The specifications of a high-pressure fuel pump depend on the specific model used in a given vehicle. In general there are two main types of fuel pumps: mechanical and electrical. There are also two iterations of electrical pumps on the market, including low- and high-pressure variants.
The mechanical fuel pump variant is more commonly seen in older vehicles, especially those that use a carburetor, and relies more on gravity and very low volumes of pressure to pump the fuel. Electrical fuel pumps, by comparison, apply a significantly higher amount of pressure per square inch to pump the fuel more efficiently. As of 2015, electrical fuel pumps are in higher demand than in previous years and used in most modern vehicles.
A 2001 to 2002 Acura CL electrical fuel pump has six cylinders and a 3.2-liter capacity that pushes about 40 to 60 pressure per square inch, which is considered high. A 1984 to 1987 model Audi 90 also features an electrical pump with only four cylinders and a 2.0-liter capacity with a lower pressure-per-square-inch rating. In addition, Walbro also has a universal electrical fuel pump, the GSS340, which features 80 pressure per square inch and pumps over 210 liters per hour.