In case you haven’t heard, Flex Fuel technology is really starting to take off in the U.S., becoming more popular in late-model vehicles than technicians may realize. If you haven’t had any training on these vehicles, you may find some of the technical changes OEMs have made to the engines will alter the way you diagnose fuel-related problems.
For those of you who are not familiar with this engine technology, a “Flex Fuel” vehicle is one that has been modified at the factory to allow it to operate on a mixture of alcohol and gasoline. The vehicle’s modifications are not only likened to hardware differences in the fuel system, but there are also software differences in the PCM.
Are You Talking about Gasohol?
The alcohol of choice to use in a blended fuel is ethanol. Ethanol is made from distilled sugar cane, fermented corn and other such agricultural goods. You may have seen gas pumps that say “E85” on the sides of them. The “E” stands for “ethanol” and the “85” is the percentage of ethanol in the mixture (85% ethanol and 15% gasoline); E100 of course being pure ethanol.
You might also be familiar with the term “gasohol.” Technically speaking, E85 is not really gasohol. Yes, the idea is similar, but the mixture makes the difference. Gasohol was the name given to some E10 to E15 fuels in the early 1980s. In gasohol, the primary ingredient was gasoline, and alcohol was the additive. However in E85, gasoline is considered the additive. So technically, it’s not really gasoline, and it’s not “gasohol.” It’s an alcohol fuel with a gasoline additive. Just a piece of trivia for your customers if you get on the subject with them.
There is another type of alcohol — methanol — that can be used in such a blend. Methanol is derived from wood and paper waste products. That blend, of course, being M85. Much of this discussion can be applied to M85, however no auto maker currently supports its usage. So this discussion will be centered on E85.
A glance over Chart 1 reveals information as to why E85 may be the choice fuel over M85.
(Note: In this article, Ford Flex Fuel systems will be used for technical reference. Much of this technical data can be applied to other makes, but may not be identical. Be sure to consult your technical resources before servicing any Flex Fuel vehicle.)
The Pro and Cons
Because alcohols are electronically conductive and may cause corrosive impurities, they are more corrosive than gasoline. Alcohol also attracts moisture, which increases its corrosive tendencies.
Cold weather can pose an obstacle to E85 because ethanol doesn’t vaporize as quickly as unleaded gasoline. For the warmer regions, this may be a non-issue because E85 will have sufficient vaporization for temperatures down to 10° F (-12° C). If the vehicle operator wishes to use an alcohol fuel below 10° F, he or she should switch to E70 and/or add block heaters. E70 has a 30% unleaded fuel content. This added unleaded fuel produces more vapors in cold weather than E85. A major difference between gasoline and alcohol is that alcohol has no hydrocarbon atoms in it. Instead, it has oxygen atoms. The added oxygen atoms bring pros and cons to the combustion chamber. As a plus, the added oxygen helps support combustion. This means less air is needed, plus the burn is cleaner since there are fewer hydrocarbons in the combustion chamber. On the down side, the extra oxygen waters down the air/fuel mixture with more oxygen. So, to counteract that, the fuel mixture must be richened to a 9.8:1 ratio on E85. A 9.8:1 ratio is approximately 30% richer than a normal combustion mixture of 14.7:1 with regular gasoline.
Another characteristic of alcohol is that each atom has less heat energy than gasoline atoms. However, since there are more of them in that 9.8:1 ratio, there is more power generated per firing event. The 30% richer mixture far offsets the potential 3% to 5% power increase, though. Overall, this still results in a lower fuel economy. The price of the fuel is slightly lower per gallon, but more is consumed. Therefore, operator economy is not a benefit of E85. Benefits of E85 come from less toxic emissions, cleaner engines, less national dependency on foreign oil resources, and benefit to the economy of domestic agriculture.
Identifying a Ford Flex Fuel Vehicle
Important: This subtopic pertains only to Ford vehicles. You will have to review your technical information sources for other makes.
Many Ford Flex Fuel vehicles have an emblem found on the front fender that resembles a roadway with a green leaf hanging over it (see Photo 1). However, most of the newer models don’t have that emblem anymore.
Even if they don’t have the “green leaf” on the fender, they will have another label inside the fuel door that states “Ethanol Fuel or Unleaded Gasoline Only” (see Photo 2). However, in the event of a crash, it is possible that emblems may be forgotten to be reinstalled. Therefore, it’s important for you to be able to use other methods to identify these vehicles.
The VIN number is one of the best methods. As you know, the 8th digit in the VIN denotes the engine size and type.
Taurus/Sable: 1993-’98 VIN digit “1” is a Methanol/Gasoline FFV. No methanol vehicles were built after 1998. 1997 to 2005 VIN “2” is an Ethanol/Gasoline FFV. Take note that in the years 1997 and 1998, both E85 and M85 vehicles were built. The alcohol types between these two vehicles are not interchangeable. VIN “1” is Methanol/ Gasoline only, and VIN “2” is Ethanol/Gasoline only. There is no Methanol/Ethanol/ Gasoline application.
Ranger: 1999 to 2005-1/2, VIN digit “V” is an Ethanol/ Gasoline 3.0L OHV FFV.
Explorer/Mountaineer: VIN digit “K” is an Ethanol/ Gasoline 4.0L SOHC FFV.
The calibration code found in the door jam can also identify a Flex Fuel vehicle. If it has a prefix of “610 C,” then it’s an ethanol vehicle. If it has a prefix of “610 G,” then it’s a methanol vehicle.
Flex fuel vehicles will often have a special sticker added to the inside of the fuel door that states what types of alcohol are compatible.
Take note that, at this time, there are no four-cylinder or eight-cylinder Flex Fuel Ford vehicles. It’s important to remember that the 3.0L Duratec DOHC engine found in newer Taurus and Sable models uses a VIN digit “1,” however, it’s not an FFV. In addition, the 4.2L in the F-series and E-series vehicles uses a VIN digit “2,” however it’s not a FFV. “Z” is used on 6.8L Expedition CNG and 5.4L F-series CNG vehicles, also not to be confused with flex fuel.
Flex Fuel Theory and Operation Flex Fuel Sensor
The flex fuel sensor (featured on all Ford Flex Fuel models up to and including 2000) mounts in the high pressure fuel line in the engine compartment. It measures the fuel conductivity, temperature and its dielectric constant (the ratio of the amount of electrical energy stored in an insulator) to determine the alcohol content in the fuel. The flex fuel sensor sends a duty cycle to the PCM.
The frequency of that signal increases as the alcohol content increases (see Chart 2). On 1999 and prior Taurus models a “fuel mixer” also was used. A fuel mixer is a device that the fuel must pass through to ensure accurate readings from the sensor. The fuel mixer has the outward appearance of a fuel filter, and is mounted in the fuel line directly before the flex fuel sensor. Although it appears similar to a filter, inside it is just a dead-ended porous tube.
Engine Block Heater
The engine block heater is a common freeze plug-style heater. It’s intended to pre-heat the engine block to aid start up in very cold climates. The block heater is not always needed, however. The operator has the option of switching to E70 or even standard unleaded fuel if needed. So vehicles aren’t equipped from the factory with a block heater; it must be installed by either the dealer or other qualified repair facility as needed.
Fuel Pump, Tank, Filter, Injectors and Lines
Since alcohol promotes corrosion, all of the parts that contact the fuel must be alcohol compatible. This sometimes can mean they are not made from the same materials as their unleaded fuel counterparts. For example, the lines and filler neck on a FF vehicle are stainless steel. Since the FF vehicle requires more fuel, some flow differences may exist as well in the pump and injectors. Sometimes the fuel tank is larger to offset the shorter range per tankfull.
Naturally, any O-rings that seal the system are also alcohol compatible. If you are replacing any of these components be sure that you install the correct part for the application. If non-flex fuel components are installed onto a flex fuel vehicle, it can damage the component and the engine as well.
The flex fuel PCM has different programming strategies when compared to a standard gasoline vehicle.
First of all, the flex fuel PCM must be capable of distinguishing between the different types of fuel. The Ford PCM has two different methods of achieving this, dependent on the model year. On 2000 and prior models, the PCM measures input from the flex fuel sensor. On 2001 and later models, the PCM uses a software strategy referred to as “deductive refueling logic.”
Deductive refueling logic simply watches for a refuel event by monitoring the fuel level. At the startup immediately after refueling, the PCM then looks at the O2 sensors for a slightly different purpose than normal. It uses the sensors to determine what kind of fuel the driver put in the tank. If the PCM is currently running unleaded fuel strategies and suddenly “sees” a lean condition at that startup, it assumes E85 was added and then uses its trim calculations to determine the amount of alcohol in the tank. After it has that amount calculated, it then resumes its normal “view” of what is “rich” or “lean” in respect to the type of fuel it “thinks” is in the tank. If the driver is switching from E85 back to regular unleaded, the same is true. The only difference in the switch back to unleaded is that the PCM will now see a “rich” condition upon restart after a refuel condition.
After the PCM has determined what type of fuel is in the tank, it runs new strategies including different base injector pulse widths and different ignition timing curves that work with the percentage of alcohol inferred.
Diagnostics and Testing
When it comes to testing for a “rich” or “lean” condition, or the integrity of the flex fuel sensor, you need to know how to test the content of the fuel in the tank to find the percentage of alcohol. To perform the fuel/alcohol test, you will need a 25 ml clear graduated cylinder, a stopper to seal the top of it, some clean water and 20 ml of fuel sampled from the fuel tank (it’s easiest to use the vehicle’s fuel pump to push it out through the pressure test port). Refer to Chart 3 for these steps.
Step 1: While wearing protective gloves, fill the beaker (graduated cylinder) with 20 ml of fuel from the vehicle.
Step 2: Add enough clean water to the beaker to bring the total volume in the cylinder to 24 ml.
Step 3: Seal the top of the beaker and shake it enough to stir the mixture. Let it sit for three minutes undisturbed.
Step 4: At the end of three minutes, the alcohol and the water should have blended together and settled to the bottom. The gasoline will float to the top. Record the measurement on the side of the beaker where the water/alcohol mixture meets the gasoline.
Step 5: Calculate the percentage of alcohol using this formula: (A-4)x5. The answer is the percentage of alcohol in the tank. For example: If the reading on the side of the beaker is 18 ml where the gas and water meet, then 18 minus 4 times 5 equals 70% alcohol (E70). If the reading on the beaker is 10 ml, then 10 minus 4 times 5 equals 30% alcohol (E30). This test is accurate within a 10% tolerance.
Step 6: Dispose of the “test fuel” as contaminated fuel and wash your hands. If you have no environmentally responsible method of disposing of the test fuel, Ford states (in its training material) that it’s OK to pour the mixture back into the tank. The added water will be absorbed by the alcohol in the tank.
During this testing, you may notice that E85 is very weak in gasoline odor and pale in color compared to typical gasoline. That is a normal characteristic of E85. The higher the alcohol content, the clearer and weaker the mixture appears to the senses.
Once you know the actual percentage of alcohol in the tank, it’s pretty straight-forward from here. Access the “Flex Fuel Index” PID on the scan tool. See if the FF index agrees with your calculations within 10%. If it does, then any “rich” or “lean” codes are not a product of the PCM using the wrong strategy. Normal diagnostics can resume as if the vehicle were the same as a dedicated gasoline vehicle. If the flex fuel index does not match, then this may be the cause of your “rich” or “lean” codes.
If the PCM underestimates the alcohol content, a “lean” condition will result (the PCM will be commanding high fuel trims). If the PCM overestimates the alcohol content, then a “rich” condition will result (the PCM will be commanding low fuel trims).
If the flex fuel index is incorrect on a system using a flex fuel sensor, then pinpoint testing of the flex fuel sensor will be required, possibly ending in replacement of the flex fuel sensor. If the flex fuel index is incorrect on a system using “Deductive Refueling Logic,” then clear the KAM and restart to see if the PCM relearns the correct flex fuel index. If it does, then the problem was likely due to an improper refueling practice. Generally, this is caused by the customer not turning the key off during refueling. It’s possible however, to have a faulty fuel level sensor cause an intermittent error in the PCM’s alcohol calculation. If it again relearns an incorrect value, then this may be caused by a vacuum leak, faulty MAF sensor, lazy O2 sensors, or anything else that makes the PCM “see” or “think” it “sees” a lean condition.
I would certainly hope that telling people not to drink ethanol fuel is a given, however… Pure ethanol is indeed the same as the grain alcohol found in liquor, beer and wine. There is an agent, called a “denaturant,” added to the pure fuel ethanol before it’s made into E85. This chemical agent is intended to make the pure fuel ethanol bitter tasting. This denaturant usually contains between 2% to 5% unleaded gasoline. When the denaturant is added to the ethanol, the mixture is now called “denatured ethanol.” It is deadly poisonous.
The main reason for mentioning the above is to warn anyone who is taking medication for the treatment of alcoholism such as “Anabuse” or some other disufiram. The vapors from E85 or even skin contact can cause the same adverse reaction as drinking beer, liquor or wine. In especially sensitive individuals who are on such medication, serious personal injury could result.
For the rest of us, the same rules apply with E85 as does regular gasoline. It’s an explosive, poisonous carcinogenic. Avoid the vapors, eye contact and prolonged skin contact, and do not ingest.
Ethanol, alcohol used in transportation fuels, is a high octane, liquid, domestic and renewable fuel, produced by the fermentation of plant sugars. It is typically produced from corn and other grain products, although in the future it may be economically produced from other biomass resources such as agricultural and forestry wastes or specially grown energy crops.
“The transition between methanol and ethanol in our cars should be very smooth,” said Phil Casey, IRL’s senior technical director. “Our cars won’t sound differently, smell differently or run differently than they have in the past. There will be a seamless transition from methanol to ethanol in our cars.”
Its high octane rating delivers strong engine performance by helping engines resist detonation so they can run higher compression ratios.
Race car engines operating on ethanol have demonstrated excellent performance due to the fuel’s high octane content. IndyCar Series cars have run on methanol fuel since the late 1960s. IRL reported that internal dynamometer testing has shown that there are no technical barriers to replacing methanol with ethanol.
The 2006 season will not be the first time ethanol fuel has powered a car in the famed Indianapolis 500. At the 1927 race, a car driven by Leon Duray was fueled by ethyl (grain) alcohols.
More IndyCar News:
Source: Honda IRL Racing
|Flexible Fuel Vehicle Facts
In model year 1998, manufacturers began making flexible fuel engines standard equipment on certain makes and models. A flexible fuel vehicle (FFV) is specially designed to run on any ethanol blend up to 85% ethanol. Special onboard diagnostics “read” the fuel blend, enabling drivers to fuel with E85 or gasoline in any combination from a single tank. There are no switches to flip, no mixing or blending. The computer adjusts the FFV’s fuel injection and ignition timing to compensate for the different fuel mixtures.
The following are some of the Flexible Fuel Vehicles on the road. This list is expected to grow as the OEMs continue to utilize this engine technology.
Nissan: 2005-’06 – 5.6L Titan King Cab and Crew Cab
Mercury: 2006 – 4.6L Mercury Grand Marquis (2-valve); 2002-’05 – 4.0L Selected Mountaineers; 2001-’05 – 3.0L Selected Sables (look for “Road & Leaf” logo)
Mercedes-Benz: 2005 – 3.2L C320 luxury, sport sedan and sport coupe, 2.6L C240 luxury sedan and wagon; 2004 – 3.2L C320 sport sedan, wagon and sport coupe; 2003 – 3.2L C320 sport sedan
Mazda: 1999, 2001-’02 – 3.0L Selected B3000 pickups
Isuzu: 2000, 2001 – 2.2L Hombre pickup 2WD
General Motors: 2006 – 3.5L Chevrolet Impala (LS, 1LT and 2LT), 3.5L Chevrolet Monte Carlo (LS and LT models only); 2005-’06 – 5.3L Chevrolet Silverado and GMC Sierra half-ton pickups 2WD and 4WD, 5.3L Vortec-engine Chevrolet Avalanche, Suburban, Tahoe, GMC Yukon and Yukon XL; 2002-’04 – 5.3L Chevrolet Silverado and GMC Sierra half-ton pickups 2WD and 4WD, 5.3L Vortec-engine Suburban, Tahoe, Yukon and Yukon XLs; 2000-’02 – 2.2L Chevrolet S-10 pickup 2WD; 2.2L Sonoma GMC pickup 2WD
Ford: 2006 – 3.0L Taurus sedan and wagon; 4.6L Crown Victoria (excluding taxi and police units); 5.4L F-150; 4.6L Lincoln Town Car; 2005 – 4.0L Explorer Sport Trac; 4.0L Explorer; 3.0L Taurus sedan and wagon; 2004 – 4.0L Explorer Sport Trac; 2002-’04 – 4.0L Explorer (4-door); 1999-2004 – 3.0L Taurus LX, SE and SES sedan; 2001-’03 – 3.0L Supercab Ranger pickup 2WD; 1999-2000 – 3.0L Ranger pickup 4WD and 2WD; 3.0L Taurus LX, SE and SES sedan; Many 1995-’98 Taurus 3.0L (check manual)
Daimler Chrysler: 2003-’04 – 2.7L Dodge Stratus Sedan, 2.7L Chrysler Sebring sedan, 2.7L
Chrysler Sebring sedan; 2003-’03 – 3.3L Dodge Cargo minivan, 2.7L Chrysler Sebring Convertible and sedan; 2000-’03 – 3.3L Chrysler Voyager, 3.3L Dodge Caravan and 3.3L Chrysler Town & Country minivans; 2006 – 4.7L Dodge Durango, 3.3L Caravan and Grand Caravan SE; 2005-’06 – 4.7L Dodge Ram Pickup 1500 Series, 2.7L Dodge Stratus sedan, 2.7L Chrysler Sebring sedan; 2004-’05 – 4.7L Dodge Ram Pickup 1500 Series, 2.7L Dodge Stratus sedan, 2.7L Chrysler Sebring sedan; 1998-’99 – 3.3L Dodge Caravan, 3.3L Plymouth Voyager and 3.3L Chrysler Town & Country minivans.
Source: National Ethanol Vehicle Coalition
E10 (10% ethanol and 90% unleaded gasoline) is approved for use in any make or model of vehicle sold in the U.S. Many automakers recommend its use because of its high performance, clean-burning characteristics. In 2004, about one-third of America’s gasoline was blended with ethanol, mostly in this 10% variety.
E85 Effects on Gasoline-Only Engines
Though most E85 producers say that no problems should occur if a motorist mistakenly fuels a gasoline-only vehicle once with the alternative fuel. The largest difference between an E85-powered vehicle and a gasoline-powered vehicle is that their computer modules are meant to read different amounts of oxygen within the fuel. E85 contains a higher amount of oxygen than gasoline, so E85 compatible vehicles are made to read that higher amount. When a higher amount of oxygen is read by a gasoline-powered vehicle, the Check Engine light may illuminate.
In the past, there has been concern that ethanol caused injectors to plug fuel-injected vehicles. However, that theory was never proven. Earlier fuel injectors of the pintle design (1988-’93) could form deposits that changed the pattern of the injected fuel. This problem developed from injectors seeping fuel when the vehicle was not running. This formed carbon deposits on the pintle and caused even more leakage, and this could happen with any gasoline. Because of this problem, injectors in most vehicles have been re-designed around the popet style and all gasoline is required to carry a detergent component to alleviate the deposit problem.