The fuel system of a car is an important part of the engine system, ensuring that fuel moves from the tank to the engine and is burned efficiently. The efficiency of the fuel system directly affects the vehicle's performance, fuel economy and environmental impact. Depending on the type of engine - whether a gasoline engine or a diesel engine - the operating principles and advantages of fuel systems are different.

Functions and components of a car's fuel system

Main features:

1. Fuel transport: The fuel pump delivers fuel from the tank to the engine.
2. Fuel cleaning: The fuel filter removes dirt and impurities that can damage the system.
3. Fuel metering: The system ensures that the correct amount of fuel is delivered according to the engine load and speed.
4. Fuel preparation for combustion: The fuel that reaches the engine is mixed with air to achieve optimal combustion.

Construction and main components of the car fuel system:

• Fuel tank: A container for storing fuel, where the fuel is protected from leakage and evaporation.
• Fuel pump also known as High pressure pump or high pressure fuel pump or injection pump (external high pressure pump): Transports fuel to the engine, maintaining a stable pressure.
• Fuel feed pump (in-tank low pressure electric pump)
• Fuel filter: Removes contaminants, water and particles from the fuel.
• Injectors: Spray the fuel into the engine as a fine aerosol so that it mixes with the air effectively.
• Fuel pressure regulator: Ensures the correct pressure and fuel flow in the system.
• Electronic control unit (ECU-Engine Control Unit). Controls the amount of fuel and timing according to the needs of the engine. The ECU is the main control unit of the engine, responsible for controlling and coordinating several engine systems, including the fuel system, air intake, ignition (in gasoline engines), and exhaust. It is a central computer that uses data from sensors to control actuators and optimize engine performance. The function of the ECU is to control the fuel system. In petrol engines: controls the fuel injectors and ignition timing. In diesel engines: manages the EDC system.
• The EDC (Electronic Diesel Control) control unit is a special control system designed specifically for controlling diesel engines. It focuses mainly on the fuel injection process and other aspects of diesel engine performance.
• Engine speed sensors
• Fuel temperature sensor
• Fuel pressure sensor
• Fuel pressure control valve
• Shut-off valve or solenoid (fuel shut-off).The fuel system shut-off valve is a component commonly found in diesel engines that helps control the flow of fuel to the engine, allowing or stopping fuel delivery. It plays a key role in safely and efficiently shutting down the engine when necessary. The shut-off valve is often part of the fuel injection pump system and works in conjunction with other control mechanisms.
• Fuel Delivery Module (FDM) / Fuel Pump Module
• Fuel Pressure Regulator

 

 Engine speed sensors

Engine speed sensors (also known as crankshaft or camshaft sensors) play an important role in the fuel system, as they provide precise information about the engine's speed and position. This information is used by the engine control unit (ECU) to precisely control the fuel system and ignition system, ensuring optimal engine performance and efficiency.

Functions of engine speed sensors in the fuel system

1. Fuel injection timing:

   • Engine speed sensors provide the ECU with information about the position of the crankshaft and camshaft, allowing the control unit to calculate the exact timing of when fuel should be injected.
   • This is particularly important in both diesel engines (where fuel is injected under high pressure at the right moment) and gasoline engines (where injection and ignition must be synchronized).

2. Ignition system timing:

   • In gasoline engines, RPM sensors determine when the spark plugs should ignite the fuel-air mixture. Precise timing increases engine efficiency and reduces fuel consumption.

3. Monitoring engine speed:

   • The ECU monitors engine speed to optimize the fuel system. For example, the control unit adjusts the speed at idle, when accelerating, or when working under load.
   • The signals from the speed sensors help maintain stable engine operation under various conditions.

   Idle control:

   • Using the RPM sensors, the ECU can adjust the fuel quantity and airflow to keep the engine stable at idle.

   Protection and fault detection:

   • If the engine speed sensor sends incorrect or incomplete signals, the ECU may stop fuel injection to prevent engine damage.
   • Faults in engine speed sensors can lead to increased fuel consumption, decreased engine performance, or even engine failure.

4. Turbo and high-pressure pump control:

   • In diesel engines, the operation of the turbo and high-pressure pumps is controlled based on speed data, ensuring that fuel is pumped according to the engine's needs.

Types of engine speed sensors

1. Crankshaft sensor:

   • Monitors crankshaft rotation and position.
   • Important for timing fuel injection and ignition systems.

   Camshaft sensor:

   • Monitors the rotation of the camshaft, which controls the opening and closing of the valves.
   • Together with the crankshaft sensor, it ensures synchronized fuel injection and valve operation.

Engine speed sensor failure and its effects

• Incorrect fuel injection: An incorrect or incomplete signal causes timing problems that reduce engine performance.
• Idling problems: The engine may run unevenly or stall.
• Increased fuel consumption: An incorrect signal causes inefficient fuel combustion.
• Engine stalling: A complete sensor failure prevents the engine from starting or can cause it to stall unexpectedly.

Summary

Engine speed sensors are essential to the fuel system and overall engine operation. They enable precise fuel injection and ignition timing, helping to ensure engine performance, efficiency and fuel economy are optimized. Failure of these sensors can cause serious problems with engine reliability, which is why it is important to ensure that they are regularly checked and replaced if necessary.

Fuel Temperature Sensor

The Fuel Temperature Sensor, FTS, is a component that measures the temperature of the fuel before it enters the engine's fuel system. This information is used by the Engine Control Unit (ECU) to precisely adjust engine operating parameters to ensure efficiency, reliability and low emissions.

Fuel temperature sensor functions

1. Calculating fuel density:

   • The temperature of the fuel affects its density. Higher temperature fuel is less dense, which means that there is less energy in the same volume of fuel.
   • The ECU uses the information from the temperature sensor to adjust the amount of fuel injected according to the density, ensuring the correct air-fuel mixture.

   Fuel injection optimization:

   • Accurate fuel temperature allows the ECU to adjust injection timing and pressure to improve the combustion process and prevent engine damage.

2. Exhaust gas control:

   • Incorrect fuel quantity and temperature may result in incomplete combustion, which is included in the exhaust gases. The temperature sensor helps to completely eliminate emissions. 

3. Improving engine performance and efficiency:

   • Fuel injection optimized for the appropriate temperature improves engine performance, reduces fuel consumption and helps the engine run smoother.

   Preventing engine overheating:

   • If the fuel is too hot, it can cause a vapor lock effect, where fuel vapors block the flow of fuel. The sensor helps detect critical temperatures and adjusts the system to prevent this.

   Fuel system protection:

   • High fuel temperatures can damage fuel injectors and the high-pressure pump, especially in diesel engines. Temperature monitoring can protect the system from excessive load.

The principle of operation of the fuel temperature sensor

• The sensor usually works using a thermistor, which changes its electrical resistance according to the fuel temperature.
• Thermistor operation:
  • Cold temperature: High resistance.
  • Warm temperature: Low resistance.
• The ECU reads this changing resistance and interprets it as fuel temperature, using it to control the engine.

Fuel temperature sensor location

• The fuel temperature sensor is usually located:
  • In diesel engines: At the Common Rail or high pressure pump.
  • In gasoline engines: In the fuel line or just before the injectors.

Problems and signs of malfunction

A malfunction of the fuel temperature sensor can cause problems in engine operation:

1. Incorrect fuel quantity:

   • If the sensor is sending incorrect data, the ECU may inject too much or too little fuel.
   • The result is uneven engine performance or increased fuel consumption.

   Decreased engine performance:

   • An incorrect air-fuel mixture causes a decrease in engine performance.

2. Rich mixture or incomplete combustion:

   • Incorrect temperature detection causes incomplete combustion of the fuel, which results in increased exhaust emissions and the formation of soot particles.

3. Check Engine Light:

   • The ECU may detect a sensor failure and activate the fault light by storing a fault code that refers to the fuel temperature sensor.

Maintenance and replacement

• If the fuel temperature sensor is faulty, it must be replaced. The sensor is usually easily accessible and relatively inexpensive.
• Regular fuel system maintenance, including clean fuel and timely filter replacement, will help prevent sensor failure.

Summary

The fuel temperature sensor is an important component that ensures the efficient operation of the fuel system. It measures the temperature of the fuel, allowing the ECU to optimize the injection amount, timing and pressure. This improves engine performance, reduces emissions and protects the fuel system from overheating. In the event of a failure, it is important to replace the sensor quickly to avoid engine malfunctions.

 

Fuel Pressure Sensor

The Fuel Pressure Sensor is an important component that measures the pressure within the fuel system. The main function of this sensor is to ensure that the fuel pressure remains optimal in the engine to achieve efficient fuel injection and engine operation. The pressure sensor is used in both diesel and gasoline engines, but its role is particularly critical in Common Rail diesel engines and direct injection gasoline engines.

Fuel pressure sensor functions

1. Fuel pressure monitoring:

   • The sensor measures the fuel pressure in the fuel rail (Common Rail) or fuel line.
   • This ensures that the pressure corresponds to the engine operating mode (idle, acceleration, load, etc.).

   Data transmission to ECU:

   • The pressure sensor signal is transmitted to the engine control unit (ECU), which uses this information to adjust fuel injection.
   • The ECU ensures that fuel is injected at the correct pressure, improving combustion and fuel economy.

   Fuel pressure adjustment:

   • If the pressure is too low or too high, the ECU adjusts the high-pressure pump, pressure regulator, or changes the injection parameters.

   Fuel consumption optimization:

   • The correct pressure allows the ECU to ensure the precise amount of fuel is injected, improving the engine's fuel efficiency.

2. Ensuring engine performance:

   • For engine performance and smooth operation, it is important that the fuel pressure is appropriate in different driving modes (e.g. when accelerating or climbing hills).

3. Exhaust gas control:

   • Using a pressure sensor, the ECU can ensure complete combustion, which helps reduce exhaust emissions and meet environmental requirements.

4. Protection for high-pressure systems:

   • In diesel engines, the pressure sensor protects the high-pressure pump and injectors from excessive pressure, which can cause damage to components.

The working principle of the fuel pressure sensor

• The sensor usually works using a piezoelectric element or a strain gauge that measures the pressure inside the fuel system.
• The pressure sensor converts the measured pressure into an electrical signal that the ECU interprets and uses to control the fuel injection and pressure regulators.

Fuel pressure sensor location

• In diesel engines: Usually located in the Common Rail system or near the high pressure pump.
• In gasoline engines: Located in the fuel line or at the outlet of the high-pressure pump.

Problems and signs of malfunction

A faulty fuel pressure sensor can cause serious engine problems. A faulty sensor will send incorrect information to the ECU, which can lead to incorrect fuel injection parameters.

1. Decreased engine performance:

   • Incorrect pressure can cause the engine to lack power, run unevenly, or stall.

2. Uneven idle:

   • If the pressure is not stable, the engine may idle unevenly or stall.

3. Increased fuel consumption:

   • Due to incorrect pressure, the ECU may inject too much or too little fuel, increasing fuel consumption.

4. Increase in exhaust gases:

   • Inaccurate pressure causes incomplete combustion, which increases exhaust emissions and can damage the catalytic converter or diesel particulate filter (DPF).

5. Check Engine Light:

   • The ECU detects a problem with fuel pressure and activates a warning light. Errors can be related to pressure problems or sensor failure.

Fuel pressure sensor maintenance and replacement

• If the pressure sensor is faulty, it must be replaced. A faulty sensor can cause the entire fuel system to fail.
• Regular fuel system maintenance, including changing filters and using clean fuel, will help prevent damage to the pressure sensor.

Summary

The fuel pressure sensor plays a critical role in ensuring the correct fuel pressure under various engine operating conditions. This helps optimize fuel economy, improve engine performance, and reduce emissions. A failure of the pressure sensor can cause serious problems in engine operation, so it is important to ensure that it is in good condition and replaced promptly if necessary.

Fuel Pressure Regulator Valve

The Fuel Pressure Regulator Valve is an important component of the fuel system, whose function is to maintain the fuel pressure at the desired level, according to the engine operating mode and load. This is critical in both gasoline and diesel fuel systems, especially in Common Rail systems, where the fuel pressure can reach very high values.

Main functions of the fuel pressure control valve

1. Maintaining fuel pressure:

   • The valve keeps the fuel pressure stable, regardless of engine load or changes in fuel flow.
   • This ensures that the injectors always receive fuel at the correct pressure.

   Adjusting the pressure according to the needs of the engine:

   • When the engine is running at low load (e.g. idling), the fuel requirement is lower. The control valve reduces the pressure to save fuel and prevent excessive pressure in the system.
   • Under high load (e.g. accelerating), the valve increases the pressure to ensure sufficient fuel flow and performance.

2. Fuel overflow control:

   • If the fuel pressure exceeds the required level, the control valve directs the excess fuel back into the fuel tank or back into the system (depending on the design).

   Fuel system protection:

   • The control valve prevents excessive fuel pressure from rising, which could damage the high-pressure pump, fuel rail, injectors or other components.

3. Optimizing fuel consumption and efficiency:

   • The correct pressure improves the combustion process, which in turn reduces fuel consumption and exhaust emissions.

4. Ensuring engine performance and smooth operation:

   • Stable and correct pressure ensures smooth fuel supply and consistent engine operation under all operating conditions.

The working principle of the fuel pressure control valve

The control valve operates electronically or mechanically:

1. Mechanical control valve:

   • In mechanical systems, the valve is equipped with a spring that opens or closes the valve according to the pressure. When the pressure exceeds a certain limit, the valve opens the overflow hole and directs the excess fuel back into the tank.

   Electronic control valve:

   • In electronic systems (e.g. Common Rail diesel engines), the valve is controlled by the engine control unit (ECU). The ECU analyzes data from the fuel pressure sensor and adjusts the control valve as needed.

Location of the fuel pressure control valve

• In diesel engines: Usually located at the outlet of the Common Rail high-pressure pump or near the injectors.
• In gasoline engines: Often located in the fuel line or just before the injectors.

Signs of a fuel pressure control valve malfunction

In the event of a malfunction, the valve cannot maintain fuel pressure within the correct range, which causes problems in engine operation:

1. Decreased engine performance:

   • Insufficient fuel pressure causes a drop in power and difficulty accelerating.

2. Uneven engine operation:

   • If the pressure fluctuates, the engine may run unevenly, for example at idle.

3. Increased fuel consumption:

   • Incorrect pressure leads to incorrect fuel injection, which increases fuel consumption.

4. Engine stop:

   • If the pressure is too low, the engine may stall or not start.

5. Increase in exhaust gases:

   • Incorrect pressure can cause incomplete combustion and increase the release of soot or other harmful particles.

   Check Engine Light:

   • The ECU detects a pressure problem and activates a warning light, storing a fault code, which often indicates a control valve failure.

Maintenance and replacement

Maintenance:

• The control valve does not usually require regular maintenance, but the cleanliness of the entire fuel system is important to ensure its proper operation. Timely replacement of fuel filters and the use of high-quality fuel will extend the life of the valve.

Replacement:

• If the valve is faulty, it must be replaced. Electronic control valves can be more expensive and require specialist assistance.

Summary

The fuel pressure control valve plays a critical role in regulating the pressure in the fuel system, ensuring the engine runs efficiently and smoothly. The valve helps maintain the correct pressure according to the engine's needs, improving fuel economy and reducing emissions. Its failure can cause serious problems in engine operation, which is why it is important to monitor its condition and replace it quickly if necessary.

 

Fuel Delivery Module (FDM or Fuel Pump Module)

The Fuel Delivery Module (FDM), also known as the Fuel Pump Module, is a component of a vehicle’s fuel system responsible for delivering fuel from the fuel tank to the engine. It typically includes a fuel pump, a fuel level sensor, and sometimes a fuel filter. Its purpose is to ensure that the engine receives the correct amount of fuel at the proper pressure and flow required for efficient operation.

Main Components of the Fuel Delivery Module

Fuel Pump: A pump that moves fuel from the fuel tank to the engine.

Fuel Level Sensor: Measures the amount of fuel in the tank and sends this information to the vehicle’s fuel gauge.

Fuel Filter: Removes dirt and particles from the fuel that could damage the engine or fuel injectors.

Module Housing: The structural casing that holds all module components together inside the fuel tank.

Functions of the Fuel Delivery Module

Fuel Delivery: Pumps fuel from the tank into the engine’s fuel system where it mixes with air and is ignited.

Maintaining Proper Pressure: Ensures that fuel is delivered to the engine at the correct pressure.

Fuel Level Monitoring: Allows the driver to see how much fuel remains in the tank.

Fuel Filtration: Protects the fuel system and engine components from contaminants.

 

Fuel Pressure Regulator

The Fuel Pressure Regulator is an important component in gasoline engines that maintains consistent and correct fuel pressure in the fuel system. Its purpose is to ensure that fuel reaches the fuel injectors at the proper pressure, allowing the engine to operate efficiently and smoothly.

Function of the Fuel Pressure Regulator in a Gasoline Engine

Fuel Pressure Regulation: The regulator maintains the fuel pressure at an optimal level required for proper engine operation. If the pressure becomes too low or too high, it can cause an incorrect air–fuel mixture and engine performance problems.

Returning Excess Fuel: When fuel pressure exceeds the required level, the regulator directs excess fuel back to the fuel tank. This prevents system overload and improves fuel efficiency.

Adjusting Pressure According to Engine Load

• Vacuum-Controlled Regulator (older systems): Adjusts fuel pressure according to engine vacuum. For example, during heavy load or acceleration, the regulator increases fuel pressure to provide more fuel.
• Electronically Controlled Regulator (modern systems): The ECU (Engine Control Unit) controls fuel pressure more precisely based on real-time engine data.

Location of the Fuel Pressure Regulator

Older gasoline engines: Usually located at or near the end of the fuel rail.

Modern fuel systems: Often integrated into the fuel pump module inside the fuel tank.

Fuel Pressure Regulator Failures and Symptoms

If the fuel pressure regulator is not working properly, the following problems may occur:

Reduced Engine Performance: Low fuel pressure may cause poor acceleration and loss of power.

Increased Fuel Consumption: Excessively high fuel pressure can cause the engine to use more fuel than necessary.

Difficulty Starting the Engine: Incorrect fuel pressure may make starting the engine difficult.

Black Smoke from the Exhaust: An improper air–fuel mixture may result in excessive fuel combustion.

Fuel Smell: If the regulator leaks, a fuel odor may be noticeable around the engine.

Maintenance and Replacement

Inspection: If a faulty regulator is suspected, fuel pressure can be checked using a fuel pressure gauge.

Replacement: A defective regulator should be replaced. While the procedure is usually not very complex, some vehicles require special tools, especially in modern systems where the regulator may be located inside the fuel tank.

Gasoline Engine and Diesel Engine: Fuel System Comparison

Gasoline engine fuel system

Gasoline engines work by using a spark to ignite the air-fuel mixture in the cylinder. The fuel system of a gasoline engine is designed so that the fuel is sprayed into the intake manifold or directly into the cylinder, where it mixes with the air.

Types:

• Port injection: Fuel is sprayed into the intake manifold before entering the cylinder.
• Direct injection: Fuel is injected directly into the cylinder, providing better combustion efficiency.

Advantages:

1. Faster response: Gasoline engines typically have faster acceleration.
2. Smoother operation: Runs quietly and without much vibration.
3. Lower NOx emissions: Gasoline engines produce fewer nitrogen oxides than diesel engines.
4. Easier maintenance: Maintenance costs are often lower because the system is simpler.

Disadvantages:

1. Higher fuel consumption compared to a diesel engine.
2. Shorter engine life due to increased wear.

 

Diesel engine fuel system

Diesel engines use compression ignition – high pressure causes the fuel to burn without a spark. Modern diesel engines mostly use the Common Rail system, which allows for high-pressure fuel injection and multi-stage injection.
Working principle: Diesel fuel is sprayed directly into the cylinder under high pressure (2000–2500 bar), where it mixes with air and ignites under the influence of pressure.
Advantages:

1. Better fuel economy: Diesel engines use less fuel, especially over long distances.
2. More torque: Provides better performance in difficult conditions and at low revs.
3. Longer life: Diesel engines are generally more durable and last longer.
4. Suitable for larger vehicles: Effective for heavy loads and long distances.

Disadvantages:

1. Higher maintenance costs as the system is more complex and requires special maintenance.
2. Higher NOx emissions and soot particles, although modern diesel cars use exhaust gas cleaning systems (e.g. DPF and AdBlue).
3. Runs louder and vibrates more than a petrol engine.

Main differences between a gasoline engine and a diesel engine

Attribute	Gasoline engine	Diesel engine
Fuel consumption	Higher fuel consumption	Lower fuel consumption
Combustion method	Spark ignition	Ignition by pressure
Exhaust gases	Lower NOx but more CO2	Higher NOx, less CO2
Maintenance costs	Lower	More expensive (especially the Common Rail system)
Engine life	Shorter	Longer
Performance	Suitable for fast and light cars	Suitable for larger and heavier vehicles
Environmental impact	Lower soot emission	Higher NOx emissions

 

Which fuel system to choose?

1. The gasoline engine is suitable for:

   • For city driving and shorter distances.
   • If you prefer a quieter and smoother ride.
   • If you are willing to accept slightly higher fuel consumption.

2. Diesel engine is suitable:

   • If you often drive long distances.
   • If you need a vehicle that can carry heavy loads or is suitable for off-road driving.
   • If you are looking for lower fuel costs in the long term.

Fuel system maintenance tips

• Check the fuel filter regularly and replace it at the manufacturer's recommended intervals.
• Use high-quality fuel to prevent system blockages and damage.
• Keep an eye on the fuel system for leaks or loss of pressure.
• On diesel cars with a common rail system, have the injectors and high-pressure pump checked regularly.
• Pay attention to the warning signs on the dashboard, especially if there are problems with fuel pressure or mixture.

Summary

A car's fuel system is essential in any vehicle, and its type depends on the engine technology. A gasoline engine offers smooth and quiet operation, while a diesel engine is better in terms of fuel economy and durability. The choice depends on your driving style, needs and budget. In either case, a regularly maintained fuel system ensures efficient operation and extends the life of the engine.
 

Here you will find a range of fuel system tools.

Here you will find a range of fuel system cleaning additives.