A fuel pump is an essential component on a car or other internal combustion engined device. Fuel has to be pumped from the fuel tank to the engine and delivered under low pressure to the carburetor or under high pressure to the fuel injection system. Some fuel injected engines have two fuel pumps for this purpose: one low pressure/high volume supply pump in the tank and one high pressure/low volume pump on or near the engine. The fuel pump has three functions: to deliver enough fuel to supply the requirements of an engine under all operating conditions, to maintain enough pressure in the line between the carburetor and the pump to keep the fuel from boiling, and to prevent vapor lock. Excessive pressure causes the carburetor float needle off its seat its seat resulting in high fuel level in the float chamber, leading to high fuel consumption. Highest pressure occurs at idling speed and the lowest at top speed.