The petrol fuel tank is one of the primary elements of the fuel system. It is a container which is used to store the petrol needed for internal combustion in the engine. 

The fuel tank is located on the opposite side of the vehicle to the engine for safety reasons.  Fuel tanks are normally manufactured from either welded sheets of steel or aluminium or blow moulded from high-density polyethylene plastic (HDPE).

The fuel tank will have a pipe that connects to it which is used to fill the tank with fuel and this is covered by a petrol flap or cap. The fuel tank usually has a sensor inside which tells the fuel gauge how much fuel is in the tank and the tank is also designed to minimise the amount of hazardous vapours escaping the tank. The fuel system also has a fuel pump attached either to the fuel tank in newer models, or to the engine in older vehicles. The pump is operated either by the car electrics or by the engine depending on where it's located. The fuel pump is attached to a pipe which draws petrol out of the fuel tank. This fuel pipe has a filter in it to take out any imperfections in the fuel. Good maintenance of the fuel filter is essential as any imperfections such as paint chips or dirt will cause the running parts of an engine to wear more quickly.  In some older vehicles this fuel is then sent to the carburettor to mix the fuel and air in correct proportions. Nowadays, it's much more common for this to be mixed in the engine itself with fuel injected in to the engine chambers and mixing with air generated by the pistons.  

Problems with the fuel system can cause major problems with the engine. Some issues can include excessive engine smoke or difficulty with the engine starting or loss of power. These are obvious signs that something is wrong, and should be investigated immediately. If the fuel tank has a leak or is damaged in any way it should be replaced as soon as possible. The petrol fuel tank is the ideal replacement part, specifically designed to be compatible with the make and model of your car.