Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Identify and describe major EFI components (Sensors, Actuators, ECU).
• Explain the function of each EFI component.
• Describe the principles of different EFI systems.
• Use a scan tool to interpret Diagnostic Trouble Codes (DTCs).
• Perform basic diagnostic tests on EFI components.

Lesson summary

This week, we delve into vehicle systems and diagnostics, focusing on electronic fuel injection (EFI) systems and basic engine diagnostics. This knowledge is crucial for Mechanical Technology students in South Africa because the automotive industry is a significant employer and offers diverse career paths. Understanding EFI systems, which are prevalent in modern vehicles, is essential for diagnosing performance issues, ensuring fuel efficiency (especially vital with rising petrol prices), and minimizing harmful emissions, which impact our environment and public health.

Lesson notes

2.1 Electronic Fuel Injection (EFI) Systems What is EFI? Electronic Fuel Injection (EFI) is a system that precisely controls the amount of fuel injected into the engine, replacing carburetors which were less efficient and accurate. EFI systems use sensors, actuators, and an Engine Control Unit (ECU) to optimize fuel delivery for varying engine conditions. This leads to improved fuel economy, reduced emissions, and enhanced engine performance.

Major Components of an EFI System: Sensors: These devices monitor various engine parameters and send signals to the EC

U. Key sensors include: Mass Airflow (MAF)

Sensor: Measures the amount of air entering the engine. This is crucial for determining the correct air-fuel mixture.

Manifold Absolute Pressure (MAP)

Sensor: Measures the pressure in the intake manifold, providing an indication of engine load.

Throttle Position Sensor (TPS): Monitors the throttle valve position, indicating driver demand.

Engine Coolant Temperature (ECT)

Sensor: Measures the engine coolant temperature, influencing fuel enrichment during cold starts.

Oxygen (O2)

Sensor (Lambda Sensor): Located in the exhaust system, it measures the oxygen content in the exhaust gases, providing feedback to the ECU for fine-tuning the air-fuel mixture and controlling catalytic converter efficiency.

Crankshaft Position (CKP)

Sensor: Determines the position and speed of the crankshaft, crucial for ignition and fuel injection timing.

Camshaft Position (CMP)

Sensor: Identifies the position of the camshaft, used in sequential EFI systems.

Actuators: These devices are controlled by the ECU to adjust engine parameters.

Key actuators include: Fuel Injectors: Electrically controlled valves that spray fuel into the intake manifold or directly into the combustion chamber.

Idle Air Control (IAC)

Valve: Controls the amount of air bypassing the throttle valve during idle, maintaining a stable idle speed. Electronic Throttle Control (ETC)

System (Drive-by-Wire): Replaces the mechanical throttle linkage with electronic sensors and actuators to control throttle valve opening.

Engine Control Unit (ECU): The "brain" of the EFI system. It receives signals from the sensors, processes the information, and sends commands to the actuators to control fuel injection, ignition timing, and other engine functions.

Fuel Pump: Supplies fuel from the fuel tank to the fuel injectors under pressure.

Fuel Filter: Removes contaminants from the fuel to protect the fuel injectors.

Fuel Pressure Regulator: Maintains a constant fuel pressure at the fuel injectors.

Types of EFI Systems: Throttle Body Injection (TBI): A single or dual fuel injector(s) is/are located in the throttle body, spraying fuel into the intake manifold. Simpler and less expensive than multi-port injection.

Multi-Port Fuel Injection (MPFI): Each cylinder has its own fuel injector located near the intake valve. This provides more precise fuel delivery and better performance compared to TB

I. Batch-Fire Injection: Fuel injectors are fired in groups, rather than individually.

Sequential Fuel Injection: Fuel injectors are fired individually, timed to coincide with the intake stroke of each cylinder. This is the most advanced and efficient type of EFI system.

Direct Injection (GDI/DI): Fuel is injected directly into the combustion chamber, rather than into the intake manifold. This allows for higher compression ratios, improved fuel economy, and reduced emissions.

Principles of Operation: The ECU uses a pre-programmed map (lookup table) that correlates sensor inputs with optimal fuel injection and ignition timing settings. This map is constantly updated based on real-time sensor data. For example, if the engine is cold (ECT sensor reads low temperature), the ECU will enrich the fuel mixture to aid cold starting. If the engine is under heavy load (MAP sensor reads high pressure), the ECU will increase fuel delivery to provide more power. The O2 sensor provides feedback to the ECU, allowing it to fine-tune the air-fuel mixture to maintain optimal catalytic converter efficiency and minimize emissions. 2.2 Basic Engine Diagnostics Common Engine Problems and Symptoms: Rough Idle: Can be caused by vacuum leaks, faulty spark plugs, dirty fuel injectors, or a malfunctioning IAC valve.

Poor Fuel Economy: Can be caused by a faulty O2 sensor, a clogged air filter, or a malfunctioning fuel injector.

Loss of Power: Can be caused by a clogged fuel filter, a faulty fuel pump, or a malfunctioning ignition system.

Engine Misfires: Can be caused by faulty spark plugs, ignition coils, or fuel injectors.

Engine Knocking/Pinging: Can be caused by low octane fuel, excessive carbon buildup in the combustion chamber, or a faulty knock sensor.

Difficulty Starting: Can be caused by a weak battery, a faulty starter motor, or a malfunctioning fuel pump.

Excessive Smoke from Exhaust: Blue smoke indicates burning oil, black smoke indicates a rich fuel mixture, and white smoke indicates burning coolant.