Fuel pump function and operation

Summary

This video provides an in-depth look at the fuel pump's crucial role in the engine’s fuel supply system. It explains how the pump works to deliver fuel under pressure, its types (positive-displacement and flow-type), and their respective characteristics. The video covers essential details such as fuel pump pressure, voltage requirements, and safety measures like the safety valve. It also highlights how the pump is integrated into modern vehicles, including the pump module in the fuel tank, along with maintenance tips, such as checking for fuel flow issues and replacing filters. Proper fuel pump operation is vital for smooth engine function.

Takeaways

• 😀 The correct operation of the engine relies on the accurate amount of injected fuel.
• 😀 The fuel supply system includes several components that work together to deliver gasoline for injection.
• 😀 The fuel pump's task is to distribute fuel from the tank to the fuel injectors.
• 😀 A properly functioning fuel pump ensures the engine receives the right fuel pressure for efficient injection.
• 😀 Fuel pumps must meet specific requirements, such as delivery volume, system pressure, and pressure at lower voltages for cold starts.
• 😀 The fuel pump operates using a DC electric motor with permanent magnets and a rotor with windings.
• 😀 Positive-displacement fuel pumps are noisy but deliver high pressure and flow at low voltages.
• 😀 Flow-type fuel pumps are quieter and less sensitive to air bubbles but have a maximum pressure of 4 bar.
• 😀 A non-return valve ensures that fuel doesn't flow back into the tank when the engine is off.
• 😀 The fuel pump includes a safety valve that opens when there’s a blockage, preventing damage from excessive pressure.
• 😀 The fuel pump can be located either inside or outside the tank, with newer systems placing the pump submerged in the fuel for better protection and cooling.

Q & A

What is the primary task of the fuel pump in an engine?

The fuel pump's main task is to distribute fuel from the tank to the fuel supply system, ensuring a sufficient amount of fuel with the correct pressure for efficient injection during all engine operating modes.

What are the essential requirements for a fuel pump to ensure the smooth operation of the injection system?

The fuel pump must meet the following requirements: delivery volume from 60 to 250 l/h, fuel system pressure between 300 to 600 kPa (3 to 6 bar), and the ability to create system pressure at 50-60% of nominal battery voltage for proper cold engine startup.

How does the fuel pump operate mechanically?

The fuel pump is a DC electric motor with permanent magnets in the stator. The rotor has windings powered via brushes and a commutator. When power is applied, the rotor turns and drives an impeller, which sucks fuel from the tank and pushes it through the system under pressure.

What is the difference between a positive-displacement pump and a flow-type pump?

Positive-displacement pumps directly feed the injection system, providing pressures greater than 4 bar and high delivery speed at low voltages. They are noisy and sensitive to air bubbles in the fuel. Flow-type pumps, used in high-pressure systems, are quieter, not sensitive to bubbles, and achieve a maximum pressure of 4 bar.

What types of impellers are used in positive-displacement fuel pumps?

Positive-displacement pumps use either a roller-cell impeller or an internal-gear impeller. In roller-cell pumps, metal rollers move within the impeller, creating chambers to suck and expel fuel under pressure.

What role does the non-return valve play in the fuel pump system?

The non-return valve ensures that fuel does not flow back into the tank after the pump is turned off. This is important for maintaining fuel pressure in the system, especially during engine restart.

Why is the safety valve important in a fuel pump?

The safety valve opens when there is a blockage in the fuel supply, relieving pressure by returning fuel to the tank. It prevents damage to the fuel supply system by preventing excessive pressure that could burst the supply hose.

How can you check if the fuel pump is receiving enough voltage?

To check if the fuel pump is receiving sufficient voltage, measure the voltage at the battery terminals and at the pump connection. The difference should be less than 1 volt to ensure the pump operates properly.

What is the difference between an externally mounted and submerged fuel pump?

Older systems used external fuel pumps, often mounted under the vehicle. These pumps were prone to rust, leakage, and corrosion. Modern systems use submerged pumps inside the tank, where they are protected from external damage and the fuel itself helps cool and lubricate the pump.

What is the function of the pre-filter in the fuel pump module?

The pre-filter serves as the first line of defense, preventing impurities and small particles from entering the pump. A clogged pre-filter can hinder fuel flow and make the engine difficult to run, requiring the module to be disassembled and cleaned.