pump at a
Shell station dyed with
Solvent Yellow 124 (indicated as "Polttoöljy"/"Brännolja"/"MPÖ"; primarily intended for non-road vehicles such as those used in the agricultural and construction sectors) A modern gasoline pump is divided into two main parts – an electronic "head" containing an
embedded computer to control the action of the pump, drive the pump's displays, and communicate to an indoor sales system; and a mechanical section which (in a self-contained unit) has an electric motor, pumping unit, meters, pulsers and valves to physically pump and control the fuel flow. In some cases the actual pump may be sealed and immersed inside the fuel tanks on a site, in which case it is known as a
submersible pump. In general, submersible solutions in Europe are installed in hotter countries, where suction pumps may have problems overcoming
cavitation with warm fuels or when the distance from tank to pump is longer than a suction pump can manage. In modern pumps, the major variations are in the number of hoses or grades they can dispense, the physical shape, and additional hardware for services such as
pay at the pump and attendant tag readers. Light passenger vehicles pump up to about per minute (the United States limits this to per minute); pumps serving trucks and other large vehicles have a higher flow rate, up to per minute in the UK Higher flow rates may overload the vapor recovery system in vehicles equipped with enhanced evaporative emissions controls (required since 1996 in the US), causing excess vapor emissions, and may present a safety hazard. Historically, gasoline pumps had a very wide range of designs to solve the mechanical problems of pumping, reliable measurement, safety, and aesthetics. This has led to some popularity in collecting antique dispensers, especially in the US.
Fuel nozzles Nozzles are attached to the pump with flexible
hoses, so they can reach the vehicle's filler inlet. The hoses are robust to survive heavy wear and tear, including exposure to weather and being driven over, and are often attached using heavy spring or coil arrangements to provide additional strength. A breakaway valve is also fitted to the hose so that the nozzle and hose will detach and fuel flow will stop if a motorist drives off with the nozzle still in the filler. Nozzles are usually color-coded to indicate which grade of fuel they dispense, but the color-coding differs between countries and even retailers. For example, a black hose and handle in the majority of Europe indicate that the fuel dispensed is diesel, and a green dispenser indicates unleaded fuel; the reverse is common in the
US, with green for diesel, yellow for
E85, and black, red,
white, and blue for other gasoline grades, which vary by gas station.
Misfueling Some nozzles are designed to prevent the motorist selecting the wrong fuel. The nozzle on diesel pumps is supposed to be larger so that it cannot fit into the filler pipe on a vehicle tank designed for gasoline. However, the larger diameter diesel nozzles are not an actual requirement, and many diesel pumps have been fitted with standard gasoline nozzles. Also, the nozzle for leaded gasoline is wider than for unleaded, and the fill pipe on vehicles designed for unleaded-only was made narrower to prevent misfueling. Some diesel fuel tanks are designed to prevent the wrong type of nozzle from being used.
Blending In some countries, pumps can mix two fuel products together before dispensing; this is referred to as blending or mixing. Typical usages are in a "mix" pump to add oil to petrol for
two-stroke motorcycles, to produce an intermediate
octane rating from separate high and low octane fuels, or to blend
hydrogen and
compressed natural gas (
HCNG). Retailers benefit by offering three grades of fuel while having to stock only two. This frees up both working capital and tank capacity and improves fuel turnover. ,
Florida Flow measurement The equipment must accurately measure the amount of fuel pumped.
Flow measurement is almost always done by a 4 stroke piston meter connected to an electronic encoder. though states set their own legal standards. The standard accuracy is 0.3%, meaning that a purchase may actually deliver between . The reference temperature for gasoline volume measurement is 60 °F or 15 °C. There are far fewer retail outlets for gasoline in the US today than there were in 1980. Larger outlets sell gasoline rapidly, as much as in a single day, even in remote places. Most finished product gasoline is delivered in 8,000- to 16,000-gallon
tank trucks, so two deliveries in a 24-hour period are common. Gasoline spends so little time in the retail sales system that its temperature at the point of sale does not vary significantly from winter to summer or by region. Canada has lower overall population densities and geographically larger gasoline distribution systems, compared with the United States. Temperature compensation at the retail level improves the fairness under those conditions. In the United States, each state has its own Department of Weights and Measure, with the authority to perform all testing and certification, issuing fines for non-compliance. For example, in 2007 Arizona found that 9% of all pumps were off by at least 2.5% (the threshold for fines), evenly split between overcounting and undercounting fuel. station in
Port Charlotte, Florida In many jurisdictions, regular required inspections are conducted to ensure the accuracy of gasoline pumps. For example, the
Florida Department of Agriculture and Consumer Services conducts regular tests of calibration and fuel quality at individual dispensers. The department also conducts random undercover inspections using specially designed vehicles that can check the accuracy of the dispensers. The department issues correction required notices to stations with pumps found to be inaccurate. Most other US states conduct similar inspections. In Canada, inspections are regularly conducted by the federal government agency
Measurement Canada. Inspection dates and test results are required, by law, to be displayed to consumers on a sticker on gasoline pumps. Under the 2011 Fairness at the Pumps Act, a vendor with a modified or poorly maintained dispenser can be fined up to $50,000. However, virtually all pumps that fail inspection in Canada do so for general calibration errors caused by use over time. Intentional modification for the purpose of deceiving consumers is extremely rare, as are prosecutions.
Hydrogen Hydrogen fuel dispensers in use on
hydrogen stations dispense by the kilogram. In the US, the
National Institute of Standards and Technology (NIST) specifies in Handbook 44 that the tolerance of the measurements is to be 2.0%. Worldwide regulations are discussed under
OIML R 139 (
compressed hydrogen). Hydrogen pumps may be regulated under terms drawn from an industry technical standard,
SAE J2601.
Communications components Technology for communicating with gasoline pumps from a
point of sale or other controller varies widely, involving a variety of hardware (
RS-485,
RS-422,
current loop, and others) and proprietary software protocols. In the past, this gave pump manufacturers
vendor lock-in for their own point-of-sale systems, since only they understood the protocols. An effort to standardize in the 1990s resulted in the
International Forecourt Standards Forum, which has had considerable success in Europe, but less elsewhere. By October 2017, all US gasoline pumps with credit card readers had to support
EMV payment. A year before this rule came into force, a third of 750,000 pumps needed upgrading at a cost of $6,000 to $17,000 each plus the cost of new EPOS hardware and software. With some software not expected to be ready, some
fleet cards not having
chip technology available in time, not enough technicians for the installations, and many businesses unable to afford the upgrade, it was predicted the conversion would take until 2021.
Automatic cut-off The shut-off valve was invented in
Olean, New York, in 1939 by Richard C. Corson. At a loading dock at the
Socony-Vacuum Oil Company, Corson observed a worker filling a barrel with gasoline and thought it inefficient. The sound of a toilet flushing later gave him the idea for a "butterfly float." After developing a prototype with his assistant, Paul Wenke, Corson gave the suggestion to the company who later filed for a patent in his name. The initial intent of the device was to "allow a person to fill more than one barrel [of gasoline] at the same time." This mechanism eventually developed into the modern gasoline pump cut-off valve. Most modern pumps have an automatic cut-off feature that stops the flow when the tank is full. This is done with an auxiliary sensing tube running from just inside the mouth of the nozzle to a
Venturi pump in the pump handle. A mechanical valve in the pump handle detects a change of pressure and closes, preventing the flow of fuel.
Other components A modern fuel pump will often contain control equipment for the
vapor recovery system, which prevents gasoline vapor from escaping to the air. In the UK, for example, any new forecourt with a predicted throughput in excess of 500 m3 per month is required to have active vapor recovery installed.
Early designs File:Petrol bowser Gundagai.jpg|Restored petrol bowser,
Gundagai, Australia File:Zapfsäule BP Wien.jpg|Fuel pump in
Vienna, Austria. File:Ömossa 31.jpg|A 1991 photograph of a fuel pump in
Ömossa village,
Kristinestad,
Finland. File:Petrol Pump, Quillan, France.jpg|Antique fuel pump in
Quillan,
France. File:Historische Zapfsaeule.jpg|Antique
diesel fuel pump located at
Roscheider Hof Open Air Museum,
Konz, Germany. File:Verschiedene Zapfsäulen Deutsches Museum.jpg|Display of various antique fuel pumps at
Deutsches Museum in
Munich, Germany. File:Alte Zapfsäulen 1X7A7980.jpg|Display of various antique fuel pumps at Retro Classics 2018 in
Stuttgart, Germany. File:Old-Gas-Pumps.jpg|Old
Soviet Union fuel pumps. File:G-Morcomb's Service Station Gas Pumps.jpg|Gasoline pumps once used at the historic Morcomb's Service Station in
Glendale, Arizona. Included is a 1918 Visi Bowl pump (left) File:MobilgasPumpsAntique09162007.JPG|Antique "
Mobilgas" pumps, manufactured by
Tokheim, located in
Wilton, Connecticut. File:Savannah Georgia gas pump.jpg|Antique gasoline pump from
Savannah, Georgia. File:SoulsbyServiceStation MtOliveIL.jpg|Two types of
Shell gasoline pumps at Soulsby Service Station in
Mount Olive, Illinois. File:Old Gas Pumps at 2012 GMAS.jpg|Four old-fashioned gasoline pumps at the 2012 Greater Milwaukee Auto Show. File:Wayne petrol pump, 1923, in 'BP' livery - Science Museum, London.jpg|Wayne pump from 1923 in BP livery, at the Science Museum, London File:Petrol bowsers, 1932-1935 slnsw.jpg|Union Motor Spirit Company petrol bowsers, Sydney, Australia, 1932-1935 == Regulation ==