Fuel Pump Construction

A fuel pump is an essential component of the fuel system on a car. Fuel pumps use in carbureted and injected engines. By the depending to where fuel pump are using, they divided on the different types of fuel pumps.

Purpose of Fuel Pump

The Fuel pump`s purpose is supply fuel from fuel tank to the engine cylinder. Fuel pump of modern injection systems must create the high pressure, so are often used Electrical fuel pumps.

Types of Fuel Pumps

  1. Low-pressure fuel pumps – is mounted on the carbureted engines outside the fuel tank;
  2. High-pressure fuel pumps – is mounted on diesel and injection engines.

The modern fuel injected engines often use electric fuel pumps, which are mounted inside the fuel tank.

A fuel pump draws petrol out of the fuel tank by a pipeline to the carburetor, so sometimes it names petrol pump. The mechanical pump has drive from an engine. And electric fuel pump is usually mounted near the tank or inside the tank.

How a mechanical fuel pump works

How a mechanical pump works

Mechanical pump`s actuating lever moves up and down during the working. When need to fill the pump chamber lever pulls the diaphragm down.  The return spring moves the diaphragm up to deliver fuel to the carburetor device. The mechanical pump has drive from an engine camshaft. As the camshaft turns, a camshaft`s cam passes forces lever up at the one end. The other end of the lever moves down and pulls the diaphragm by it. During the lever pulls the diaphragm down, suction process is created, that draws petrol along the fuel pipeline into the petrol pump through a valve. When the camshaft`s cam turns further, it doesn`t press on the lever, so the return spring   moves the lever back, and its pull on the diaphragm is relaxing. The lever doesn`t push the diaphragm up, and the spring pushes for it.

So the diaphragm can move up only by expelling fuel from the pump chamber. The first valve is one way, so the petrol cannot move back and moves to the carburetor through another valve.  The carburetor needle valve which mounted into the float chamber regulates admits the petrol as it needs.

In our time by the widespread adoption of electronic fuel injection are used electric fuel pumps. We will talk about electric fuel pumps in next paragraph.

How an electric fuel pump Works

How an electric pump Works

An electric pump has a diaphragm-and-valve construction, but the drive is a solenoid (an electromagnetic switch) instead of the camshaft. The electromagnetic switch provides the pull on the diaphragm. The solenoid acts on an iron rod that pulls the diaphragm down, drawing petrol into the chamber. At the end of its way the iron rod relaxing the pull on the diaphragm by forces apart a set of contacts.

When the return spring acts to diaphragm, it go up and pulls the rod away from the contacts; After this, contacts are close and so the solenoid pulls the rod and diaphragm down again.

Author: delfi

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