A fuel pump is an essential component in an automobile's fuel delivery system. In most of the vehicles we find engine located at the front-end of the vehicle and the fuel tank at the other end. The main function of fuel pump is to draw the fuel from the storage tank and force it to the engine.
Although some old designs do not require fuel pump, for many of the latest non-gravity based engines it is an essential component and is often termed as 'the heart of the vehicle'. In this article, we will discuss about the two basic types and the advantages of one over the other.
Types of fuel pumps
• Mechanical: There are two types of mechanical pumps – old style mechanical pumps and new style GDI pumps.
o Old style mechanical: They can be found in few old model engines that have carburetors. The pump draws fuel from the tank and pushes it to the carburetor when the engine is running. Their output pressure is quite low – 4 to 10 psi. These low pressure pumps are often mounted on the top of the engine.
o New style high pressure GDI pumps – The advent of Gasoline Direct Injection (GDI) systems which can deliver fuel at very high pressures has given rise to the high pressure fuel pumps driven by camshaft. These high pressure pumps can generate fuel pressure up to 2,000 psi and higher, which help the GDI engines to achieve improved fuel economy with high power output and reduced emissions.
• Electrical: Electrical fuel pumps are used in fuel injection systems (introduced prior to GDI system) to pump the fuel from the fuel tank to the injectors. They typically deliver fuel at 30-85 psi to the fuel injector, which then opens and sprays the pressurized fuel into the engine. Unlike old mechanical, electrical fuel pump is typically located in or near the fuel tank.
Today, a variety of electrical fuel pumps intended for various applications are available in the market, such as:
o Roller vane pumps: They are positive displacement pumps that consist of vanes / blades to push the gas through the pump. They are often used in large trucks and also in diesel powered cars.
o Turbine pumps: They are not positive-displacement pumps. They have an impeller ring attached to the motor, which has blades to push the fuel through the pump. This pump runs smoothly and quietly and is mostly used in the latest vehicles.
o Gerotor pump: This is another positive displacement pump which uses an offset rotor to deliver the fuel through the pump. They are used in passenger vehicles.
o Solenoid pumps: They use a piston which is activated by an electromagnetic coil to generate pressure and thus help the fuel flow. They have many applications and are considered as universal type of electric fuel pumps.
o Peripheral pumps: They have impellers which pull and push the fuel. This is the standard type of pump used in many vehicles. Although they work much quieter, they produce limited pressure.
o Brushless pumps: These pumps have a fuel inlet and outlet between which a fuel mechanism is positioned with an armature to pump the fuel under pressure from the inlet to the outlet. Brushless pumps are generally used in diesel engines.
• Advantages of electric over mechanical fuel pumps
o Smaller and lighter: Compared to the old style low pressure mechanical fuel pumps, electrical ones are small in size and light in weight. This compact size allows them to easily accommodate inside the fuel tank. Moreover, usage of small devices reduces the electrical load and thus, controls the fuel consumption. However, electrical pumps are bit expensive.
o Ability to deliver fuel at higher pressures: Old styled mechanical pumps deliver pressure of only 4 – 10 psi, electric pumps can deliver gasoline at pressures typically between 30 – 85 psi. Fuel injection system requires the gasoline to be delivered at high pressures. However, new style high pressure mechanical pumps used in GDI systems can deliver greater pressures as high as 2,000-3,000 psi.
o Improved safety: Fuel injection systems have a special device called Electronic Control Unit (ECU) which controls power to the fuel pump. It is specifically programmed to shut off the fuel pump if it detects low or zero zero pressure. This safety feature avoids the risk of fire in engine compartment in case of collisions or terminal failures. As mechanical fuel pumps lack this feature, electrical pumps are considered to be safer.
o Highly durable: The presence of pump inside the tank allows it to get cooled by the flow of the gasoline. This results overheating of the electric pump, which is an issue with mechanical pumps (as they are mounted on the top of the engine), and thus increases the life of the electric pump.
o Alleviating vapor lock issues: If the vehicle is left unused for some time, the liquid fuel inside the tank changes to a gaseous state and thus disposes the operation of fuel pump causing loss of feed pressure to the carburetor. Vapor locks are quite common in old fuel systems with low pressure mechanical pumps. But in case of electric pumps, as the pump is in the interior of the tank and runs cooler, the pump pressurizes the fuel lines and prevents vapor locks.
With the increased use of aftermarket fuel pumps many companies have started manufacturing various varieties. Purchasing them from a reputed and experienced manufacturer is always a good idea.