Now we need to take some time to work out how the internal combustion engine actually works. You will need to familiarize yourself not only with the parts of the engine, but also the functions they confer within the overall system at play. We begin with fuel, which is pumped into the engine courtesy of a fuel pump. These engines typically contain many cylinders – and each cylinder contains a piston that moves up and down. Depending on the vehicle in question, the engine could have as little as four or as much as eight cylinders. The fuel – previously transferred into the engine by the fuel pump – is injected into these cylinders by the carburetor. You can think of the carburetor as a fuel injector!

Surrounding the internal combustion engine we find the cooling water jacket, containing numerous inlet and outlet valves to control the temperature of the engine itself. These valves are themselves connected to a radiator. It’s also worth noting the relevance of oxygen in this regard. In order for fuel to successfully combust, it needs to be in the presence of oxygen. This oxygen is made available via inlet valves within the engine – a critical component in the burning of fuel and, ultimately, the operation of the spark plug that drives down the piston in each cylinder. Problems relating to the internal combustion engine tend to revolve around these critical points – where the engine fails to maximize its use of a factor that fails to generate the rotational energy harvested by the crankshaft.

Possessing fundamental knowledge of the internal combustion engine is crucial to the success of your ASVAB Automotive and Shop Information exam – as it lies at the heart of almost every automobile. Connected to the ICE are, of course, numerous systems that rely on the successful operation of this engine. Let’s take a closer look at six of these systems and the individual functions and advantages they offer to a given vehicle.

In this section, we will take a look at six distinct systems integrally linked to the internal combustion engine, these include: the exhaust system, the cooling system, the transmission system, the suspension system, the braking system, and finally, the electrical system.

The Exhaust System

The exhaust system consists of a series of pipes all connected to the engine. These pipes are responsible for passing exhaust, or waste, gases from the engine through to an area of the automobile known as the muffler. This acoustical chamber is responsible for reducing the transmission of noise from the engine, as well as eliminating some of the pollutants created by the burning of fuel inside the engine. The exhaust system, in this sense, plays an important role in the reduction of noise and pollution. By dispersing these waste gases, it avoids a consequent build-up of pressure inside the engine in the first place – allowing the ICE to perform smoothly in its role as it burns up more and more fuel to feed the various systems.

The Cooling System

We noted above that the internal combustion engine needs to be kept at a constant temperature. The pressure and gases present in the engine would otherwise serve as a health hazard. This, as we saw, is achieved by the presence of a cooling jacket surrounding the ICE. Heat is also generated in the internal combustion engine through the vast amount of rapid movements taking place each and every moment – with each movement contributing to additional friction. This friction creates heat in the same way rubbing your hands together creates heat. The cooling system of automobiles dissipates this excess heat through the presence of coolant.

Coolant is a liquid pumped through pipes from the cooling system to bypass the ICE. As the coolant passes the ICE, it picks up excess heat and brings it back to the radiator – air flowing across the radiator will, in turn, cool the coolant down, and so the cycle continues. Cars are more likely to overheat on a blisteringly hot day as the air passing by the radiator is simply not cool enough to have an appreciable effect on the coolant.

The Transmission System

How do we transfer power from the engine to the wheels? The answer is – through the transmission system. As the power from the engine rotates what are known as transmission shafts (in conjunction with gears and joints), the automobile will begin to move. So, in essence, the transmission system is that part of the automobile that transfers power from the engine to the movement of the vehicle – this is achieved by passing the power through intermediaries such as gears, shafts, and joints. The transmission is of itself a gear system that spins. As this transmission spins faster, the speed will need to be controlled or else you could never drive the car.

This explains why several gears are used to regulate speed – with shifting gears up and down a sign of increasing and decreasing speed accordingly. Automobiles contain, of course, a clutch, and upon pressing this clutch it will disengage the transmission system for you to select another gear. After selecting this gear, you take your foot off the clutch to reengage the transmission with the new gear. Vehicles may have, instead, an automatic transmission, where this “clutch work” is performed for you. The transmission system is, therefore, an important regulatory system for the driver of the vehicle with the transfer of power from the engine to its fundamental framework.

The Suspension System

The system of a vehicle that attaches the wheels to the body of said vehicle is known as the suspension system. The wheels, however, are not connected directly to the body of the vehicle as this would result in potential damage while going over bumps and ramps. So, there needs to be in place some form of shock absorber that absorbs the shock while going over ramps and bumps. This maintains the overall integrity of the connections between the wheels and the body of the vehicle. There are two types of suspension that allow for this shock absorption effect: springs and dampeners.

Think of a regular spring – as you press down on it, it has the ability to withstand great pressures. This is the same phenomenon with the structure of cars, where a spring system connects the joints between the wheels and the body of the vehicle. The dampeners are, in essence, shock absorbers. They take the form of oil-filled cylinders, with one end connected the axle of each wheel, and the other end connected to the body of the vehicle itself.

The Braking System

As you press the brake pedal in the vehicle, you will activate the brakes of the automobile. When you press the brake pedal you, in effect, compress the piston to such an extent that hydraulic fluid oozes out and through what’s called the brake line piping. This fluid passes through a set of mechanical calipers, which squeeze the brake pads against the rotor of the car. The amount of friction produced by this motion slows the rotation of the wheels. As the brake pedal is released, springs are employed to return the calipers to the original position. The braking system is, therefore, a simple and effective system incorporated into the vehicle to slow the automobile down.

The Electrical System

This battery needs, of course, some method of recharging. This is achieved through the presence of an alternator. The alternator is that part of the electrical system that charges the battery. The alternator produces energy by rotating in order to generate electrical energy, and this electrical energy is used to charge the battery.

This system is probably the most complex of all the systems studied thus far. One of the main purposes of the electrical system is to provide the energy required to initiate the spark plug which, if you remember, is responsible for the regular movement of the piston within the cylinder. Electricity is, it must be said, a core component for the successful operation of the engine. The electrical system has a plethora of additional functions – such as powering lights, windows, and locks. The energy from the electrical system lies in the battery – with the wiring around the car revolving and relying upon its energy. These wires transfer the electrical energy, for example, from the battery directly to the spark plug.

As well as these main systems, we also have numerous gauges operating within the vehicle. These gauges monitor certain conditions, such as temperature, pressure, and level of fuel. Gauges are, as well as this, marked with the individual units they are measuring. Let’s take a brief look at some of the most common gauge types:

You may be shown a gauge in your exam and it’s very important you read the units correctly. Take a look at the following table which further details the information you need to know when correctly interpreting tables:

These gauges will be marked highlighting low levels as well as excessive levels. You should be able to determine this amount by reading the gauge in question. When answering questions on this, note the units of the gauge – take flow meter for example – where it could be measured in either cfm or gpm. Try not to assume they will use the same units in all questions, as the questions are designed to ensure you understand how to interpret the gauges in the first place. The flow meter is an important example, as it measures the degree to which liquids are propelled through the piping system of automobiles, and it’s to this topic that we now turn our attention.

Pumps are composed of numerous parts – base, impeller, case, shaft, bearings, and seals – but in order to work effectively it needs to have an energy source. This energy source could come from the battery, the internal combustion engine, or some other such means. Whatever the energy source, the pump now has the ability to pump liquid through the piping system as a consistent rate. The rate at which the liquid, or gas, is pumped through the piping can be measured in two different ways: as gallons per minute (gpm) or as cubic feet per minute (cpm). Pumps play a fundamental role in the operation of a vehicle, as they act to transfer liquids and gases from one place to another. Examples of different pumps include centrifugal pumps, metering pumps, diaphragm pumps, and positive displacement pumps.

As well as these gauges and pumps, you will also be expected to become familiar with the range of tools used when repairing common problems. You will be expected to identify the main types of tool and the different variety that exists between those tools. For instance, you should be aware a Stillson Wrench is also known as a Pipe Wrench – and that they are used to turn soft iron pipes. You should already be familiar with many of these tool types and, if not, you should take the time to operate each of these at some stage, as it will help cement its specific function in your mind.

In this section we looked at the nuts and bolts of the automotive. By analyzing the gauges, pumps, and tools, we get to grips with the inns and outs of what makes up an automobile as well as how we can monitor its behavior. You need to be able to read such gauges appropriately, while understanding the value of pumps throughout the entire system. Couple this with the tools required to fix problems as they arise, as you will have some appreciation of the importance of this section to your ASVAB Automotive and Shop Information exam. Before we take a look at the shop information component of your exam, we will first look at common maintenance problems with vehicles and, with the aforementioned knowledge; you should be able to think through what may have caused the problem and what steps you can take to rectify such a problem.

The complexity of modern day automobiles makes it impossible to define precise protocols for each individual model. However, what we can do is say what each model has in common, thereby facilitating a mechanism by which you can learn about how to repair vehicles. Over the course of your military career, you will invariably need to repair some complex individual type of vehicle, and you will be provided with a detailed manual highlighting the particulars of that model. At this stage, for your ASVAB Automotive and Shop Information exam, you only need to be able to recognize how to repair common automobile problems. In this section, we will go through such problems and highlighting the steps you can take to repair each example.

All vehicles require regular maintenance to operate effectively in the long run. This insures a long reliable lifetime of the vehicle in question, which also saves you extra costs. Some parts of the automobile will eventually wear out and wear away and this evidently need to be replaced. In addition, many internal vehicular parts will require regular lubrication, as their function depends on moving in a defined way. One of the chief examples of this is tires, which tend to wear away approximately between 35,000-75,000 miles. The tires themselves contain bars letting you know when they need to be replaced, though you should be aware front tires will wear quicker than rear tires due to the effects of rotation.

With this in mind, you are advised to switch the front and rear tires every 3,000-5,000 miles. Worn tires are a hazard and render your timing questionable in difficult environments involving snow, ice, and rain. Also, try to check the pressure of your tires regularly – as this prevents abnormal wear of your tires. With the tires now secure, you can focus on the lubrication problems of the internal wear of your vehicle. Both the engine and transmission require regular lubrication, to such a point that it sufficiently reduces friction between the moving devices in your engine. Many engine manufacturers positively recommend lubricating these critical points every three months, or 3,000 miles of completed journey.

Over time, some parts of your vehicle will need to be replaced. Devices such as the battery, spark plug, shock absorbers, and belts, all require close inspection to ensure they’re operating as per specification. If not, it may be time to replace them. Given your vehicle is also dependent upon fluids; these too will need to be checked. Fluids found in the cooling system, brakes, and transmission may require replacement at some point in the future. The time of this replacement will depend on the particular model you’re dealing with. For your ASVAB Automotive and Shop Information exam, you should be aware of the necessary checks involved in the repair of the vehicle, as many military disciplines necessitate this familiarity as you may be required to undertake such work in the future.

You will not be expected to have a detailed understanding of repairing every aspect of a vehicle – this is the job of the mechanic. However, as prospective military personnel, you should be able to diagnose simple problems, ones you might even have the knowledge to repair yourself. If the engine doesn’t start, for example, you can assume it’s related to fire, fuel, or oxygen. This is because all three of these factors need to be present in order for the engine to operate as it should. If one of these factors is missing, the engine will not start. Fire is provided by the spark of the spark plug, thus something may be wrong with the electrical system – you could investigate the operation of the battery or alternator or, alternatively, check the wires connecting these devices to check everything is of sound condition.

If the spark is not the problem, it may be due to fuel. Fuel is pumped from the fuel tank by the fuel wire to the engine. A damaged fuel pump, or a damaged fuel line, may be the cause of the problem. In addition, you could look at the carburetor (fuel injector) that regulates the quantity of fuel reaching the engine. If the fuel isn’t the problem, and the spark is operating well, you might want to look into the last factor: oxygen. Oxygen is needed for the ignition of the spark. Oxygen enters into the car via the air filter, which is itself controlled by many diverse valves. If the air filter is blocked or damaged, this would hamper the availability of oxygen to the engine – you just need to check the filter to see if it’s dirty.

This is pretty much all you’re expected to know in terms of maintenance and repair. The purpose of this section is to check whether you understand how the vehicle operates. Just like the human body, if you know what each part does you can work out where the problem is arising. In this sense, you should be able to identify the critical components of a car, what their individual function is, as well as being able to tell which part is responsible for something going wrong. If you’re unfamiliar with vehicles, this may come as a difficulty at first but, with time, it comes that much easier. This now concludes the automotive component of our ASVAB Automotive and Shop Information study guide – we will now advance onto the final section of our study guide – that concerning shop tools and materials.