The function of the gasoline pump is to suck the gasoline out of the fuel tank and press it into the float chamber of the carburetor through the pipeline and the gasoline filter. It is thanks to the petrol pump that the petrol tank can be placed at the rear of the car away from the engine and below the engine.
Gasoline pumps can be divided into two types: mechanically driven diaphragm type and electric driven type.
Diaphragm gasoline pump is the representative of mechanical gasoline pump. It is used in carburetor engine and is generally driven by the eccentric wheel on the camshaft. Its working conditions are as follows:
① During the rotation of the oil suction camshaft, when the eccentric wheel moves the rocker arm and pulls down the pump membrane pull rod, the pump membrane descends, generating suction, and the gasoline is sucked out of the fuel tank, and passes through the oil pipe, the gasoline filter, and the oil entering the gasoline pump. room.
②Pump oil When the eccentric wheel rotates through a certain angle and no longer pushes the rocker arm, the pump membrane spring stretches, the push pump membrane rises, and the gasoline is pressed from the oil outlet valve to the float chamber of the carburetor.
The diaphragm type gasoline pump is characterized by a simple structure, but due to the thermal influence of the engine, special attention should be paid to ensuring the pump oil performance at high temperatures, as well as the durability of the rubber material diaphragm against heat and oil.
Generally, the maximum fuel supply of the gasoline pump is 2.5 to 3.5 times larger than the maximum fuel consumption of the gasoline engine. When the oil volume of the pump is greater than the oil consumption and the needle valve of the carburetor float chamber is closed, the pressure in the oil pump outlet pipeline increases, which reacts to the oil pump and shortens the diaphragm stroke or stops working.
Electric petrol pump
The electric gasoline pump is not driven by the camshaft, but repeatedly sucks the pump membrane by electromagnetic force. This kind of electric pump can freely choose the installation position and can prevent the phenomenon of air resistance.
The main installation types of electric gasoline pumps for gasoline injection engines are installed in the oil supply pipeline or in the gasoline tank. The former has a larger layout range, does not require a specially designed gasoline tank, and is easy to install and disassemble. However, the oil pump has a long oil suction section, which is prone to air resistance, and the working noise is also large. In addition, the oil pump must not leak. At present, this type of vehicle is rarely used. The latter has simple fuel lines, low noise, and low requirements for multiple fuel leaks, which is the main trend at present.
When working, the flow of the gasoline pump should not only provide the consumption required for engine operation, but also ensure that there is sufficient oil return flow to ensure stable pressure and sufficient cooling of the fuel system.