The starter motor is an important component in a car’s ignition system. Your battery sends the amps required to start a car to this motor which, in turn, cranks the rotating assembly for ignition.
If you’re looking for a new car battery, it’s important to know the starter amps of your vehicle. So how many amps does a car starter draw? Check out the answer below.
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The Average Amps Draw of Each Type
The amperes needed to start a car depend upon various factors like the outdoor temperature and oil quality. The size of your engine is also a significant indicator of the starter motor amp draw. In short:
- 4-cylinder vehicles need approximately 200-960 amps
- 6-cylinder vehicles need approximately 250-1200 amps
- 8-cylinder vehicles need 300-1680 amps
- Larger vehicles or trucks can require up to 1500 amps or more
How Does a Starting Motor Work?
The starting motor has a few key components:
- Armature
- Commutator
- Brushes
- Solenoid
- Pinion
- Plunger
- Field coils
- Lever fork
Simply put, a starter motor converts electrical energy in car battery to mechanical energy. Putting your key in your car completes the ignition circuit, creating a starter solenoid current draw that works to move the pinion gear and the flywheel.
The battery in your car requires a specific amount of current to send to your starter. This is measured in amps, which is short for amperes. A simple ampere unit breakdown is that it’s a measure of the amount of electrical charge that a current carries in 1 second.
When the starter’s pinion wheel engages a gear in your flywheel, the engine starts. Fuel and air then begin to enter and start the ignition.
Starter Amp Draws for Different Engine and Fuel Types
Here is a starter amp draw chart you can refer to for different types of engine.
1. Minimum number of amps
| No. of Cylinders | Gasoline Engine | Diesel Engine |
| 4-cylinder | 200A | 400A |
| 6-cylinder | 250A | 500A |
| 8-cylinder | 300A | 700A |
2. Amps needed in cold weather
| No. of Cylinders | Gasoline Engine | Diesel Engine |
| 4-cylinder | 480A | 960A |
| 6-cylinder | 600A | 1200A |
| 8-cylinder | 720A | 1680A |
Factors That Determine Amp Requirement
1. Temperature and engine type
The temperature has a significant effect on your car’s amp requirements. The amount of power your battery can deliver while starting your car under moderately cold weather is indicated by your cranking amps.
Typical cranking amps are rated for electrical current discharge at 32℉ or 0℃ for 30 seconds. Temperatures lower than this make your batteries’ chemical processes slower, resulting in more cranking amps needed to start a car, which is why people have come up with a unit called cold cranking amps to measure battery performance.
You also need more amps to start a diesel engine than a gas one because the former has no spark plugs.
Note: While looking at starter amp draw specs, you may also see cranking amps vs peak amps. Peak amps are the highest output a starter can generate, unlike cranking amps, which are the sustainable, lower current discharge measured over a period of time.
2. Oil thickness
The viscosity of your oil can impact the efficiency of your starter amperage draw. Thicker, more viscous engine oil is heavy and makes turning the engine more difficult. You would need to draw more starter amps from your battery as a result.
Cold oil can be thicker as well. This strains the battery, and the amps to jump start a car increase significantly.
Good quality oil is not only better for your engines but will also help your starter work more easily.
3. Condition
The condition of your car starter is another important factor when considering the amps to start a car. When corroded, the starter solenoid draw can be limited. A rusty starter motor or poor battery cable will have trouble conveying energy.
Keeping your starter motor clean and rust-free by conducting repairs or replacing them can keep your car free of problems.
4. Battery voltage
Another factor that affects the amps needed to start a car is voltage. Voltage is a unit of measure that determines how much pressure is applied to make energy flow.
A 12 volt motor draw is 600 amps and is the standard battery size. When a car battery reaches 12.6 volts or more, it is considered to be at 100% capacity. A slight decrease in the battery’s voltage can impact how well it performs.
When the battery is discharged (at 12.39 volts or less) or at low power, it would not put out the voltage needed to activate the ignition system.
5. Engine size
When asking the question of how many amps does it take to start a car, the first thing you need to know is the size of the engine. There is a direct correlation between the two as the larger the car or engine gets, the more amps are necessary to start it.
One of the main reasons why larger engines need more amps is that they have more components. The number of cylinders is one of the significant parts of this.
The compression ratio is another part of the engine that can affect your starting amps. Compressing raises the air temperature high enough so that it can ignite the fuel, and a higher compression ratio means more current.
Symptoms of a Car Starter Problems
Starters can last for a very long time. However, there may come a point where they begin to fail or stop working. Knowing the signs of a failing car starter can help you assess the damage and is the first step to troubleshooting.
1. The engine won’t turn on
This is an obvious one. But if you turn your key and you hear no cranking or just a clicking noise, there are two possibilities. Either you have an issue in your key system or in your starter’s solenoid.
2. Dimming interior lights
An electrical wiring issue might be present when interior lights and the dashboard begins to dim when the car use at idle.
3. Smoke or burning smell
A big part of the starter is its electrical system. When there is a short circuit or other electrical issues, you might smell smoke from your starter. Get it checked immediately.
Troubleshooting Your Car Starter
The first step to test if a starter is bad is ensuring the car battery is fully charged and the engine is at normal operating temperatures. A battery with low voltage might show a higher starter draw.
Also, make sure that the cables and terminals are in good condition. This would rule out starter issues caused by low battery voltage. Use a voltmeter and ammeter and follow the instructions below:
- Unplug all four ignition coils so that the engine does not start while you’re checking the starter.
- Connect the voltmeter clamps on the battery’s positive and negative terminals.
- Put the amp clamp of the battery load tester around the positive or negative cable.
- Crank the motor and take note of the amperage and voltage.
- Check your car’s manual for your starter draw test specifications and see if your measurements match them.
If the engine cranks slowly but draws excessive current, there is a problem with the starter. This is most likely caused by faulty starter brushes, an engine blockage, or broken insulation.
A low cranking speed, with a low current draw but high cranking voltage would indicate excessive resistance in the starter circuit. This is caused by problems with the electrical sockets or wires.
Frequently Asked Questions
How Many Amps to Start a V8?
A V8 engine is made up of 8 cylinders and would require a lot of power to start. For gasoline V8s, the minimum amount is 300A and for diesel, it is 700A. If the engine is cold, a V8 would need around 720A for gasoline and 1680A for diesel engines.
How Many Amps to Jumpstart a V6?
A V6 engine is made up of 6 cylinders. For gasoline V6s, the minimum amount is 250A, but for diesel, it is 600A. If the engine is cold, a V6 would need around 600A for gasoline and 1200A for diesel engines.
How Many Watts are Needed to Start a Car?
Modern car batteries are 12-volt 105 AH and can deliver 1.26 kWh. Most vehicles would need at least 1kW or 1,000 Watts to start up and move as quickly as possible.
Is 300 Amps Enough to Start a Car?
If you have a medium or small vehicle, 300 amps could be enough for your car starter. However, for colder weather, I would consider 500 amps enough for 4 cylinder gasoline engines but not bigger ones.
Will 50 Amps Start a Car Battery?
Probably not, as even small cars need 200 amps to start, but you can use 50 amps to charge your vehicle batteries within 4 to 8 hours, depending on its size.
Can a Starter be Tested?
Tests can be run on your starter to determine if there are problems. You can check the solenoid with a circuit tester and use jumper cables to assess the motor.
Conclusion
Understanding the purpose of the car starter and how it works can help us diagnose and troubleshoot the problems it might have.
You should also keep in mind the different factors that can affect your car’s starter amps. Knowing how temperature, fuel, and engine type affect your starter the next time someone asks you “How many amps does a car starter draw?”
