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E-85 Refueling Events


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#16 brims

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Posted 13 March 2009 - 10:28 PM

I have found some information in the Helm manual about this.

There's a chart which I'm just going to try to sum up. It says to measure the content with the J 44175 tool ($500) and compare that to the "fuel alcohol content parameter on the scan tool" - if the difference is over 15% and the measured content is greater than 15% alcohol to drain the fuel tank and fuel system, add E10 or less and run the vehicle until at least 1 liter of fuel is used, then measure the sample again with that pricey tool. If the measured content is less than 15% use the scan tool to reset the learned fuel composition to 3%. Then you need to reset the fuel trim values.

If the difference between the computer and the measured content is more than 15% and the measured content is less than 15% alcohol you just need to reset the learned fuel composition to 3% then reset the fuel trim values.

If the difference between the computer and the measured content is less than 15% you are fine.

Edited by brims, 13 March 2009 - 11:18 PM.

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#17 sparkstech

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Posted 14 March 2009 - 11:46 AM

Every month or so I recieve a PM asking me about this thread so I'm going to update it to answer the question I get in every one of these PM's.

Before you freak out and think your content may be off it can be checked. You will probably have to pay for this but it much cheaper than doing the initial relearn. I charge a half hour for this but I would under no circumstances expect to pay more than an hour of diagnostic time to just check the content. If repairs are necessary expect the price to climb substantially. I don't know if many aftermarket facilities have the necessary tools but every GM dealer should have them, they are manditory tools for every dealer. The dealer has a special tool that a fuel sample from your vehicle is poured into. A very low voltage is pulsed through the tool and an A/C frequency reading is taken from the tool. The frequency measured translates into an actual fuel alcohol content. Then we hook up the scan tool and look at the data list to see what the calculated fuel content is. If it is within 10% there would be no action required, you would not need to relearn anything.

If the calculated content is not withinn 10% an initial fueling event would need to be performed. This is not something that can be done at home. First the tank needs to be drained and dried, this is pretty difficult at home. But the thing that makes it reall not a diy event is that you will need the bi-directional scan tool to force the composition reset, not many of us have a $2,500 scan tool sitting in the garage. These are the steps we take to do the initial relearn event.

  • Drain the fuel tank.
  • A complete key cycle needs to occur when the fuel tank is drained to ensure the ECM/PCM recognizes a refueling event.
  • Key ON, engine OFF with drained fuel tank.
  • Key OFF, add at least 11 L (3 gal) of non-blended gasoline to the fuel tank.
  • Perform the Fuel Composition Reset using a scan tool.

Ok time for good news bad news. GM has released revised calibrations for some FlexFuel (E85 compatible) vehicles that will accept the introduction of gasoline/ethanol blended fuels with ANY ethanol concentration that falls between 0 and 85%. What does that mean to you, many of these vehicles have a recall to cover this new calibration and part of that recall is checking the content and adjusting it as necessary, all covered under the recall. To find out if your vehicle is covered contact your dealer with your VIN and current miles on the vehicle. You will still need to go by the refueling guidelines after the reflash it is just so the vehicle will accept fuel between 0-85% where before the reflash it would only recognize fuels between 0-10% or 85-90%.

Bad news, if it does not fall under the recall and testing shows that the learned and actual content is not withinn spec it will not be covered under warranty. The warranty is to cover manufacturer defects, this is not a defect. There is a section in the manual on how to refuel your vehicle, it isn't GM's fault if you didn't read your manual to know how your vehicle works. The purpose of my original post was to emphasize the importance and to shed some light to the how's and why's of the system.

Edited by sparkstech, 14 March 2009 - 11:49 AM.

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#18 CoryFount

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Posted 11 May 2010 - 01:01 PM

So what you are saying, is that GM, for the Flex Fuel Vehicles are using Algorithms to figure out the Stoichiometry of the fuel that has been placed inside of our tanks??? Well Riddle me this, I have been using e-10 since i bought my 09GMC SLT Sierra FFV.... and it is commanding 13.74 normally... and the Stoich of E-10 is about 14.2.... I do belive that is alot larger than the 10%margin error that you speak of.
Wasn't Gm using an inline fuel separator in the first FFV's? Should i get this "refueling Event" reset??

Edited by CoryFount, 11 May 2010 - 01:03 PM.

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#19 drpepperrocks

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Posted 30 July 2010 - 11:31 AM

Wouldn't driving a couple of tankful's of E10 through it basically reset the computer to the correct E10 settings?

Drive til your running on fumes for each tank and then refill completely. Since the computer is sensing the content after a fill, it would eventually (after 3-4 tankfuls) sense nothing but the E10.

????

Why would you need to reset the computer if it updates the readings after every fill???

#20 Nick The Great

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Posted 30 July 2010 - 01:00 PM

I'm no chemist or mechanic, and haven't stayed at a Holiday Inn for a few months but the refill event shouldn't need to be performed after EVERY fillup. Just when you get a 'different' type of fuel. I.e. you switch from E10 to E85. Or E85 to E0. Etc.

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#21 brainpause

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Posted 11 February 2011 - 09:40 PM

So what you are saying, is that GM, for the Flex Fuel Vehicles are using Algorithms to figure out the Stoichiometry of the fuel that has been placed inside of our tanks??? Well Riddle me this, I have been using e-10 since i bought my 09GMC SLT Sierra FFV.... and it is commanding 13.74 normally... and the Stoich of E-10 is about 14.2.... I do belive that is alot larger than the 10%margin error that you speak of.
Wasn't Gm using an inline fuel separator in the first FFV's? Should i get this "refueling Event" reset??


+/- 10% of 13.74 is 12.37-15.11, so 14.2 is well within the range.

Or, +/- 5% of 14.2 is 13.49-14.91.

So, it appears to meet spec, looking at it from 2 different perspectives.

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#22 bigbeds

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Posted 13 February 2011 - 06:38 PM

great post, I'll pass this info down the line...maybe I should keep my old 92 Ford after all. :lol:
OK..here comes a stupid question...can the computer get fouled up if you switch from low to high octane e-10..out here in pennsy low octane is 87 and high is 94...and what about fuel additives???? octane boosters, line dryers, STP...and whatever else u can think of??
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#23 Spawn

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Posted 05 March 2011 - 08:56 AM

Here is what I don't quite understand. This info is in the owners manual. I tried E85 the other day because I found out where a pump was located in a state I had to travel to anyway for work. I followed the procedure exactly as it states in the owners manual. Instead of 7 miles, though, I drove 150 getting back home. The MPG was for crap, so when I got within 25 miles of being home, and down to a 1/4 of a tank, I followed the procedure again, but with regular gas this time. My MPG still sucks and is not near as good as it was pre-E85 fill up.

That sounds like a GM warranty problem to me. Will they not do the fix procedure under warranty in this case? This thread says to do it properly, the owners manual says to do it properly, I then do it properly, and it doesn't work right!

What a load of crap.
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#24 dsch

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Posted 08 April 2011 - 09:52 PM

My truck had recently had trouble with hard starts while cold and running rich codes. Took it into the dealer and the tech told me that the computer was expecting fuel with a higher alcohol content than was in my tank ( I only use ethanol free ESSO fuel). The dealer fixed it under warranty.

#25 terzmo

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Posted 28 April 2011 - 08:10 AM

My truck had recently had trouble with hard starts while cold and running rich codes. Took it into the dealer and the tech told me that the computer was expecting fuel with a higher alcohol content than was in my tank ( I only use ethanol free ESSO fuel). The dealer fixed it under warranty.



computers....special tools....reasons why the small time mechanics and backyard mechanics are disappearing and soon the only place for service and repairs will be the "DEALER".

In the 50's/60's I could tear an engine down and set it up with a hundred dollars worth of tools. AND still get 12 to 16 MPG....My how We have progressed.

#26 Surfer_Nick

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Posted 21 September 2011 - 01:47 PM

Ok, so I've read this whole thread 2x...and I understand most of it, yet still have a few question.

1) I've run my 08 Silverado w/ 5.3 iron FF engine exclusively on e10 since new. There are 43000 miles on it now. If I were to burn through 7/8 of a tank and fill up following the proper refueling procedure with e85, then go back to e10 after that tank, I'm assuming I'll neeed to do the refill procedure again and drive 7+ miles so the computer relearns the tank contents. If I were to stick with e10 exclusively after that, do I have to drive 7+ miles after each refuel?

2) Is my vehicle entitled to that reflash? Would mixing half tank of e10 and half tank of e85 screw with the computers, being it's not strictly 1 or the other (e10 or e85)?

I read the post above stating he tried e85, lost his mpg, now with e10 his mpg is lower than before intrducing e85. That concerns me, as I want to experiment, but don't want to mess anything up. I understand I'm going to drop to about 12 to 13 mpg jn e85, but once I run e10 again, I dont want it to drop below what I currently get for mpg (18 roughly avg city & highway combined).

Any imput would be great!

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#27 spankrz

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Posted 30 September 2011 - 12:57 AM

Could this explain why I can't get any better than 16 MPG out of my 07 Avalanche? I never leave the key on but I may have driven less than 7 miles after adding E85 to a tank with E10 in it. I have been disappointed in the MPG of this truck from day one. Hell, my 04 Av got better mileage than this one. I am the same person doing the same job and driving the same places with the same driving habits. I typically got 16 out of the 04. This new truck typically gets 13. I recently took a 400 mile road trip on nothing but 70 MPH Hwy. I reset the computer at the start of the trip and after that trip I had averaged 16 MPG.

I have a friend with an 07 Av and he always averages better than 16 MPG. He has never put E85 in his truck. His is 4WD mine is 2WD. I know driving habits play a big part but no matter I drive I can't get better than 16.

TIA,
Matt


you are getting worse mileage because it takes twice as much alcohol to do the same thing as gas (or about). you are going from 10 percent alcohol to 85 percent alcohol. the engine has to burn massive amounts of the e85 compared to e10 in order to acheive the same results. that is why the pcm has to relearn the fuel. it knows how much more to shoot to it.
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#28 spankrz

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Posted 30 September 2011 - 01:03 AM

My truck had recently had trouble with hard starts while cold and running rich codes. Took it into the dealer and the tech told me that the computer was expecting fuel with a higher alcohol content than was in my tank ( I only use ethanol free ESSO fuel). The dealer fixed it under warranty.


ethanol free fuel???? where and how??? i would kill to get my hands on that.... i am a small engine mechanic. if you think ethanol sucks in your truck, try it in a small engine which fuel mixture is controlled by a rubber gasket that hardens over the winter if you leave gas in it :lol:
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"you can live in your truck, but you can't drive a house"
07 nnbs silverado ext cab 4x4, 2" rc level, 285/70r17 maxxis bighorns, 20% tint, flowmaster 40 series muffler with factory pipes, airaid MIT tube, spectre drop-in filter. 150,000 miles and still going strong.

#29 yamahas

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Posted 10 November 2011 - 09:09 PM

My truck had recently had trouble with hard starts while cold and running rich codes. Took it into the dealer and the tech told me that the computer was expecting fuel with a higher alcohol content than was in my tank ( I only use ethanol free ESSO fuel). The dealer fixed it under warranty.


ethanol free fuel???? where and how??? i would kill to get my hands on that.... i am a small engine mechanic. if you think ethanol sucks in your truck, try it in a small engine which fuel mixture is controlled by a rubber gasket that hardens over the winter if you leave gas in it :freak:



Check this out, my buddy's like to use gas stations in the lists when they fill their 2 strokes.

http://www.pure-gas.org/

#30 fred walters

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Posted 19 February 2012 - 10:29 AM

I have a 2011 GMC Sierra 5.3 V8 Flex fuel. Bought in 12/2010. Just put in first tank ( 20 gallons) of flex fuel. About 70 cents cheaper than tier one fuel in the metro NY area.. Milage dropped from about 14.5 to a little under 12.0 around town. Will this get better or is this about an average drop in mpg's. Do not think I am really saving much $.




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