At this particular time gasoline is commercially available in two blends in the U.S.: E10 and E85. E10 refers to gasoline that has been blended with a volume of 10 percent alcohol per gallon [V%]. E10 is the most commonly dispensed fuel. Excluding a few exceptions, all vehicles can operate on E10 blended gasoline.
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E85 refers to gasoline that has been blended with a volume of 85 percent alcohol per gallon [V%]. E85 was blended for use in Flex fuel vehicles. Flex fuel vehicles can operate on blended fuels from E10 up to E85.
The EPA has approved the use of E20 for vehicles manufactured from 2001 and newer, but due to ongoing lawsuits, dispensary issues and logistics, implementation of E20 is on hold.
The Letter E
The alcohol for use with internal combustion engines is called ethanol (Eethyl alcohol), and primarily is made from corn. Because ethanol is derived from feedstock that is grown, it is considered a renewable fuel. The ethanol blend dispensed at the pumps is regulated. The signage on the pump will display the volume content of ethanol per gallon [V%] of gasoline being dispensed. At the end of 2010, more than 90 percent of all gasoline sold in the U.S. was blended with ethanol.
Each ethanol molecule contains 35 percent oxygen. Blending ethanol to gasoline is adding a liquid oxygenator.
This article is a discussion of a vehicle operating “impaired” due to an excessive amount of alcohol in the fuel system of the vehicle. With the blended gasolines commercially available to the consumer, what type of vehicle do you think would be most affected by excessive alcohol, a flex fuel vehicle or a non-flex fuel vehicle?
With a non-flex fuel vehicle, the ideal alcohol percentage in the fuel should fall between 7 to 10 percent. If the alcohol percentage becomes greater, fuel control issues can result.
As a diagnostic technician, I am hired when the diagnosis becomes stalled or the vehicle has returned repeatedly for the same initial complaint. I am a strong believer of covering the basics and performing the simple tests that will give you a base line of the vehicle regardless of the system being diagnosed. This thought process can save valuable shop time and prevent replacement of known good components in an attempt to locate the root cause of the complaint. Let’s take a look at an example.
A Hungover Honda
A 2009 Honda CR-V was brought into a local repair facility with a customer concern of an illuminated Malfunction Indicator Lamp (MIL) preventing a yearly state inspection from being performed. The vehicle has a 2.4 liter engine with approximately 80,000 miles. During the diagnosis the technician finds a stored fuel trim control fault (P0171).
For a P0171 test to fail, the long term fuel trim (LTFT) and short term fuel trim (STFT) have had to had reached or exceeded a pre-programmed threshold set by the manufacturer (LTFT > 25 percent, STFT > 5 percent, for example).
The two screenshots (taken from the Honda factory scan tool) contain all the information I needed to verify the complaint.
The factory tool has guided fault help. Is excessive alcohol in the fuel supply listed under possible failures? Well, kind of if you read the “fuel does not meet O/M specifications” cause with a broad definition.