Tuesday, December 3, 2013
Kinds of Fuel Pumps
All engines have some source of energy (fuel), whether that energy is electricity, gasoline, hydrogen or some other source. And because all vehicles have engines, all vehicles therefore need an energy source. If the energy source is a liquid fuel such as gasoline, the design of the vehicle typically requires a way to get the liquid fuel from the gas tank to the carburetor and fuel system. In most vehicles, this method is the fuel pump. There are different types of fuel pumps, and what follows is an explanation of the different types and where theyre found.
Mechanical Pumps
Mechanical fuel pumps are one of the two main types of fuel pumps. These pumps are used on carburated engines. They are called mechanical pumps because they operate mechanically---meaning, their operation is dependent on the turning of a cam shaft, which manipulates a lever that pulls on a diaphragm; the diaphragm operates valves that allow fuel out of the tank and into the fuel system. These pumps are low-pressure pumps and operate at only about 4 to 6 psi. They typically are mounted on the engine.
Electric Pumps
Electric fuel pumps are the second main type of fuel pump. Theyre used on engines with fuel injection systems. These pumps dont require an eccentric cam on a cam shaft to operate, and they can operate at much higher pressures than mechanical fuel pumps. Most electric fuel pumps operate at 30 to 40 psi. Some fuel injection systems make use of two electric fuel pumps: One is mounted in the tank, and the other is mounted on or near the engine.
Turbo Pumps
A third type of fuel pump is not as well-known, because it is found only in jet and rocket engines. These pumps are called turbo pumps. They are centrifugal and get their propulsion from either a ram-air device or a gas turbine.
Safety
Of the two main types of fuel pumps, electric pumps are considered the safest. This is because they often make use of two separate devices. The first device is an electronic control unit (ECU), which is designed to stop the pump from operating in the instance of an accident. The second device is an inertia switch. This switch keeps the pump from operating if it senses that the vehicle has overturned. Also, the placement of the electric fuel pump within the gas reduces the risk of a fire, because liquid gasoline is less combustible than gasoline vapors.
Pros and Cons
There are pros and cons to both the main types of fuel pumps. Manual pumps can be easier and cheaper to replace than electrical fuel pumps, because the electrical pump has different components and is submerged in gasoline. However, electrical fuel pumps are more efficient than mechanical pumps due to their ability to run at higher pressures, and because they are becoming the standard type of pump on vehicles, the right electrical fuel pump may be easier to find if it needs replacing than a mechanical pump.
