With the new year came new U.S. Environmental Protection Agency (EPA) emission regulations for small engines. The new EPA “Phase 3” emission regulations impact OEMs, as well as distributors, dealers, repair shops, rental centers and end users. Last year, all small spark-ignition engines greater than 225cc were impacted. This year, the regulations include all engines smaller than 225cc. By the next year, all gasoline-powered equipment will need to be certified by the EPA.
All of these requirements are rolled into Title 40 of the U.S. Code of Federal Regulations under Sections 40 CFR 1054 and 40 CFR 1060.
What it’s about
To really understand how this affects consumers, it’s necessary to first take a look at what the regulations impact: evaporative emissions. When liquid gasoline turns into a vapor, which happens when it’s warmed, evaporative emissions result.
The California Air Resources Board (CARB) has regulated evaporative emissions from equipment powered by small gas engines for several years, although most agricultural and construction equipment has been exempt. These regulations went nationwide via the EPA in 2011 and expanded in 2012. According to the EPA, small engines will emit about one-third fewer hydrocarbons under the new standards.
The regulations aim to control running losses and permeation losses from fuel systems. Many people are surprised to learn just how much fuel vapor passes through the walls of untreated plastic fuel containers alone. Permeation is just one way in which fuel vapors are emitted, though. Evaporative emissions occur when an engine is running as well as through diurnal loss, when the engine isn’t running, due to daily temperature changes.
Each equipment builder must control evaporative emissions from fuel systems and get equipment certified with the EPA. This trickles down to the end user, who needs to be aware of how the changes accompanying the regulations effect the product they are using and servicing.
What it looks like
Some manufacturers have been ahead of the game in improving products to meet the standards. Those manufacturers employ a number of methods to control evaporative emissions, from special hoses to fuel caps on sealed fuel tanks to carbon canisters and vapor control valves. Here’s a breakdown of what that looks like inside any new equipment a consumer may purchase.
Hoses that come in direct contact with liquid gasoline must now be special low-permeation fuel hoses, which are manufactured specifically to limit the amount of fuel vapors that permeate through the hose wall. The hoses need to be kept free of kinks and obstructions to ensure good working order.
Under the changes, most fuel systems are now sealed, and vented fuel caps have been primarily replaced with sealed caps to prevent evaporative emissions. When a sealed cap is used, there will be different hose connections. In addition to the normal fuel hose connection at the bottom of the tank, there also will be a connection for the vapor hose at either the top or bottom of the tank.
There’s one exception to the sealed fuel cap on some small engines, though. In those cases, the fuel cap self-vents through a carbon canister. The canisters come in different shapes and sizes and may be anywhere on the equipment, which makes it difficult to identify. The best method for locating a carbon canister is to first look for the spot where the vapor hose connects to the engine intake system, and then work backward toward the fuel tank. If the vapor hose connects directly to the tank, there will be no carbon canister. If the vapor hose appears to first go to a box, that is most likely the canister.
The carbon canister works to absorb diurnal vapors. When the engine runs, an intake vacuum draws any vapor from the tank into the engine, where it is burned. After the engine is shut off, vapors continue to be emitted into the atmosphere due to temperature changes throughout the day. The carbon canister absorbs those vapors, and when the engine is started again, the engine intake vacuum will draw in fresh air through the carbon canister’s vent port and thus purge the stored vapors.