will start with the fuel tank. A fuel tank comes in many different sizes depending on how much space is available. Most cars and trucks have only one tank but some trucks have two. Fuel tanks can be made of 3 different things. These are pressed corrosion-resistant steel, aluminum, or molded reinforced polyethylene plastic. The fuel tank has internal baffles or surge plates to prevent the fuel from sloshing back and forth. If you hear splashing in the tank on acceleration or deceleration, this means that the baffles could be broken. All tanks have a fuel filler pipe, a fuel outlet line to the engine and a vent system. All catalytic converter cars are equipped with a filler pipe restrictor so that leaded fuel, which is dispensed from a thicker nozzle, cannot be introduced into the fuel system. All modern fuel tanks include devices that prevent vapors from leaving the tank. All fuel tank designs provide some control of fuel height when the tank is filled. This is achieved by using vent lings within the filler tube or tank. With this design only 90% of the tank is ever full, leaving 10% for expansion. Some vehicles have a over filling limiting valve to prevent overfilling of the tank.
Fuel is drawn from the tank by an in-tank or chassis-mounted fuel pump. The fuel pump is the device that draws the fuel from the fuel tank through the fuel lines, to the fuel filter and then to the engine’s carburetor or injectors. There are two types of fuel pumps: mechanical and electrical. The mechanical fuel pump is bolted on the side of the engine block or on the side of the cover of the timing gear. The electrical fuel pump is located inside or outside of the fuel tank.
The diagram below is of an electrical fuel pump.
Electric fuel pumps offer important advantages over mechanical pumps. Because electrical pumps maintain constant fuel pressure, they aid in starting and reduce vapor lock problems. There are four basic types of electric fuel pumps and they are: diaphragm, plunger, bellows, and impeller or rotary. In-tank electric fuel pumps are usually rotary type. The diaphragm, plunger, and bellows are usually called the demand style. This means, when the ignition is turned on that the pump begins operation. All types shut off automatically when the fuel line is pressurized. So when there is a demand for more fuel, then the pump gives more, and less for when less is needed.
After the fuel travels through the hoses it goes to the fuel filter. On fuel injected vehicles, the fuel filter is connected in the fuel line between the fuel tank and the engine. Many of these filters are mounted under the vehicle and others are mounted in the engines compartment. Most fuel filters contain a pleated paper element mounted in the filter housing, witch may be made from metal or plastic. On many fuel filters the inlet and outlet fittings are identified and the filter must be installed properly. Some fuel filters on carbureted engines have the inlet, the outlet, and also a vapor return tube. A restricted orifice is positioned in the return tube on the filter and a fuel line is connected from this tube to the fuel tank.
The carburetor is a device used to mix, or meter, fuel with air in proportions to meet the demands of the engine during all phases of operation. The amount of air and fuel that is delivered to the engine depends on the difference between the low pressure (vacuum) in the engine and the pressure of the outside air (atmospheric pressure). In a port fuel injection system, air and fuel are mixed in the intake manifold runners very close to the intake valve(s) of the combustion chamber. A carburetor barrel is a passageway or bore used to mix the air and fuel. It consists of the throttle plate, venture, and air horn. A one-barrel carburetor is used on small engines that do not require large quantities of air and fuel. A two-barrel carburetor has two throttle plates and two venturis. The area where the air comes into the carburetor is common on both barrels.