13 Minutes Read
A car starter motor is an electrical device used to start the engine. It works on the principle of converting electrical energy to mechanical energy.
The car starting system operates the starter motor to crank the engine. A Starter consists of two parts, a solenoid, and a starter motor. The solenoid is an accessory placed on the top of the starter motor assembly that works as a relay to connect and disconnect the starter motor from the car battery.
The starter motor assembly creates a large amount of torque to spin the flywheel to start the engine. If a car engine does not crank due to a starter. It means the starter has a problem. To find out the problem, the starter motor must be tested.
Fortunately, you are on the page where the starter motor different types of tests are explained easily, and in understandable language that anyone can perform quickly within 15 minutes with pictures without under the supervision of an expert.
On this page, you will find starter motor different types of quick DIY tests and their troubleshooting while the starter motor is fitted on the car and outside of the car on the bench including starter voltage drop test.
- How To Test A Starter
- Starter Voltage Drop Test
- Bench Testing A Starter
- How To Test A Starter With A Multimeter
- Test No 1: Bench Test Starter Motor And Solenoid
- Test No 2: Bench Test A Starter Without Solenoid
- Test No 3: Starter Solenoid Bench Test
- Test No 4: Starter Motor Resistance Test With Multimeter
- Test No 5: How To Test A Starter Solenoid With A Multimeter
We will divide the page into two sections.
In the first section, we will test the starter motor fitted on the car, and in the second section, we will test the starter motor off the car on the bench. The following are the two sections of the test.
1st Section: Test Starter Without Removing It
- How To Test A Starter
- Voltage Drop Test
2nd Section: Starter Motor Bench Test
Test No 1: Testing Starter Motor And Solenoid
Test No 2: Starter Motor Test
Test No 3: Solenoid Test
Test No 4: Starter Motor Resistance Test
Test No 5: Solenoid Continuity Test
1st Section: How To Test Starter Without Removing It (Fitted On The Car)
How To Test A Starter
The car starting system can have many problems. You cannot consider the same problem for the same reason. A car starter motor can give the same problem for multiple reasons. To find the exact problem, the starter motor must be tested properly.
Below are the procedure and step-by-step tutorial on how to check if the starter is bad without removing it, when it is not cranking.
Normally, when you want to crank the car and hear nothing, it might be due to the following reasons.
- Dead Starter Motor
- Blown Fuse or Relay
- Dead Battery
- Corroded Terminals or cut in the Starting Circuit
- Neutral Safety Switch
- Anti-Theft Immobilizer
Before we troubleshoot the starter motor, it is important to check the starter motor fuse and relay. A blown-fuse and relay can prevent the starter motor from running. Similarly, observe the battery condition and corroded terminal. A fully charged battery is considered 12.6 or higher volts. A lower battery charge or corroded terminal can also be the reason for not cranking the starter motor.
Furthermore, a bad neutral safety switch or anti-theft immobilizer does not let the current flow to the starter motor. So, here you have checked all the factors, and we assume that all the factors are correct and fine without the starter motor. Now it is time for the starter motor to be tested without removing it.
Before we go ahead and start troubleshooting, it is important to acquire safety precautions. Keep loose clothing and long hair away from moving parts, and don’t allow the children near the car while working.
Tool You Need
We require a digital voltmeter or test lamp to check the starter motor.
Step 1. Check The Voltage At Solenoid Control Terminal
First of all, check for the voltage with a voltmeter at the smaller control “S” terminal on the solenoid.
Turn the multimeter indicator to the volt mode of the 20v scale, and place the black lead of the voltmeter on the case of the starter motor, and the red lead probe on the solenoid control terminal.
When you turn the ignition key to the start position, there should be voltage present at the ignition switch control terminal.
If not, then check for the following components.
- Solenoid control circuit
- Starter fuse
- Starter relay
- Ignition switch
- Neutral safety switch
- Anti-theft immobilizer
Step 2. Check The Voltage At The Solenoid Feed Terminal
Now put the same red lead of voltmeter on the solenoid feed terminal (input heavy terminal), and the black lead still remains the same on the starter motor case.
You will measure the full battery continuous voltage on the solenoid feed terminal, which comes directly from the battery positive power source or some vehicles use a heavy large size fuse.
If the 12-volt power source does not reach the solenoid feed terminal, then check for the following components.
- Lose connections
- Break in the cable
Step 3. Check The Voltage At The Solenoid Output Terminal
In this final step, you have to check the voltage of the solenoid output terminal.
Have a helper turn the ignition key and look at the solenoid output terminal voltage. It should be a full battery voltage. The feed terminal and output terminal works as a bridge that transfers the voltage from the battery to the starter motor. Now here is the possible interpretation of the outcome.
Possible Outcome No 1
If the voltmeter gives the reading of full battery voltage at the solenoid output terminal it means the solenoid is fine. Because the solenoid transfers the current from the solenoid feed (Input) terminal to the output terminal.
If the voltmeter does not give the full reading voltage at the solenoid output terminal, it means the solenoid is bad and needs replacement.
Possible Outcome No 2
Now, while a 12-volt battery power source is present at the solenoid output terminal, the starter motor should spin, so it means the starter motor assembly is ok.
But if the starter motor does not rotate despite the solenoid output terminal receiving the current, so it indicates a dead starter motor and you have to fully remove the starter motor from the vehicle. Thus, in this way, you can troubleshoot a starter motor not cranking by using a voltmeter.
You can also safely use a test lamp instead of a voltmeter if a voltmeter is not available. I will not increase the word count of my article by repeating the above steps with the replacement of the word test lamp instead of the voltmeter.
The steps and procedure of troubleshooting a starter motor by using a test lamp are the same as using a voltmeter. In the above steps, you can simply replace the test lamp instead of the voltmeter, and repeat the steps. It is simple. It is not rocket science. Don’t be overwhelmed.
And finally, you have seen that the test was so easy that anyone can perform it safely in less than 15 minutes.
Starter Voltage Drop Test
Have you experienced when you want to start the car, your engine cranks slowly but does not start. However, by testing the battery and starter, both are perfect.
The answer is, it is due to resistance, the starter motor receives a little amount of voltage than what is required, and the voltage drops across the current path from the battery to the starter.
Voltage drop test is mostly overlooked while troubleshooting a starter motor circuit. It is the most reliable test. With the help of this test, you can diagnose the component or connection with high resistance without disassembling the parts.
As you know, every component is designed to operate on a certain amount of voltage, if the voltage is lower than the required voltage will affect the performance of the component.
With the passage of time, electrical connections, terminals, cables, and contacts become corroded or rusted resulting in a production of excessive resistance in the circuit.
Voltage Drop Explained
Voltage drop refers to the amount of voltage lost when it is flowing through a circuit. It is the difference between the voltage present in the battery and the voltage at the starter motor.
The voltage drop is caused by excessive resistance present in the wire due to undersized cable or poor connections. As a rule, every conductor has some level of resistance, which is thought-out normal.
Similarly, copper is the conductor that has the least resistance amongst all other conductors that’s why it is mostly used in the motor armature. When the current flows in a wire, it feels resistance, which causes to loss of voltage.
So, a little bit of voltage loss (Drop) is normal in a circuit; there is no universal specification for voltage drop in a circuit. Every car manufacturer has its own specification about voltage drop, but most manufacturers agree on voltage drop up to 0.5 volts considered normal and standard.
Also, the voltage drop test is a great diagnostic test; it is a fast, reliable, and accurate way to deal with many electrical problems in a car especially, a Cranking-No-Start problem.
This is an Info
Every car manufacturer has its own specification about voltage drop, but most manufacturers agree on voltage drop up to 0.5 volts considered normal and standard.
What Causes Voltage Drop In Car
Voltage drop can be caused by many reasons.
- Damaged or corroded cable increases the resistance of the circuit.
- Wrong sized cable or smaller gauge cable
- Loose or corroded ground straps
- Damaged battery terminals
- Corrosion inside the cable
Tool You Need
While doing the starter motor voltage drop test, the only tool you need is a digital voltmeter (DVM). Set your voltmeter scale on 20v DC volts.
Things To Remember Before Voltage Drop Test With Multimeter
Before you start the voltage drop test, it is important to verify that the battery is fully charged. The starter motor draws a huge electric current in the car. It cannot run on a weaker battery.
Take the voltmeter and test the battery voltage. It should be 12.6 or higher volt. A 12.6 or higher volt battery is considered a fully charged battery. 12.4 volts, the battery is at 70% plus charged, and at 12.1 volts, the battery is 30% charged. So charge the battery before carrying the test.
Remember this point, if you have charged the battery on a charger. It might have a surface charge, which is not a good thing, and can rapidly discharge which might make you confused with a dead battery.
To remove the surface charge, turn ON the headlights for one minute, then turn it OFF and wait for five minutes to stabilize the voltage.
The second thing you need to do is to disable the ignition system so that the engine will not start. For your kind information, we only want to crank the engine, not to start the engine. Remove the fuel pump relay or something not to start the engine.
And remember, a voltage drop test can only be performed on a live circuit. The current must be flowing in a circuit to test the voltage drop, and this can only be achieved when the driver is attempting to crank the engine.
In the voltage drop test, the voltmeter leads are placed in parallel with the circuit being tested. Below is the step-by-step procedure of the starter motor voltage drop test. You can use the same procedure for testing the voltage drop of the other components such as the alternator, fuel pump, etc.
In the starter motor voltage drop test, we will also test both sides of the starter motor, the power, and the ground side.
This is an Info
The voltage drop test with a multimeter can only be performed on a live circuit.
This is an Info
The battery might have a surface charge due to charging, turn ON the headlights for one minute, then turn it OFF to remove the surface charge.
Procedure Of Voltage Drop Test With Multimeter
- First of all, record the “Base” voltage reading of the battery, which will help us in the future by comparing the voltage at the starter motor terminals.
- Connect the voltmeter positive (red) lead to the battery positive post (remember to connect with the battery post, not to the clamp as it can be loosely attached and can increase the resistance).
- Connect the voltmeter negative (Black) lead to the battery negative post.
- Now crank the engine for 10 to 15 seconds and note the voltage reading at the voltmeter. This is your base voltage reading.
- ow attach the voltmeter red lead with the starter motor feeding terminal stud (not the wire) and black to the starter motor casing.
- Now crank the engine for 10 to 15 seconds and record the voltage at the voltmeter screen.
- Now compare both voltage readings, the voltage reading at the starter motor and the base reading at the battery posts.
- If both readings are within specification, I mean the same or a voltage difference is up to 0.5 volt. It means the connection is good, and there is no excessive voltage drop present on the starter motor circuit.
- But, if in case, the voltage drop is higher than the normal 0.5 volts during the test, it means you have some unwanted resistance in the starter motor circuit. Now to find out the actual spot of resistance.
- For this purpose, you have to perform the voltage drop test at both circuits of the starter motor, the positive side, and the ground side.
Testing The Voltage Drop Of The Positive Side Of The Starter Motor
- Connect the voltmeter positive lead (red) to the battery positive post and the negative (black) lead to the starter motor feeding (input) terminal.
- Now crank the engine for a few seconds and note the voltmeter reading.
- If the meter reading is 0.5 volt or less than 0.5 volts, it is considered normal. The power side of the starter motor is working properly.
- But, if the meter reading is more than 0.5 volts, it means the resistance is high.
- You can pinpoint the spot where is the resistance is high by moving the meter leads closer to each other along the power side of the starter motor circuit little by little until you reach the actual spot where the voltage drops to normal.
- Remember the area where it drops the resistance after the actual spot of resistance, does have an actual voltage drop.
Testing The Voltage Drop Of The Ground Side Of The Starter Motor
- Connect the voltmeter positive lead (red) to the battery negative post and the negative (black) lead to the starter motor case (a clean spot).
- Now crank the engine for a few seconds and note the voltmeter reading.
- If the meter reading is 0.5 volt or less than 0.5 volts, the engine ground strap is in good condition, and the ground side of the starter motor is working perfectly.
- But, if the meter reading is higher than 0.5 volts, it indicates the resistance is high.
- Then check for the starter motor mounting bolts. Mounting bolts should be tight and should have a good ground connection with the engine block, and also make sure there is no dirt or grease between the starter motor mounting bolts and engine block.
Bench Testing A Starter
How To Test A Starter With A Multimeter
In this section, you are going to learn starter motor bench tests with a multimeter with no load free-running, where the starter motor is fully removed from the car.
A starter motor has a huge role in starting a car. Like other car parts, it can also wear out and losses its job. If a car does not start and you hear nothing while trying to start the engine, and also the starter circuit seems to be ok then, it might be the problem with the starter motor.
Testing a starter motor is necessary for cranking the engine. The first thing you need to do is to completely remove the starter motor from the vehicle, disconnect the starter circuit’s wiring, unbolt it and place it on a non-conducting material like a wood bench.
Make sure to remove the jewelry from the hand or any other conducting material not to cause a short circuit. Hold the starter motor firmly in a vice or have a helper place the foot on the starter motor while testing, it can jump around crazily if not held firmly.
Tools You Need
Two jumper cables, Digital multimeter, Alligator clip, Full charged battery, and a vice (Optional).
Test No 1: Bench Test Starter Motor And Solenoid
Below is the step-by-step procedure of the starter motor and solenoid bench test.
Step 1: Connect The Red Jumper Cable
Take two heavy jumper cables, red and black, and put one end of the red heavy jumper cable to the battery positive terminal and the other end to the starter motor heavy feeding terminal stud.
Step 2: Connect The Black Jumper Cable
Similarly, put one end of the second black heavy jumper cable to the battery negative terminal and the other end to the starter motor case.
Step 3: Connect The Alligator Clip
Now put one end of the smaller gauge alligator clip to the battery positive terminal and the other end to the starter motor solenoid control terminal. Here now, you will observe two possible outcome interpretations.
Outcome Interpretation 1
If, the pinion gear spins but does not move forward. It means the starter solenoid is bad. Because the motor is doing its job, which spins the pinion gear but, the solenoid is not working properly, which does not move forward the pinion gear.
Outcome Interpretation 2
If the pinion gear moves forward but does not spin. It means the starter motor is bad. Because the solenoid is in good condition, which moves forward the pinion gear but, the starter motor is dead, it does not rotate the pinion gear.
Test No 2: Bench Test A Starter Without Solenoid
In this starter motor bench test, we will discuss the procedure of testing the starter motor on the bench. We need the following tools to perform the test.
Two heavy jumper cables and a Strong battery.
Step 1: Attach The Black Jumper Cable
Attach one end of the black jumper cable to the battery negative terminal and the other end to the starter motor case.
Step 2: Attach The Red Jumper Cable
Correspondingly, attach the one end of the second red jumper cable to the battery positive terminal. And the other end to the starter motor output terminal stud (the terminal which goes to the starter motor assembly from the solenoid).
Now here are the Possible Outcomes. The pinion gear should spin (without moving forward). If it does not spin, it means the starter motor is bad.
Test No 3: Starter Solenoid Bench Test
In the starter solenoid bench test, we will only discuss the procedure of testing the solenoid. We need one jumper cable, a fully charged battery, and an alligator clip.
Step 1: Connect The Jumper Cable
Place one end of the heavy jumper cable to the battery negative terminal and the other end to the starter motor case.
Step 2: Connect The Alligator Clip
Put one end of the alligator clip to the battery positive terminal and the other end to the solenoid control “S” terminal.
Now here is the Outcome Interpretation. If the pinion gear moves forward, it means the starter solenoid is good. And if the pinion gear does not move forward, it means the starter solenoid is bad.
Test No 4: Starter Motor Resistance Test With Multimeter
In this test, an ohmmeter is used to know the condition of the starter motor. We only need Ohmmeter to perform the test.
Before I proceed further, I want to give a little touch about ohmmeter. Look, Ohmmeter reads the resistance of the open circuit by “OL” which means the Open-Loop or Open Load. The “OL” represents that the circuit is open and does not have connectivity.
On the other hand, the ohmmeter reads the “Closed Circuit” in numerical values of zero or near zero. I hope you got the idea. Now come to the test procedure.
Step 1: Put The Leads In Multimeter
Put the black probe in the common socket and the red probe in the Ω omega socket in the multimeter. Also, turn the multimeter ON and set the dial range to the lowest resistance range on ohm mode.
Step 2: Attach The Leads With Starter Motor
Put the black lead of the ohmmeter on the starter motor case and the red lead on the starter motor output terminal located on the back of the solenoid cap.
Now here is the test result. If the ohmmeter reading is of zero or some values around zero. It means the starter motor is good. If the ohmmeter gives the reading of “OL”. It means the circuit is open and the starter motor is dead.
Test No 5: How To Test A Starter Solenoid With A Multimeter
In this starter solenoid, we will bench test the starter solenoid continuity with a multimeter, we will check the continuity of two heavy terminals located at the back of the solenoid cap.
Normally, without energizing the solenoid, the two terminals of the solenoid should be opened and it is considered a good working solenoid. However, by giving a power source to the solenoid, it should close these two heavy terminals, and the current starts to flow to the starter motor. In simple words, you can say these terminals work as a bridge between the solenoid and motor assembly.
Remember the battery power should not be given to any terminal while performing this test.
Tool You Need
We need the multimeter to perform the job.
Step 1: Switch To Continuity Mode
Switch your multimeter to continuity scale or radio wave symbol on the multimeter. And do a quick test to prove the continuity mode is working by joining both leads together to hear a beep sound.
Step 2: Attach The Leads With Starter Terminals
Place the tip of both leads of the multimeter on both heavy terminals of the solenoid.
Now here is the test result.
By attaching both leads to the solenoid terminals, If the multimeter does not produce a beep sound. It means the solenoid is good. If it does produce a beep sound, it means the solenoid is bad.