How Well Do You Know Your Car's Electrical System?


By: Steven

6 Min Quiz

Image: Shutterstock

About This Quiz

We bet you don't think much about it until something stops functioning. Yup, we're talking about your car's electrical system. Do you know enough about the way it works to ace this quiz? We challenge you to answer every question correctly.

You know that your car has an electrical system, but do you really know what it does? The basics of the system are that your car's battery provides power to the starter. Then, while your car is running, the alternator gives the battery the juice it needs to keep the sparks flowing. 

Eureka, so that's why my dad told me to drive my car around for a while to charge the battery after he had to jump it that time I left the interior lights on!

And, just like the electrical system in your house, your car's electrical system distributes that electrical juice to the parts and components that use electricity to work. If only one piece of the system fails along the route, you're in trouble, and you just might be sitting on the side of the road waiting for a tow truck.

So, do you know enough about your car's electrical system to pass this quiz? Let's find out.

What are the holes where the spark plugs sit often called?

If you want to pull the spark plugs out of your engine, you'll need a special extension on your socket wrench. It needs to have a soft component to not break the plugs, and must be long enough to reach them.


Does it matter the order of your ignition wires?

Automakers actually make the ignition wires different lengths to help take the guesswork out of where each one goes. Your spark plugs don't all fire at the same time, so you need to match the correct plugs and wires, or your engine will run rough, if at all.


What does it mean if your spark plugs are covered with an ash-like dust?

You can tell a lot by pulling your spark plugs. The ashy substance might be caused by an oil leak, like what happens when your head gasket blows. Although not as likely, it might be from bad fuel, which means you should go to a better gas station in the future.


What does black buildup on your spark plugs mean?

Black, sooty buildup on your spark plugs is usually called dry fouling by mechanics. It usually means your engine is burning rich. If that's what you see, check the air cleaner to see if it's clogged, because that's likely the cause, and that's a super simple fix to take on yourself.


What is wet fouling?

Usually, wet fouling means your head gasket has blown, so the oil flows into the spark plug wells or cylinders. Another cause might be bad piston oil control rings or other problems with the valve train. It's not as likely, but this could be the symptom of your engine running super rich.


What does a yellowish brown buildup on your spark plugs mean?

This symptom is super uncommon, because leaded gasoline is really only used for racing these days. Lead fouling could cause misfires as you push the RPMs, like when you accelerate hard, which is a real problem when you're competing in motorsports. If you're not planning on racing, this won't apply to you.


Why would a spark plug melt?

Usually, when the center electrode is melted, it's from not tightening the spark plug in the threads all the way. You won't get as much power from your engine when this happens. Sometimes, this problem can be caused by hot spots in your engine, which usually means pre-ignition issues.


What does a white spark plug insulator with black spots mean?

Several issues can cause overheating, including ignition timing that's over-advanced, a lean air/fuel mixture, too low of a spark plug heat range, or a vacuum leak. Probably the most common problem is that the cooling system in your car isn't functioning properly, which is something you need to fix or plenty of other problems can pop up.


Do you ever need to gap modern spark plugs?

Because spark plug makers usually are using the same spark plug for all kinds of engines, they can't gap them all to the right setting. Sure, you might get lucky and the gap the plugs ship with works for your engine, but you really should check and set the gap with a gap tool, which takes like thirty seconds.


What does humidity do to electrode temperature?

If you live or are going to drive where the ambient humidity is high, you might need a higher voltage to ensure your engine runs correctly. That usually means upgrading the ignition coil, if the one you have isn't rated to put out more.


What drives a car's distributor?

In breaker-point ignitions, which are the oldest style out there in modern cars, the distributor runs as the crankshaft rotates. The great thing about this setup is figuring out problems and fixing them is easy.


Lower resistance between an ignition coil and the spark plugs results in what?

Lower resistance means the coil can make more power. Not only is more power always good, it makes the coil more reliable, since it can go longer without failing, which is also a really good thing. In racing, cars only have extremely low resistance coils.


Why do some cars have two spark plugs per cylinder?

Some modern engines use this unique design to ensure all the fuel in each cylinder combusts. It leads to better efficiency and power, plus reduces deposit buildup. A second spark plug creates a twin flame front, so there are no hot spots in the cylinders. These are all good things.


What is a variable pitch ignition wire?

The alternating tightly and loosely wound copper wires around the plug wire provides a definite advantage. It works to get rid of most radio frequency interference, which is created by the ignition system, resulting in optimal resistance and performance.


What does RFI stand for?

All electrical systems in a car create RFI, or electrical noise, including the ignition system. If you're using sensitive electronic equipment, RFI might interfere with your readings. Things like spark plug caps and resistor wires can help cut down on this factor, so you don't have to deal with the issues.


How often should you replace your spark plugs?

Every engine is different, so you really should rely on what your car's manufacturer says. Just look in the owner's manual for a spark plug change interval, or go to the automaker's website for that info. They'll know about how long spark plugs will realistically last.


When do you need special spark plugs?

As compression in your engine rises, so does the heat. The whole point of spark plugs is to get rid of the heat in the cylinders, so you'll have to switch to a colder heat range by getting new spark plugs, otherwise you could suffer some performance issues. This would be for big modifications, not small ones.


When should you use resistor spark plugs?

Because spark plugs and the ignition system can generate electrical noise that will mess with computers, you should use resistor style plugs if you have such a setup. The same is true if you have two-way radios, a GPS system, or other onboard electronics.


What is pre-ignition?

Anytime the spark plugs fire and ignite the air-fuel mixture in the cylinders too early, or before the ignition timing you or the vehicle manufacturer has set, this is called pre-ignition. It can cause all sorts of problems, including fouling the plugs, reducing power, and creating engine deposits.


How do you know when a spark plug is tightened correctly?

All spark plugs come with a specific torque rating. If you tighten a plug too much, it can break and you have a real mess on your hands. A loose spark plug can trigger overheating and other damage.


Can you get more power by upgrading spark plugs?

Many people think swapping the spark plugs in your engine will make more power. The only time they really help to improve horsepower is when your current spark plugs are worn out. You do need different spark plugs as you increase engine power, but the spark plugs don't make that extra power.


What is detonation?

Detonation is absolutely not good for your spark plugs, since it can break them. The cause of detonation is too much heat and pressure in the cylinder, which just makes the air and fuel ignite before it should.


A spark should happen before the piston gets to where?

Ideally, the spark happens right before the piston reaches the top of the compression stroke, resulting in the most power and best efficiency possible. Ignition anywhere else in the process will mean your engine doesn't run as well.


As engine RPMs climb, the spark needs to happen when?

Fuel always takes about the same amount of time to burn. To adjust for engine components moving faster, the spark plugs need to fire sooner. The term for this adjustment is spark advance, allowing for higher and higher RPMs in engines.


Spark retardation refers to what?

As you retard the spark on your engine, that means the plugs fire closer to the top of the compression ratio. Be careful, because too much retardation can move things back so far you suffer power loss.


What differentiates a hot and cold spark plug?

Whether you need a hot or cold spark plug really depends on your car. Hot plugs feature a smaller contact area on the tip, while cold plugs increase that contact area so they run at lower temperatures. See your car owner's manual to decide which you need.


How many wire coils are in an ignition coil?

Ignition coils are shockingly simple devices, no pun intended. Basically, they're a high-voltage transformer that features two wires, with one being the primary coil. The secondary coil is wrapped around it.


Distributors transfer voltage from what?

The distributor performs a variety of functions. It's most important task is to transfer voltage from the coil, sending it through the correct wire to each of the cylinders in the right timing order. A bad distributor can make your car run rough, or not at all.


What does the ceramic insert on a spark plug do?

You absolutely don't want spark to happen anywhere but the tip of the electrode, which is what the ceramic insert guarantees will happen. The insert performs another vital function, helping to burn off deposits that would otherwise build up and diminish the spark.


To help with timing, engine control units track what?

Modern cars have an onboard engine control unit or ECU that will always know where the pistons are. This enables it to time the spark at just the right time, so you get ignition at the peak of compression, and not before or after.


If you car doesn't have a distributor, what controls ignition timing?

It's the ECU's job to manage the ignition coil, through a series of transistors. This setup means you get precision control, which is why so many modern cars have switched over to this approach for an ignition system.


How quickly do distributors run compared to the crankshaft?

Gears on the bottom of the distributor and the crankshaft mesh together. They're purposely designed to spin the distributor at half the speed, since it doesn't need nearly as many revolutions to perform its job.


What's another term for a spark plug wire?

Some people will call the cables that connect the distributor cap to the spark plugs just wires. Other people think that's a confusing name, preferring to call them leads. You just should know both terms, even if you prefer to use one of them.


When does a battery help produce ignition?

When the engine is running, the distributor powers the ignition system, while the alternator takes care of everything else electrical. A bad battery will keep your car from starting because no electricity, or not enough, will reach the spark plugs.


What does the ignition switch control?

As you turn the key in your car, the ignition switch opens up a connection between the battery and the ignition system. Once you close that off by not twisting the key, the battery can start to recharge via a connection with the alternator, so it's ready to start the engine up later.


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