ASVAB Study Guide

Comprehensive preparation for the Armed Services Vocational Aptitude Battery

Auto & Shop Information

Knowledge of automotive systems, shop tools, and maintenance procedures

Core Concepts

Introduction to Auto and Shop Information on the ASVAB

The Auto and Shop Information (AS) section of the ASVAB tests your knowledge of automobile technology and tools used for automotive maintenance and woodworking. This section evaluates your understanding of how cars work, basic repair procedures, and the proper use of various tools.

Test Format:
  • CAT-ASVAB (computerized version): 11 questions in 7 minutes
  • P&P-ASVAB (paper version): 25 questions in 11 minutes

Automotive Systems

Engine Fundamentals

Four-Stroke Cycle:

  1. Intake: Piston moves down, intake valve opens, air-fuel mixture enters cylinder
  2. Compression: Piston moves up, valves closed, mixture is compressed
  3. Power: Spark plug ignites mixture, expanding gases force piston down
  4. Exhaust: Piston moves up, exhaust valve opens, spent gases exit cylinder
Stroke Piston Movement Valve Position Action
Intake Downward (TDC to BDC) Intake: Open
Exhaust: Closed		 Air-fuel mixture enters cylinder
Compression Upward (BDC to TDC) Both closed Mixture is compressed
Power Downward (TDC to BDC) Both closed Spark ignites mixture, piston forced down
Exhaust Upward (BDC to TDC) Intake: Closed
Exhaust: Open		 Spent gases exit cylinder

Fuel System Components

Cooling System Components

Shop Tools and Safety

Hand Tools

Wrenches
  • Open-End: U-shaped opening
  • Box-End: Enclosed opening
  • Socket: Attached to ratcheting handle
  • Torque: Measures applied torque
Screwdrivers
  • Flathead: Single flat blade
  • Phillips: Cross-shaped tip
  • Torx: Star-shaped tip
  • Hex/Allen: Hexagonal tip
Pliers
  • Slip-Joint: Adjustable pivot
  • Needle-Nose: Long tapered jaws
  • Locking: Can be locked in position
  • Channel-Lock: Adjustable jaw width

Power Tools

Workshop Safety

Examples and Applications

Four-Stroke Engine Cycle

Scenario: A car engine is running at idle speed. What happens in one cylinder during a complete four-stroke cycle?

Explanation:

  1. Intake Stroke: Piston moves down, intake valve opens, air-fuel mixture enters
  2. Compression Stroke: Piston moves up, valves closed, mixture compressed
  3. Power Stroke: Spark plug fires, mixture ignites, piston forced down
  4. Exhaust Stroke: Piston moves up, exhaust valve opens, gases exit

Key Insight: The four-stroke cycle requires two complete revolutions of the crankshaft. Only the power stroke produces energy.

Brake System Operation

Scenario: A driver notices the brake pedal feels soft and must be pressed almost to the floor to stop effectively.

Explanation:

Normal brake operation relies on hydraulic pressure transmission. A soft pedal typically indicates air in the brake lines, which is compressible unlike brake fluid.

Solution: Bleed the brake system to remove air, which involves opening bleeder valves at each wheel while applying pressure to the system.

Cooling System Function

Scenario: A vehicle overheats in stop-and-go traffic on a hot day.

Explanation:

At low speeds, reduced airflow through radiator requires the cooling fan to compensate. Possible causes include malfunctioning fan, low coolant, blocked radiator, or failed water pump.

Immediate Actions: Turn on heater to draw heat from engine, pull over and shut off engine. Never remove radiator cap when hot.

Tire Wear Patterns

Scenario: Technician notices uneven tire wear during inspection.

Explanation:

  • Center Wear: Overinflation
  • Edge Wear: Underinflation
  • One-Sided Wear: Improper wheel alignment
  • Cupping: Worn suspension components

Key Insight: Tire wear patterns reveal problems beyond just tires, including suspension and alignment issues.

Using a Multimeter

Scenario: Diagnosing electrical problems in a vehicle's charging system.

Explanation:

  • Measuring Voltage: Set to DC Volts, red to positive, black to negative
  • Continuity Testing: Set to continuity, probes to both ends of wire
  • Current Draw: Set to DC Amps, connect in series with circuit

Key Insight: A multimeter is essential for electrical diagnostics. Always start with higher measurement ranges.

Review Section

Key Concepts Summary

Automotive Systems Overview

System Key Components Function
Engine Block, pistons, crankshaft, valves Converts fuel to mechanical energy
Fuel System Tank, pump, injectors, filter Delivers fuel to engine
Cooling System Radiator, water pump, thermostat Regulates engine temperature
Brake System Master cylinder, calipers, pads, rotors Slows and stops vehicle
Electrical System Battery, alternator, starter Provides electrical power

Common Pitfalls and Misconceptions

Engine Misconceptions
  • Myth: Premium fuel makes any car run better
  • Reality: Only beneficial in engines designed for it
  • Why it matters: Wasting money on unnecessary premium fuel
Brake System Errors
  • Error: Uneven pad replacement
  • Solution: Always replace pads in axle pairs
  • Prevention: Follow manufacturer service procedures
Tool Usage Mistakes
  • Error: Using pliers instead of wrenches
  • Result: Rounded bolt heads
  • Solution: Use proper wrench that fits fastener exactly

Memory Aids and Tricks

Four-Stroke Engine Cycle: "SUCK, SQUEEZE, BANG, BLOW"

  • SUCK: Intake stroke
  • SQUEEZE: Compression stroke
  • BANG: Power stroke
  • BLOW: Exhaust stroke

Diagnosing Engine Problems: "FAST"

  • F: Fuel (Is fuel reaching engine?)
  • A: Air (Is air flowing properly?)
  • S: Spark (Is ignition creating spark?)
  • T: Timing (Correct valve/ignition timing?)

Tire Wear Patterns: "CUE"

  • Center wear = Overinflation
  • Edge wear = Underinflation
  • One-sided wear = Alignment issues

Quick Review Questions

1. What are the four strokes of a four-stroke engine?

Intake, compression, power, exhaust

2. What causes a soft brake pedal?

Air in brake lines or failing master cylinder

3. What is the purpose of a catalytic converter?

To reduce harmful emissions

4. What tool measures electrical voltage?

Multimeter set to volts

5. What causes center wear on tires?

Overinflation

6. What is the function of an alternator?

Generate electricity to power systems and charge battery

Final Tips for the Auto and Shop Information Section

  1. Focus on fundamentals: Understand how basic automotive systems work
  2. Learn tool identification: Be able to identify common tools and their uses
  3. Know safety procedures: Understand basic shop safety practices
  4. Understand diagnostics: Learn logical approaches to common problems
  5. Familiarize with terminology: Know correct names for parts and tools
  6. Visualize systems: Picture how components work together
  7. Use process of elimination: Eliminate obviously wrong answers

Practice Test

Question 1

Which engine stroke produces power to drive the vehicle?

Intake stroke
Compression stroke
Power stroke
Exhaust stroke

The four-stroke cycle consists of intake, compression, power, and exhaust strokes. Only the power stroke produces energy to drive the vehicle, when the compressed air-fuel mixture is ignited and expands, forcing the piston down.

Question 2

What component in the cooling system regulates the flow of coolant based on temperature?

Water pump
Thermostat
Radiator
Heater core

The thermostat opens and closes based on coolant temperature, regulating the flow of coolant between the engine and radiator. When the engine is cold, the thermostat remains closed to allow the engine to warm up quickly.

Question 3

What is the purpose of a catalytic converter?

To reduce engine noise
To reduce harmful emissions
To increase engine power
To improve fuel economy

The catalytic converter contains precious metals that act as catalysts to convert harmful pollutants in exhaust gases into less harmful substances.

Question 4

Which of the following is NOT a component of a disc brake system?

Caliper
Rotor
Brake shoe
Brake pad

Brake shoes are components of drum brake systems, not disc brake systems. A disc brake system consists of a caliper, rotor (disc), brake pads, and hydraulic components.

Question 5

What is the function of the alternator in a vehicle?

To start the engine
To generate electricity while the engine is running
To store electrical energy
To regulate fuel flow to the engine

The alternator is driven by the engine via a belt and generates electricity to power the vehicle's electrical systems and recharge the battery while the engine is running.

Test Results

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Review the explanations for each question to understand the correct answers.