ASVAB AUTO AND SHOP INFORMATION PART 1

What is an internal combustion engine?

An internal combustion engine (ICE) is an engine that burns fuel inside the engine's cylinders to create energy.

What does the burning create in an internal combustion engine?

The burning creates high-pressure gases that push the piston and produce motion.

What is combustion?

Combustion is the burning of fuel with oxygen.

What happens when fuel is burned?

• Heat is released.

• High-pressure gases are produced.

• These gases push the piston and create mechanical work.

Fuel + Oxygen + Ignition = Combustion

How does a gasoline (Spark Ignition or SI) engine work?

• Air and gasoline enter the cylinder.

• The piston compresses the mixture.

• The spark plug creates a spark.

• The spark ignites the fuel-air mixture.

• The explosion pushes the piston downward.

• The piston turns the crankshaft, producing mechanical energy.

Gas = Spark

What is Spark Ignition (SI)?

Spark Ignition (SI) means the engine uses a spark plug to ignite the compressed mixture of gasoline and air.

What is a Spark Ignition used in?

• Gasoline cars

• Most passenger vehicles

How does a diesel (Compression Ignition or CI) engine work?

• Only air enters the cylinder.

• The piston compresses the air extremely tightly.

• Compression makes the air very hot.

• Diesel fuel is injected.

• The hot air ignites the diesel automatically.

• The explosion pushes the piston downward.

Diesel = Heat from Compression

What does Diesel engines not use?

Spark Plugs

What is Compression Ignition (CI)?

Diesel fuel ignites because the air becomes extremely hot from being compressed.

Is a spark plug needed for Compression Ignition?

No

What does Gasoline use that Diesel doesnt?

Gasoline needs spark to ignite fuel

What does Gasoline use that Diesel doesnt?

What does Diesel use to ignite fuel?

Heat from compression

What does Diesel use to ignite fuel?

What ignition does Gasoline use?

Spark Ignition

What ignition does Diesel use?

Compression Iginition

How does an internal combustion engine produce work?

Burning fuel creates hot, expanding gases that push the piston downward.

The piston turns the crankshaft, changing the up-and-down motion into rotating motion that powers the vehicle.

What are the steps for an internal combustion engine?

Fuel → Burn → Expanding Gas → Piston Moves → Crankshaft Turns → Vehicle Moves

What powers a car's electrical system?

• Battery → Provides electricity to start the car.

• Alternator → Produces electricity and recharges the battery while the engine is running

What happens when you turn the key or push the Start button?

• An electrical circuit is completed.

• The battery sends electricity to the starter motor.

• The starter motor turns the crankshaft.

• The crankshaft starts the engine.

Steps that occur when you turn the key or push the Start button?

Key → Battery → Starter Motor → Crankshaft → Engine Starts

What is the job of the car battery?

• Stores electrical energy.

• Supplies electricity to start the engine.

• Powers electrical components before the engine starts.

Does the battery power the car continuously while driving?

No, the battery does not.

What is the purpose of the starter motor?

• Receives electricity from the battery.

• Turns the crankshaft.

• Starts the engine.

Can the engine begin running if there is no stater moter?

No, this is because the stater motor spins the engine

What does the crankshaft do?

• Is turned by the starter motor.

• Converts the pistons' up-and-down motion into rotating motion.

• Keeps the engine running once combustion begins.

Crankshaft = Converts piston movement into rotation.

What does the crankshaft do?

What is the purpose of the alternator?

• The engine turns a pulley.

• The pulley spins the alternator.

• The alternator generates electricity.

• It recharges the battery.

• It powers most of the vehicle's electrical systems (lights, radio, dashboard, etc.).

What is the purpose of the alternator?

What provides most of the electricity while driving?

The alternator

Alternator = Makes Electricity While You Drive

How does the alternator work?

The running engine turns a belt and pulley system, which spins the alternator.

The spinning alternator converts mechanical energy into electrical energy.

What are the steps for the alternator to work?

Engine → Pulley/Belt → Alternator → Electricity

What is the function of the starter solenoid?

The solenoid is a heavy-duty electrical relay.

What is the job of the stater solenoid?

• Connect the battery to the starter motor.

• Allow a large amount of current to reach the starter motor only when starting the car.

Solenoid = Electrical Switch for the Starter

What is the Battery?

• Stores electricity

• Starts the car

What is the Stater Motor?

• Uses battery power

• Turns the crankshaft

• Starts the engine

What is the Alternator?

• Runs after the engine starts

• Produces electricity

• Recharges the battery

What is the correct order for starting a car?

• Turn the key or press Start.

• Electrical circuit is completed.

• Battery sends electricity.

• Solenoid activates.

• Starter motor turns the crankshaft.

• Engine starts.

• Engine spins the pulley.

• Pulley turns the alternator.

• Alternator powers the car and recharges the battery.

Key → Battery → Solenoid → Starter → Crankshaft → Engine → Pulley → Alternator → Battery Recharge

What spins the alternator?

Pully/Belt

What are the most common electrical reasons a car won't start?

• Battery (dead or discharged)

• Starter

• Alternator

How can a bad alternator prevent a car from starting?

A bad alternator doesn't recharge the battery while the engine is running.

Alternator = Charges the Battery While Driving

What happens as the battery loses charge?

• Dim headlights (especially at low engine speeds)

• Weak electrical accessories

• Eventually, the battery dies and the car won't start.

How can you tell whether the problem is the starter, battery, or alternator?

🚗 If it won't jump-start

➡ Suspect the starter.

How can you tell whether the problem is the starter, battery, or alternator?

🚗 If it jump-starts but won't stay running

➡ Suspect the battery.

How can you tell whether the problem is the starter, battery, or alternator?

🚗 If it starts and stays running after a jump

➡ Suspect the alternator (it may not be charging the battery).

What can you also check if there is a problem regarding the starter, battery, or alternator?

A light may have been left on, draining the battery.

What does a clogged fuel filter cause?

A clogged fuel filter blocks fuel from reaching the engine.

Filter = Fuel Flow.

What are the signs for a clogged fuel filter?

• 🚫 Car may not start

• 🚗 Engine may sputter or hesitate, especially at high speeds

What is a fuel pump?

The fuel pump moves gasoline from the fuel tank to the engine.

What are the causes of a fuel pump failure?

• Electrical problems

• Normal wear and tear

• Contamination (dirty fuel)

• Overheating

Pump = Pushes fuel.
No pump → No fuel → No start.

What does a clogged fuel injector cause?

Fuel injectors spray fuel into the engine.

What happens if the fuel injector is dirty or clogged?

• ⛽ Poor fuel economy (uses more gas)

• 🌫 Increased emissions

• 🚗 Rough idling (engine shakes while stopped)

• 📉 Poor engine performance or sluggish acceleration

If it's clogged, the engine can't "spray" fuel correctly.

What are the symptoms of clogged fuel filters?

Won't start or sputters at high speed

Filter → Flow problem 🚫⛽

What are the symptoms of faulty fuel pumps?

Won't start because fuel isn't reaching engine

Pump → Push problem 🔋⛽

What are the symptoms of clogged fuel injectors?

Rough idle, poor performance, bad gas mileage, higher emissions

Injector → Spray problem 💦⛽

What is spark plug fouling?

Spark plug fouling happens when carbon deposits build up on the spark plug tip, preventing it from creating a strong spark.

Carbon covers the spark = weak spark.

What problems does spark plug fouling cause?

• ❌ Engine misfires

• ❌ Rough running

• ❌ Hard starting

• ❌ Increased carbon emissions

Dirty plug = Dirty engine performance.

Why does spark plug fouling happen?

It usually happens because the engine doesn't get hot enough to burn off extra fuel and carbon.

What are the most common causes of a spark plug fouling?

• Long periods of idling

• City driving with frequent stops

• Short trips

Cold engine = Carbon buildup.

How can spark plug fouling be prevented?

Drive at highway speeds occasionally.

How does a hot engine clean spark plugs?

• The engine reaches a higher temperature

• Extra heat burns off carbon, fuel, and ash from the spark plugs

What is the valvetrain?

Controls when the engine's valves open and close so the engine runs correctly.

What does the valvetrain do?

• ✅ Air-fuel mixture enters at the right time.

• ✅ Exhaust gases leave at the right time.

What is the camshaft?

A rotating shaft with cams (lobes) that push on the valves.

What is the job of the camshaft?

• Open intake valves

• Open exhaust valves

• Control valve timing

It is surrounded by engine oil to reduce wear.

What do the intake valves do?

Let the air-fuel mixture enter the combustion chamber before ignition.

Intake valves let the mixture IN.

What do the exhaust valves do?

Let the burned gases leave the combustion chamber after combustion.

The gases then travel to the exhaust manifold.

Exhaust valves let gases OUT.

What do the exhaust valves do?

What is the crankcase?

The crankcase is the lower part of the engine.

What does the crankcase do?

• Holds the engine oil

• Houses the crankshaft

• Houses the connecting rods

Crankcase holds the crankshaft and oil.

What is the crankshaft?

The crankshaft converts the pistons' up-and-down motion into rotating motion.

What does the crankshaft do?

• Drives the camshaft

• Uses a timing belt, timing chain, or gears

Crankshaft spins the engine.

What are the common types of drivetrain configurations?

• Rear wheel drive

• Front wheel drive

• All wheel drive

• Four-wheel drive

Rear Wheel Drive

Rear-wheel drive sends engine power to the rear wheels through the driveshaft.

RWD = Rear wheels are powered.

What is Front-Wheel Drive (FWD)?

Front-wheel drive sends engine power to the front wheels using a transaxle, which combines the:

• Transmission

• Front axle

• Differential

Since the engine is over the front wheels, it provides better traction, especially on slippery roads.

What is All-Wheel Drive (AWD)?

All-wheel drive sends power to both the front and rear wheels using a transfer case, which automatically distributes engine power (torque) between both axles.

AWD = All wheels receive power automatically.

What is Four-Wheel Drive (4WD)?

four-wheel drive uses a special transfer case to send power to all four wheels when extra traction is needed, such as:

• Off-road

• Mud

• Snow

• Rocks

The driver can often switch between 2WD and 4WD depending on road conditions.

4WD = Driver chooses four-wheel power for tough terrain.

What are the symptoms of a broken or faulty timing belt?

• 🔊 Engine ticking noise

• 🚗 Rough idle

• ⚡ Engine misfires

• 🛢 Low oil pressure

• 🌫 Smoke from the engine

What serious engine damage can a broken timing belt cause?

• Bent or broken valves

• Damaged or broken pistons

This happens because the camshaft and crankshaft are no longer synchronized, allowing the pistons and valves to collide.

Why does a bad timing belt cause engine problems?

The timing belt keeps the crankshaft and camshaft moving together so the valves open and close at the correct time.

If it fails:

• Valve timing is incorrect.

• The engine runs poorly or may not run at all.

Why does a failing piston ring cause engine smoke?

Normally, piston rings keep oil out of the combustion chamber.

What happens to a failing piston ring when it wears out?

• Oil leaks into the chamber.

• The oil burns during combustion.

• Smoke comes out of the exhaust.

Oil in the combustion chamber = Smoke out the exhaust.

What happens when piston rings fail?

When piston rings fail, engine oil leaks into the combustion chamber.

This causes:

• 🌫 Blue/gray engine smoke

• Increased oil consumption

Bad piston rings = Oil burns with the fuel.

What are the symptoms of a bad camshaft?

• Rough idling

• Frequent stalling

• Poor fuel economy

• Slow acceleration

• Difficulty starting

Bad camshaft = Engine runs rough and loses power.

What are the symptoms of a bad crankshaft?

• 🚗 Difficulty starting the vehicle

• ⚠ Intermittent stalling (engine randomly shuts off)

Bad crankshaft = Hard to crank (start).

What is the path of the exhaust system?

The exhaust leaves the combustion chamber through the exhaust valve, is collected by the exhaust manifold, cleaned by the catalytic converter, quieted by the muffler, and exits through the tailpipe.

Chamber → Valve → Manifold → Converter → Muffler → Tailpipe

What does the exhaust valve do?

The exhaust valve opens after combustion and allows the burned gases to leave the combustion chamber.

Exhaust valve = Opens so gases can EXIT.

What does the exhaust manifold do?

• Collects exhaust gases from all cylinders

• Directs the gases into the exhaust pipe

• Helps reduce engine noise

Manifold = Collects exhaust from every cylinder.

What does the catalytic converter do?

• Filters harmful pollutants

• Converts them into less harmful gases, mainly:

  • Water vapor (H₂O)

  • Carbon dioxide (CO₂)

Catalytic converter = Cleans the exhaust.

What does the muffler do?

The muffler reduces the noise made by the engine before the exhaust leaves the vehicle.

Muffler = Makes the car quieter.

What does the tailpipe do?

The tailpipe is the final part of the exhaust system.

It releases the cleaned exhaust gases away from the vehicle.

Tailpipe = Final exit for exhaust gases.

What is the drivetrain?

The drivetrain transfers power from the engine to the wheels so the vehicle can move.

What do the crankshaft do?

Turns piston movement into rotation

What do the flywheel do?

Keeps engine rotation smooth and steady

What does the clutch do?

It connects and disconnects the engine from the transmission.

• Lets you shift gears

• Stops engine power from reaching wheels without turning off engine

What does the transmission do?

It changes gear ratios to control speed and torque.

• Increases torque for starting/moving

• Adjusts speed for driving conditions

What does the differential do?

It splits power to the wheels so they can rotate at different speeds.

• Important when turning

• Outside wheel spins faster than inside wheel

Besides steering system problems, what else can cause steering issues?

Wheel alignment problems (part of the suspension system).

• Misalignment affects how the car tracks straight

• Causes pulling, drifting, or uneven steering

• Proper alignment keeps the vehicle driving straight when the steering wheel is briefly released

BRAKE SYSTEM

What starts the braking process?

Pressing the brake pedal starts the system.

BRAKE SYSTEM

What does the master cylinder do in braking?

It pushes brake fluid into the brake lines.

BRAKE SYSTEM

What do brake lines do?

They carry brake fluid pressure to each wheel.

BRAKE SYSTEM

What activates the calipers to stop the wheels?

Brake fluid activates the calipers at each wheel.

BRAKE SYSTEM

How do the wheels actually stop?

Calipers create friction on the wheels, which slows and stops them.

What are the two main types of brakes on cars?

• Disc brakes (most common; usually front wheels)

• Drum brakes (sometimes used on rear wheels)