A mechanical fuel pump is a simple yet essential component in older gasoline engines, responsible for pushing fuel from the tank to the engine. It works based on a diaphragm and camshaft interaction. Here's a breakdown:
1. The Basics:
* Diaphragm: A flexible, rubber-like sheet that acts as the heart of the pump.
* Camshaft: A rotating shaft with lobes that create a reciprocating motion.
* Pushrod: A rod connecting the camshaft lobe to the diaphragm arm.
* Fuel Inlet and Outlet: Ports that allow fuel to enter and exit the pump.
2. The Cycle:
1. Intake Stroke: The camshaft lobe pushes the pushrod, which in turn pushes the diaphragm arm downwards. This creates a vacuum inside the pump chamber.
2. Fuel Draw: The vacuum pulls fuel from the tank through the inlet port.
3. Pressure Build-up: As the camshaft rotates, the lobe releases the pushrod, allowing a spring to push the diaphragm upwards. This compresses the fuel and builds pressure inside the pump chamber.
4. Fuel Delivery: The pressure forces the fuel through the outlet port and into the engine's fuel lines.
5. Continuous Operation:
This cycle repeats continuously as the engine runs, ensuring a constant supply of fuel to the engine.
6. Advantages:
* Simple and Reliable: Mechanical fuel pumps are relatively simple in design and are known for their durability.
* Directly Driven: They are directly driven by the engine's camshaft, ensuring consistent fuel flow.
* No External Power: They don't require any external power source, making them ideal for older vehicles.
7. Disadvantages:
* Noise: Mechanical pumps can be noisy during operation.
* Wear and Tear: Like any mechanical part, they can wear out over time, requiring replacement.
* Limited Pressure: They generally have lower pressure output compared to electric pumps, which can be a concern for modern engines with high-pressure fuel systems.
Modern Alternatives:
While mechanical fuel pumps were common in older vehicles, modern cars typically use electric fuel pumps mounted in the fuel tank. These are quieter, more powerful, and offer greater flexibility in fuel system design.
In summary, a mechanical fuel pump uses a camshaft-driven diaphragm to create a vacuum and pressure cycle, drawing fuel from the tank and delivering it to the engine. While they are less common today, they remain a significant part of automotive history and demonstrate the fundamental principles of fuel delivery.
