Ethanol and Fuel Pumps
Since nearly 80% of common vehicle repairs are related to durability, it makes sense that some parts, like fuel pumps, water pumps, and starter motors, would need to be replaced periodically. When buying a replacement fuel pump, such as a motorcycle electric fuel pump, customers will often find that the fuel pump is promoted as being compatible with ethanol blended fuel. Why is this the case? Interestingly, a fuel pump's compatibility with ethanol blends has nothing to do with its ability to pump ethanol or ethanol blended fuel. Rather, a fuel pump's compatibility with ethanol blends is determined by its ability to sit in a fuel tank full of an ethanol blend without corroding.
What is Ethanol?
Ethanol is an alcohol. In fact, ethanol is the alcohol found in liquor, beer, and wine. Ethanol is formed by fermenting plant material, such as corn. This means that ethanol is a fully renewable fuel source when used in compatible engines.
What are Ethanol Blended Fuels?
Ethanol is blended with gasoline to create ethanol blends, such as E10 (which contains up to 10% ethanol) and E15 (which contains up to 15% ethanol). According to the U.S. government, all gasoline engines can operate on E10. Most vehicles that are newer than 2012 are able to run on E15. Flexible fuel vehicles are able to run on ethanol blends containing up to 85% ethanol (called E85).
Why is Ethanol Added to Gasoline?
Ethanol is added to gasoline for two primary reasons. First, the gasoline in E10 and other ethanol blends is, by definition, diluted. This means that vehicles running on ethanol blends consume fewer non-renewable resources. Most importantly for geopolitical reasons, ethanol can be produced entirely from American corn supplies, which means that vehicles running on ethanol blends are less dependent on foreign sources of oil. Second, the ethanol added to gasoline in ethanol blends is an oxygenate, which causes the gasoline to burn more completely thereby reducing particulates and carbon monoxide in vehicle emissions.
How Does Ethanol Affect In-Tank Fuel Pumps?
As most mechanics know, the in-tank fuel pump, such as a motorcycle electric fuel pump, was invented because fuel injectors require a steady, high pressure flow of fuel. By immersing the fuel pump in the fuel tank, the fuel pump has access to a steady source of fuel. Because the fuel pump pushes the fuel from the fuel tank rather than pulling the fuel from the fuel tank, vapor lock is minimized. Finally, the fuel pump is able to provide a high pressure flow necessary for fuel injectors, without overheating, because the fuel in the fuel tank cools the fuel pump. While it may seem counter-intuitive, in-tank electric fuel pumps, such as motorcycle electric fuel pumps, are less likely to cause a fire hazard simply because they are surrounded by fuel.
This necessarily leads to the question of how immersing a fuel pump in an ethanol blend rather than pure gasoline affects the fuel pump. Interestingly, the ethanol itself does not necessarily cause adverse effects to the fuel pump. Rather, ethanol, by its chemical nature, attracts water and water can cause corrosion. But even this is usually not enough to adversely affect fuel pumps. The primary culprit of fuel pump corrosion is acetobacter, a bacteria that converts ethanol into acetic acid when in the presence of oxygen such as that found in water and the air space at the top of a fuel tank. Acetic acid, as its name suggests, is acidic. In fact, acetic acid is the primary acid in vinegar. With these facts in mind, it becomes clear why replacement fuel pumps often specify that they are compatible with ethanol blends. Electric fuel pumps, whether a motorcycle electric fuel pump, ATV electric fuel pump, or any other in-tank fuel pump, must be made from materials that resist corrosion from acetic acid, water, and microbial activity.