable, plus they can be used with almost any engine. Because they do not use electrical connections, hydraulic starters are free from the wear caused by sparks. The torque they produce is usually high and suitable for large engines. Hydraulic starters can also work in a wide range of conditions.


Fuel Starting Systems

This type of starter forms part of the engine. Usually found in gasoline engines, the fuel-starting system utilizes the first or several pistons of the engine to provide the force to start the rest of the engine. It does so by injecting some fuel into the starting cylinder or cylinders, then igniting it. These starters are mostly found in modern engines and those that have more than twelve cylinders.


Electrical Stater Systems

These use an electric motor to provide rotation to turn the flywheel, and the type discussed in this guide. Electric starter systems are the most common in today’s passenger vehicles for their convenience. You only need to supply them with an electric current from a battery, and the engine starts straight away. These starters are high-maintenance systems, though. The electrical circuits can easily corrode or loosen to cause the starter to fail, among other faults. Electrical starters come with a wide range of drives as explained below.


Starter Drives Used in Electric Starter Systems

A starter drive transfers turning force to the crankshaft by meshing the drive gear with that on the flywheel. This works the pistons and starts the engine. Starter drives engage the flywheel at startup and disengage when the engine starts running. Different mechanisms are used to achieve this operation. To better understand these drive designs, let us have a look at each in one of them in detail.

Gear Reduction Drive

Gear Reduction Drive

This drive utilizes a set of gears to achieve a high torque that can spin the flywheel effectively. However, that happens at the expense of speed. Gear reduction drives are among the most used in the electrical all starter systems of modern automobiles. By using gears to increase torque, small high spin motors can be used. That means reduced power consumption, which is desirable these starter motors since some can draw a lot of current.

Inertia Drive

Inertia Drive

In this type of drive, the starter motor first turns an onboard flywheel to build up sufficient momentum to turn the main flywheel. Once this is achieved, an automatic mechanism consisting of solenoids cuts of current to the motor. It also moves the flywheel to connect with the engine and start it. The person starting the engine usually performs the different operations of the starter.

The motors used in inertia drives do not drive the engine directly. As a result, a small low-power motor can start a big engine using minimal electric power. That makes them a common type of starter in some aircraft. However, these drives are slower than the other types due to the various stages and movements involved.

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Folo-Thru Drive

A folo-thru drive uses a latch and flyweights to keep the drive gear engaged and to disengage it. When the drive moves forward, the latch closes in to maintain the meshing of the gears. The latch only releases if the engine starts with the help of the flyweights. When the engine is running, the speed of the flywheel will exceed that of the motor. That causes the flyweights to move outwards, pulling the drive gear with them and causing it to leave the flywheel. This starting method ensures that the drive only disengages when the engine starts and not before.

Movable Pole Shoe Drive

Instead of the regular solenoid, this starter drive uses a movable pole shoe to push the pinion gear to the flywheel. When the ignition key or start button is pressed, current flows to activate the starter relay. That, in turn, causes current to flow through a field coil, pulling the moveable shoe. The shoe, in turn, moves the starter drive to mesh the drive gear with the flywheel.

At the same time, the movement closes two contacts to complete a circuit that sends current to the motor. The motor rotates, and a set of gears transmit the motion to the flywheel to start the engine. The pole shoe is spring-loaded. This causes of to return to its original position when the engine starts and the ignition key is released. The contacts supplying power to the motor open, the motor stops, and the pinion gear pulls away from the flywheel.

A starter motor consists the motor and starter solenoid, which are in some ways independent components. The motors used in these starters feature different starting systems, as we will see in the next chapter.

Chapter 4

Starter Motor Categories By Starting Methods

Apart from the different designs and drive mechanisms, starter motors can be grouped by their starting methods. Motor starter circuits help protect the motor from current overloads. Some contain a temperature control function that cuts current to the motor windings if there is overheating. Before taking a look at starter motors based on starting method, something about the starting techniques.


Starter Motor Starting Techniques


They are:

Full Voltage

Full Voltage

Full voltage starting involves applying full voltage to the motor. It is is the most common technique for 3-phase induction motors. Full voltage starting is also known as direct on-line or DOL motor starting. It is only used on motors that are not more than 5HP.

Reduced VoltageReduced Voltage

Unlike the full voltage method, reduced voltage starting is used for 100HP motors and higher. These are the high-current motors. The technique involves applying low initial voltage then, increasing that to reach the motor’s rated voltage once it starts to rotate.



This refers to the technique that allows the motor to rotate in both directions. The technique is useful in situations where such rotation options are necessary. A bidirectional starting method involves using appropriate connectors and mechanisms to allow rotation in both forward and reverse directions.


Multi speed

As the name suggests, this starting method enables the motor to spin or operate at more than one speed. That is achieved by using different contacts and applying different voltages. Most of these starters allow for two or three speeds.


Starter Motor Types Based on Starting Methods

Now that we have seen the various starting techniques for induction motors, let us look at the different staters based on those. They are:

Stator Resistance Motor State
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Stator Resistance Motor Starter

This starter uses external resistances to cause a voltage drop in the stator windings of the motor. A series connection is used between the resistances and the wire winding phases, and maximum resistance maintained during starting. The resistance is then removed when the motor starts to pick up speed. This allows full voltage across the windings and full motor speed.

An advantage of these types of starters is that they feature a simple design and are, therefore, cheaper to construct. A major downside is that they give a low torque when starting due to the voltage drop. The resistances used also causes unwanted power loss.

Auto Transformer Motor Starter

Auto Transformer Motor Starter

It is a type of starter that uses an autotransformer as the name hints. The transformer and the motor are connected in series, a setup that helps reduce the voltage to the motor. The voltage drop is controlled via a slider on the autotransformer. A switch allows for the voltage to be changed from low to full.

During startup, the voltage applied is low, and based on the slider position. Relays automatically change the voltage to full voyage automatically when the speed of rotation reaches more than 80% of the motor’s rating. Autotransformer starters feature a complex starting technique, which makes them more costly.

Star Delta Motor Starter

Star Delta Motor Starter

This starter uses a star connection at startup and delta when operating. The star connection lowers the voltage across the windings and reduces the current in the windings. Once the motor attains sufficient speed, a series of relays close a switch to apply full voltage through a delta connection.

Star-delta starters are among the most used. The starters are inexpensive to make, plus they are not tasking to maintain. A drawback about them is that they can only work if the motor connection is delta. Overall, star delta starters offer many advantages when compared to the other types.

Direct Online Motor Starter

Direct On-Line Motor Starter

These motors are low power rated-below 5HP. As a result, they do not use high currents and do not require voltage reduction across the windings. That means they can connect directly to the source of power, hence the name direct on-line.

DOL starters do not need the voltage reduced. However, there is the risk of motor overload that has to be prevented. A mechanism is, therefore, used in these starters to act as overload protection. It consists of thermal relays and sensors which when activated by rising temperatures, move to switch off the power supply to the motor.

Direct on-line motor starters are a simple design. That makes them the cheapest of all types. They do not feature the complicated starter techniques of other starters and are easy to care for. Their downside is the high current that they take when starting which results in a lot of energy being lost.

Soft Motor Starter

Soft Motor Starter

In this type of starter, semiconductors are used to reduce the voltage applied to the motor. Soft starters connect with the power supply in series and comprise of thyristors for every stator winding phase. As soon as the motor has picked up speed, a special circuit allows full voltage and the motor operates at its rated speed.

Semiconductors reduce voltage smoothly, unlike the other techniques. As a result, the motor does not jerk when starting. To protect the motor from overloads or low voltages, soft starters come equipped with thermal protection mechanisms.

As we have seen, starter systems can feature complex electrical and mechanical parts. This makes the systems prone to failure due to electrical circuits becoming faulty or the mechanical parts failing. Because faults are inevitable, the best thing us to stay alert on the signs. That is the topic of the coming chapter.

Chapter 5

Starter Motor ProblemsStarter Motor Problems Symptoms

The car starter contains moving components and electrical connections. That means it will inevitably wear or corrode over time. Damage does not happen straight away. It is usually gradual, giving signs all along. Identifying these signs enables you to to stop the damage before it affects starting.

With the essential function of this component, you want to catch damage and wear early enough. It would prevent situations where the vehicle refuses to start even with a new battery. How do you know if you have a bad starter? We compiled a list of the signs to watch out for.

Starter Motor ProblemStarter Motor Problems Symptoms

Some will be about the motor, others the solenoid or driveshaft and gears. They are:

  1. Odd Noises or No Sound at All

Starter motors are usually tucked away from view and cannot be accessed straight away. That makes the sounds they produce one of the easiest ways to tell if they are failing. Bad starter sounds are often varied and can include winning, grinding or even clicking noises. Here are the different sounds explained.


It indicates a bad pinion drive gear. It could be that the gear is worn, or a tooth is missing and affecting proper meshing of the two gears. Or, the problem could be with the flywheel ring gear. Grinding noise can also result from loose mounting. When the mounting bolts wear over time, they may loosen and cause the drive gear not to engage the ring gear smoothly.


This may caused by a pinion gear that does not engage with the flywheel properly, even with the starter motor spinning correctly. It can be a sign of starter solenoid failure..


A buzzing sound can be sign that the starter is not receiving enough current. The cause could be poor connections that need to be checked. It may also be a problem at the motor or other parts of the starting system. These include a weak battery or corroded terminals.


You turn on the ignition key and you hear clicks. That can indicate a bad starter solenoid or motor defective motor. A clicking sound could also be a sign of other faults in the tarting system, such as poor connections.

No sound

No sound is a sign of starter motor not spinning due to a lack of current.  Causes for that would vary, but the most common are a dead battery, corroded connectors, or bad relays and failed safety switch. It could also be a burnt out motor or starter solenoid that needs replacing.

  1. Cranking/Starting Problems

It can be slow cranking, a click with no crank, or a no click no crank situation. While these may point to poor electrical circuits or weak battery, it could also indicate a failed starter motor. Cranking problems are explained in detail below.

Slow cranking

In this situation, the starter will crank, but the RPMs it transfers to the engine are too low to start it. A slow cranking starter motor is likely to be caused by problems in the wiring that are starving the starter of current, or it could be the starter that is bad. The other causes, therefore, need to be ruled out.

Click but no cranking

it involves the solenoid clicking, but the motor failing to crank the engine. If the other parts of the starting system, such as the battery and relays are working properly, it could be a bad motor.

No click and no cranking

Here, the solenoid does not click, and neither does the motor crank. In most cases, the problem lies in the parts away from the starter. However, it could be a dead motor starter if the other components of the starting system are working.

No Sounds Problem
  1. Occasional Starting Problems

 Intermittent issues when starting your car can be a sign of starter motor not working as it should. Some days it will crank at the first attempt an on others require a few more. Should that happen, several reasons could explain the situation. It could be faulty wiring that prevents the free flow of current from the battery, or it could be failing relays. Performing tests would help identify the failing part of the starting system.


  1. Freewheeling

Starter freewheeling refers to the situation where the starter is on but the drive gear not engaged with the flywheel ring gear. You will hear the starter produce a whining sound, but the engine will not crank. Freewheeling usually results from a bad solenoid. This is the part that should produce the movement that pushes the pinion drive gear forward to mesh with the ring gear. If it is faulty, that part of the starting process will not happen.


  1. Starter Running Even After Engine has Started

Usually, you release the ignition key or start button as soon as the engine starts. That should cause the starter to stop working. If it does not, the electrical system from the battery to the starter itself could be faulty. Welded contacts in the starter solenoid could be the reason, or a fault in the circuitry. That would need to be checked immediately to avoid damage to the various components of the starter motor.


  1. Smoke or Burning Smell

When a starter motor has failed, it will likely overheat. The different parts of the starter are lubed, and excessive heat would cause the lubricant to burn and produce smoke or the smell of burning something. Should you notice smoke or burning smell, have the stater checked immediately before using the vehicle.


  1. Interior Lights Dimming During Ignition

This indicates an electrical problem. The interior wiring of the starter motor is likely shorted and causing the unit to draw a lot of current. That leaves the other electrical access without sufficient power  and the reason for the dimming.


Starter Motor Failure Causes

A starter motor will fail due to various reasons. It can be as a result of poor maintenance, or a case of normal wear and tear. To give you an idea of what could be causing your car’s starter motor starting problem, let us look at the most common reasons.

Dead battery

A weak or failed battery will not supply enough power, and the starter does not perform its function. In such case, a new battery is needed for proper starting of the engine.

Faulty circuitry

Broken cables can short the starter system and cause it to malfunction. Loose, dirty, or corroded connections, too. If the windings in the motor or starter solenoid burn out, it can mean a failed starter. Sometimes, it is about a failed switch in the relays. The motor switch at the solenoid housing may weld and cause the starter to fail.

The Dirty or worn mechanical parts

It is one of the main causes of the starter not engaging sometimes. If either the pinion gear or flywheel gear has worn or missing teeth, the drive pinion will not mesh with the ring gear smoothly. Motor brushes will also wear out cover with dirt to cause starter problems. Worn or dirty starter motor brushes symptoms include slow cranking and related issues. Other parts that can wear out include commutators and armature bushings.

Entry of oil or water

The location of the starter motor makes it prone to being soaked with oil from other components. When there is a leak, oil may spill and reach the starter motor and solenoid. That can cause it to malfunction. Water in the starter motor can also cause of to fail. It results in corroded parts and faulty electrical connections.

Entry of Oil

Loosely mounted starter

The action of the motor to start the engine involves the drive gear pairing with the ring gear. That requires that the starter unit be firmly mounted. If it is not, the meshing action may not be smooth.


Now that we know the signs of starter motor problems, how do we go about confirming and fixing them? Many vehicle owners look for quick ways to work around a faulty starter. They may research for information such as how to how to fix a stater motor with a hammer or even how to start a car with a bad starter. But is it advisable?

In the next chapter, we delve into the ways to diagnose a starter. The process described will apply to different vehicles, from the average car, truck, to tractor starter troubleshooting. Also,  we the repair of different parts such as how to rebuild a starter solenoid and starter motor components.

Chapter 6

Starter Motor Troubleshooting Methods

Staarter Motor Troubleshooting

Most starter problems can be diagnosed using simple methods. Some are also easy to fix, and may not need expert skills to handle. In this chapter, we will look at  how to fix a starter motor once you have found out the issue with it. Before we proceed, here is a list of the tools you will likely need.

  • Voltmeter
  • Spanner set
  • Pliers or side cutters
  • Socket set
  • Hammer
  • Screwdrivers
  • Soldering iron
  • Oil and rags
  • Flat working area such as a bench


Now, onto the process to troubleshoot a starter motor. This procedure applies to different starter motors as they contain similar components.

Diagnose the Promble of Starter Motor

Step 1: Diagnose the Problem

A bad starter will show many signs, such as slow or no cranking. It will also produce unusual sounds when you turn on the ignition key or start button. In cases where shorting has occurred, the electrical connections may overheat and cause smoke to come out of your car’s front. Knowing the cause of the problem can help you get the starter working again.

First, find out the problem with the electrical system. After ruling that out, you can proceed to troubleshoot the starter motor itself. The electrical system consists of the battery, cables, switches, and relays. We will, therefore, start by checking and testing those.

Because a weak or dead battery can be the reason for the starter not working, your troubleshooting process should start there. Check the battery terminals and cables. Loose, torn or broken cables mean an inadequate amount of current is reaching the starters. Corroded connections, too.

Low voltage could be another cause of starter failure. Use a voltmeter (or a load tester if you have one) to measure the battery’s voltage. If it indicates 12.6V, the battery is in good condition and the problem is elsewhere.

A sure and simple way to test your battery is using a different vehicle. If it can start the engine of another car, the fault is likely with the starter motor. In that case, you can proceed to the steps to fix a bad starter motor.

If the battery terminals are corroded or the cables are loose and broken, disconnect and clean them. Or if badly damaged, replace them. You will also need to replace a weak or dead. Check the rest of the cables and connections to see if there are signs of breakage or corrosion. Simply cleaning or replacing faulty connections can restore current flow. Once satisfied with the state of the cables, you can proceed to step 2.


Step 2: Remove the Starter

Remove the Starter

NB: Before starting any repair actions, disconnect the battery connection by detaching the cables. The current that flows through the connections to the motor are extremely high, reaching above 250A, and could cause serious injuries.

Locate the starter motor. In most case, it can mean having to lift the car. Do that safely, using appropriate equipment. Next, remove the starter by unfastening the mounting bolts. It should come out without any difficulty.


Step 3: Disassemble the Starter


Once the starter is out, it is time to take it apart and check the various components. Find a clear surface to do so, such as a clean bench. Have with you a container to put the small bits such as screws and bolts. The starter motor will likely be covered in dirt. Use a rag soaked in petrol to clean it.

Be sure to mark the parts so you can avoid confusions when re-assembling the unit. Next, strip the starter using the following sequence.

  • Using the appropriate screwdriver, take out the screws on the back cover to remove it. They are usually two small screws that will come out easily
  • Find and detach the clip and spring, and the heat shield
  • Locate and disconnect the motor cable from the solenoid
  • Next, remove the main bolts in the starter. These are the long boots that hold the housing together
  • Take out the brush cover and unclip the brushes to remove them. The brush holder, too.
  • Take out the field windings, both the stator and rotor
  • Unfasten the bolts on the solenoid and remove the internal components without disassembling them


Step 4: Inspect the Parts

Inspect the Parts

Arrange everything on the bench. Examine the different component to see how badly they are damaged. Check the stator and rotor windings for broken wires or stripped insulation. The commutator and armature, too, for defective parts. Look out for wear on the mechanical components such as the pinion gear, solenoid, brushes, and others.


Step 6: Windings and Starter Armature Repair

These parts will likely be corroded. Sand them to remove the corrosion. Clean the areas between the segments. After you have cleaned every surface, use an oiled rag to wipe the components.

If there are darts that cannot be used anymore due to damage, you will have to replace them. That means buying new ones and fitting them before re-assembling and mounting the starter. Brushes wear out quickly, and there is a high chance that they will need replacing.

If that is the case, obtain new ones and fit them as appropriate. You may need to observe how the old ones are installed to ensure proper fit. Other parts that may require replacing include bushes, commutators, and the armature. If there are no components to be changed, proceed to the next step.


Step 7: Re-assembling the Starter

It is now time to back everything back in its place. If you had marked the various parts, that should be easy. Use the reverse of the process to take it apart. Everything should fall into place.


Step 8: Bench Test the Starter

Benchmark Testing

You will need to test the starter before installing it. This will ensure that it is working properly- a clear indication that the assembly was done correctly. For this, you will need a working battery and some jumper wires. Then, perform these tests.

    • Motor test- with the negative cable of the battery connected to the stater housing, touch the bottom terminal on the solenoid with the positive lead. The motor should spin fast.
    • Starter solenoid test- with the negative battery lead on the housing of the starter, touch the small terminal post on the solenoid with the positive lead. This should activate the solenoids to move the plunger and push the drive gear forward.
    • Motor-solenoid test- connect the battery’s positive cable the top terminal on the solenoid. There should be no response in the motor. Next, touch the small terminal post with another posits lead. The whole unit should work normally; switch the solenoid pushing the rod that moves the drive gear and the motor spinning at high speed.


Step 9: Mounting the Starter Motor

Next, mount the starter. That means simply bolting it to the engine block. Use the right torque for that, or it will loosen over time and cause starting problems.

In most cases, starter motor or starter solenoid rebuilding may not be advisable due to excessive damage. You may need a new one installed. That would mean having to shop for a starter if planning to do it yourself. Next, we look at how to buy the right starter motor for your vehicle.

Chapter 7

Starter Motor Buying


When you have a bad starter motor, you can fix it by repairing the faulty parts. If the faults are beyond repair, it can mean having to replace the whole unit. Replacement comes with its challenges. There are different types of starter motors in automobiles, with different designs and sizes. Configurations, too, and mounting methods. These components are costly, and you want to get it right the first time. In this chapter, we will look at the factors to take into account when buying a starter motor.


Starter Motor Selection

When looking to a purchase starter to replace a failed one, consider these requirements. It will help you find the right starter for your vehicle. Also, a quality one since it will satisfy the power needs of your specific engine, among other aspects.


Starter Motor Number

Checking on the number part

The number on the new starter motor needs to be similar to that on the old starter. That prevents compatibility issues such as mountings style, power requirements, and more. The starter motor number is usually written on the body of the unit. The exact location of the number varies across the starter makes and models. However, it presents no challenge to find.



This refers to the ability of the starter motor to spin an engine. When selecting the model to buy, ensure the torque is high enough for your particular engine. The motor will not overheat during the starting process to cause problems. The torque output you choose will depend on the compression ratio of the engine. Generally, a 200 ft lb starter motor works for the typical car using a 12:1 compression ratio engine or higher.

Voltage Requirements

Different starter motors require different voltages to operate. The level of voltage usually directly determines the torque achieved by the motor. The voltage you select should match the compression level of the engine in most cases. There is the lowest voltage level that a specific starter would need to have. You would need to ensure the one you buy can handle your type of engine.


Casting Material

Starter motors undergo a lot of stress to start an engine. If the engine is high compression, it can mean a starter that works too hard. There is also the issue of kickback possibilities. If the motor is not strong enough, it can result in the housing falling apart. There is also the problem of physical impact given the position of the motor on the underside of most vehicles  As such, the starter should be made from cast metal of the highest quality. You want it to last for long, even when used in harsh conditions.


Internal Components

Internal Component

Apart from the outer casing, there are internal components to consider. Starter motors are usually mounted low, which makes them prone to the elements. It is often common to have inner components that are damaged by the corrosion caused by the entry of water. Sometimes, it is a case of parts that wear out too soon due to inferior materials used to construct them. Ensure the materials used are of high quality. Mostly. Steel components last a long time, and you want that for your starter motor.

Size and Weight

Manufacturers usually try to make starter motors that are compact and lightweight. Compact units make fitment easy, while light starter motors help to reduce the overall weight. For whichever reason, you may want a compact and lightweight starter. Do not compromise that for power, though. Ensure the motor can crank your type of engine and higher, or you will have a new compact and lightweight starter but which will not start your engine.



While there are new manufacturers who will produce quality products, you may want to choose a brand that guarantees you quality. Such brands have happy previous customers. You may use their comments to choose your starter motor. A trusted manufacturer will also likely offer generous warranties for their starter motors.


Type of Drive Used

While the starter motor working principle does not change, pinion drive mechanisms do. The method used to transfer motor rotation is one of the essential considerations when choosing the starter to buy. Often, gear reduction motors offer better starters. You can have a small motor but whose power multiplies greatly to crank a high-compression engine. These types of motors produce a high torque. Gear reduction starters are also mostly compact. This makes them easy to install when space is an issue.


Motor Starting Method

Motor Starting Method

As explained previously in this starter motor guide, starters feature different pinion drive mechanisms. Because motor starting methods vary widely, you would need to choose the type that matches your power requirements. If your engine is low compression, a direct on-line motor would be suitable. Starters of this type are the cheapest of all and their motor easy to maintain


Aftermarket Vs. OEM Starter Motors

When buying a starter motor, you will be faced with two options: an aftermarket unit and an OEM one. Each type will have its up and downsides. OEM starter motors do not come in many variations, which makes selecting the right one for your car easy. However, these starters are often more expensive.

Aftermarket starters can be high quality, sometimes higher than the aftermarket versions. A disadvantage of these starters is their wide range that makes finding the right one for your engine type difficult. If you are not careful, you may end up with an incompatible aftermarket starter motor. Overall,  aftermarket feature many and useful characteristics.


Common Questions When Buying and Replacing a Starter Motor

 There are many, and we answered the most asked.

Question. How much does it cost to replace a starter motor?

Answer. Starter motor cost depends on type, drive mechanism, and starting technique. It also varies across different vehicle types and makes. The wide variation makes of difficult to point an exact amount. However, expect the cist to be mostly above $500 for both new part and labor to install. Starter motor repair cost should be much lower than that since no new starter is used. But the amount varies depending on the parts being replaced or the complexity of the problem.


Question. How do I find a starter motor repair near me?

Answer. Finding a trusted repair shop or individual can be difficult. Despite that, an online lookup will usually reveal the ships in your locality, and you can choose the one to go to based on reviews. You can also depend on the word of mouth by asking around from close friends or even relatives.


Question. Is it better to replace the whole starter if faulty?

Answer. It is highly advisable to do so. However, that would largely depend on the kind of fault. It would be illogical to replace a whole starter whose only problem is a loose or corroded connection. That is especially if the other starter system components in both the motor and the solenoid are in prime condition. It also depends on your budget. With replacement costs running above $500, it would make economic sense to fix faults rather than install a new unit.


Question. How difficult is it to replace a starter motor?

Answer. Without having to fix anything, the process the install a new starter should be one of the easiest in a vehicle. It involves removing the old unit and installing a new one. You will only have bolts to unscrew and fasten.



The automotive starter motor is one of the main components in the car starting system. A faulty can mean a car that will not start. That is why ensuring its proper working is essential. After reading through this starter motor guide, you can now take care of the starter better. You understand how it works, the different types there are, and how each functions. The guide also describes the symptoms that show a failing starter so you can take action early enough. With early diagnosis, you can avoid costly replacements.

You will, at one time or another, have a bad starter and face the option to repair or replace it. We included a part to help you with that. Starter motor replacement means having to buy a new unit. The last chapter aims to help you choose the right type for your vehicle. The best quality, too, by knowing the features to look for. It is a guide that contains information to ensure you do not ever get stranded due to a failed starter motor.

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