WTF is up with the fuel range on my '09 F800GS?

Discussion in 'Parallel Universe' started by (I^2)R/746, Apr 5, 2015.

  1. (I^2)R/746

    (I^2)R/746 Rider

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    Okay so I have a new to me 2009 F800GS I've put about 1500 miles on and it has just under 10k total miles on it. As I figure out the bike fuel range is a big item to get nailed down. So here's an interesting experience I had the other day when on a weekend trip riding 2-up:
    1) Average mileage indicator says I'm getting 43mpg I've reset this about 600 miles ago should be fairly accurate. Yes I know that's kind of low.
    2) I reset my "A" trip meter every tank. I'm out larking around and the trip meter says 170 miles. Should be about out of gas, right? 4.2 gallon tank, right? Sure but the little reserve indicator says I have between 40 and 60 miles left (changes a bit) so I keep going for a bit. At this point I'm going light on the throttle and heading for gas....
    3) Around every RIGHT hand corner the bike sputters like it's running out of fuel. Not on the straights, not on the left corner, just on the right corner. The sharper the right the worse it is. Sputters then recovers like it's running out of gas. At this point I'm kind of worried. Right before town there's a real sharp like 10mph right hand corner and the bike flat out dies. Get off the road crank for 20 seconds kind of die. Bike starts back up.
    4) Get to gas station put in 3.66 gallons fuel. Full up. Thought the tank was 4.2 gal? And at 43mpg how the hell did it only use 3.66 and get me 170+ miles?

    So I'm confused. Funky BMW electronics not to be trusted? I'm thinking a couple Rotopax, one on each side of my top case, are in my near future. Anybody have any enlightenment about this?

    Not that it matters but bike has K60 tires, BMW AF-XiED and Remus header with stock can. I don't expect great mileage with that setup, especially 2-up, but would like to be told the truth... or plan around the lie. Whatever. TIA.
    #1
  2. Saltboxlad

    Saltboxlad Long timer

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    All I can say is that you are getting about what I would expect MPG wise, when my fuel light comes on and the count-down starts If I go straight into a fuel station I normally get about 13 Litres in (3.5 US Galls). According to the specs reserve should be about 2.7 to 3 litres (0.7 US Galls). What I have no idea about is why your bike should be having trouble getting the last reserve amount of fuel, unless you are getting an air lock, did you hear a rush of air when you opened the fuel cap?
    #2
    OneEyedJack likes this.
  3. (I^2)R/746

    (I^2)R/746 Rider

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    Right! So the first sign of this was straight up and down at low speed it just died and then restarted. I pulled over and started looking at stuff. Opened the gas cap and it made a "whuff" sound. So I think "Aha! I've found it!" and start tracing lines out. Figured I had a pinched line somewhere. I had previously done a canisterectomy on it and run the line straight from the vent down to between the swingarm and the engine. Maybe it had hit the exhaust and seared closed? No dice the line was fine. Blew through it with the gas cap open vents fine. It was after that the problems really showed up.... this dying around right hand corners only. Got to the gas station and no pressure when opening the gas cap. 3.66 gallons all it took. Got back to my friends house, took out my GS-911, and read the system with my phone. Only error showed up was standing fault for air purge valve which is correct as I removed it along with the canister. How the heck would that make a difference?

    At this point ready to remove fuel pump assembly and start looking around. I want to be able to run that thing dry!
    #3
  4. Indy Unlimited

    Indy Unlimited Long timer

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    I have pulled up to the gas pump after doing 238 miles and filled her with 4.2 US gallons twice now. So I know the tank is correct. Your fuel pump can be oriented and the pick up point adjusted. The round top plate on top may be slightly out of position and you will need to pull the unit out to see which position allows for the best pick up and mark the angle on top and place down then lock with the ring nut.
    I also have never had sputtering with a half gallon left so I suspect your fuel pump pick up is not at the bottom.
    #4
  5. Reaver

    Reaver Why am I still here?

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    The trip computer is an educated guess. If you rely on that absolutely then you'll be pushing it often. The miles remaining changes drastically if the load changes like going up a hill or hitting the highway. I don't know if it's able to take an aftermarket enricher into account.

    The fuel pickup has no choice where to be as everything's keyed into place. It sits in the bottom of the tank, lowest part so I can't guess why a rh turn affects it while a left wouldn't also.

    Running the fuel low regularly shortens the pump's life as it prefers to be immersed in fuel for cooling, so the owners in the hot places say. Sounds like you need a Camel tank. :D
    #5
  6. Bayner

    Bayner Long timer

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    The pump inlet filter can fall off pretty easily. You might want to check that as well.
    I've found my distance to empty readings to be quite accurate. As I understand it the calculations do not reset when you clear the average speed and mileage data from the display. Having said that I still trust my trip meter over all else.
    I agree with Reaver that pumps do not like to be run dry. Try to avoid that when possible.
    #6
  7. Rgconner

    Rgconner Long timer

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    They should be very accurate, given that the computer knows exactly how much fuel was delivered, the EFI delivers exactly the same amount of fuel every time it is triggered, and how fast the bike is going.

    Aftermarket enricher would not matter unless it bypasses the EFI somehow.
    #7
  8. Reaver

    Reaver Why am I still here?

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    The fuel level is a guess, based on a float and resistance. It wears out and can be inaccurate. I'm going to guess the DTE will take the enricher's effect into account since the ECU just thinks it's cold outside, but BMW and it's programming aren't necessarily logical.

    Basically, if the trip computer thinks it has x units of fuel left, but the actual amount as reported by a mechanical sender which averages out a sloshing tank has a, say 10% error, then it may go to -25 kms to empty as on my bike. That's 25 kms after I'm supposed to be out and one run-on sentence. The computer then rethinks things so the next time it'll be different.

    It's not an absolute gauge. Ride accordingly.


    If you want an adventure, run out of gas. :D
    #8
  9. Reaver

    Reaver Why am I still here?

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    ......and all the early fuel senders were recalled. Check your '09.
    #9
  10. Hamish71

    Hamish71 Been here awhile

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    I have a MY13 and I have ONCE had a similar issue.
    On the highway, knew of a stop upo the road, but when I go there it has closed down. 35km to the next fuel and the light was already on. I reckon I had done about 35 km on the light whn it started to sputter....it would run fine, then sputter, then go again. No turning or whatever involved, I was on the freeway.

    I got to the next stop, filled it up, no problem since. Definitely something to do with the pick up.
    #10
  11. CheckerdD

    CheckerdD Long timer

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    My fuel economy and fill amounts do vary. But I don't think twice about it as long as it seems to average in the mid 40's. The biggest variances were riding across Russia last summer with some other BMW riders - sometimes in the low 30's and high 60's. A Russian motorcyclist explained that in Russia the states don't certify how accurate the gas pumps are at stations. Dave
    #11
  12. PFFOG

    PFFOG Richard Alps-aholic Supporter

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    Pull the pump, something amiss in the PU. I have put over 4 gallons in several times, well on the far side of 220 miles.

    I average aver 55, flogging the crap out of it on back roads. Cruising at 65-70 yields worse mileage. Riding when the wife is following on back roads pushed 70mpg a couple times.
    #12
  13. MTrider16

    MTrider16 Ridin' in MT

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    +1 on Reaver fuel sensor recall. I always go by the trip meter, never the calculated mpg, so I can't say how well they compare. I haven't heard anyone talk about the right hand turn problem you describe so maybe a fuel pump or filter is possible, not sure.

    Here is a copy of the fuel and mileage datasheet from my ride to Alaska.

    Mileage at fill is from the trip meter. Highlighted cells are stops I used fuel from my spare tanks.

    [​IMG]
    #13
  14. Mr B

    Mr B Been here awhile

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    Just to muddy the water a bit, I tried to run out of gas once, with a two liters spare on board I wanted to see how many miles a tank could produce.( I am getting about 48 to 49 miles per gallon on average.) '09 with about 21,000 miles on the clock..
    anyway I get the low fuel light and the countdown begins. About 15 miles to town I hit "O" miles till empty...then the DTE goes " - - - ". I proceed to town and put in a splash more then 4.1 gallons. I clocked about 221 miles.
    I came to the logical conclusion not to trust the DTE and simple reset the trip meter ever fill up. Start looking for gas at about 170 miles or so...
    As for the sputtering, I put in a new Fuel Pump from these guys, mine was stalling every now and again...

    http://www.highflowfuel.com/i-8927843-new-intank-efi-fuel-pump-bmw-f800gs-f800gt-2006-2014.html

    Simple install and my stalling issues have disappeared.

    good luck
    :1drink
    #14
  15. (I^2)R/746

    (I^2)R/746 Rider

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    Wow! Thanks for all the responses! I quickly pulled the pump and found the fuel pickup screen had fallen off. That said I'm not convinced that little thing is worth 1/2 gallon of unusable fuel and comments here make me think something on my bike isn't quite right. I agree running the pump dry is a bad idea but I think more research, with a one gallon Rotopax on board, is warranted. I'm bugged a bit by the mileage indicators (both average and remaining) and will stay old school with the trip meter.

    I did NOT see any particular way to adjust the pump pickup orientation or depth. Did I miss something?

    Fuel light? What fuel light? Keep in mind I really just got the bike so I have no idea. But one did not come on at all. Perhaps because I had 1/2 gallon left when I was running out? I just had the little countdown thing which, depending on how I was on the throttle, would indicate 40 to 60 miles (me thinking like 20 maybe was safe). A fuel light would be nice.....

    I did call BMW about recalls open/done on the bike after purchase. There were none open I was told. I will look into the fuel sender and see what is what. I think I am on my own. Third owner of an '09 with 8200 miles.

    As for mileage I think I'm getting average. I live in the coastal mountains and they are well... mountainous. All my vehicles get poor mileage, poor tire wear and are hard on brakes. My work truck costs a bundle to keep in shape!

    Sigh. This bike. 70 miles after I got it the rear wheel bearings blew up and stranded me. A few hundred miles later I notice the valve cover is seeping. I installed the pipe, fuel controller, AK-20 in the front, BDCW skid plate, Madstad screen, Clearwater Krista and am waiting on my Yacugar shock to come in. I'm looking forward to getting this all shaken down and fixed the way I like it so I can get about those camping trips I have planned. I'll have to camp as I won't be able to afford hotels due to fixing the bike up. Oh well such is life.

    Going to continue tests and if I can't get all the fuel in that tank I'm going to find a way to make a custom pickup hose with a weight. I have some BMW fuel hose around from working on my '02 R1150GS that should do the trick. If that turns out to be the fix I'll post up pics for your amusement.
    #15
  16. itsatdm

    itsatdm Long timer

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    My bike is similar to yours, in that its the same year and similar mods. I also live in the mountains.

    Our year bikes have a different fuel gauge than later models. Ours measures miles to empty from fill up. Initially it will show a number and an arrow sign indicating more than what's indicated to empty. At about 40 miles to empty the fuel light comes on. It is not that accurate until that happens.

    Even then on mine, I will have up to a 1/2 gal left when it indicates empty. At least it is consistant. On the current tank, the electronic mileage indicator states average mileage at 56mpg, I have 195 miles on the tank with 20mile to empty. Your mileage doesn't sound that good unless you have the normal luggage, windscreen mods and doing a lot of Freeway with the AF Xied set at a rich mixture.

    The electronic mileage indicator has been pretty accurate. Anywhere from 54 to 62 mpg, if I keep it under 65 and it depends on what altitude I have been riding at. At freeway speeds I lost a couple of MPG with the AFXied (43-46). I have owned this bike since 9/2008, my current AF Xied is set at 14.2 AFR, with a temp spoofer and the bike has been geared up. I have over 5,000+ miles on it with different AFR and gearing. It hasn't made much difference on mileage from stock.


    I don't know what is wrong with your bike, but BMW changed the design of the fuel gauge because it was so inaccurate and they got tired of doing warranty work. I suspect a fuel pump issue, but Reaver is a better gauge than me.
    #16
  17. (I^2)R/746

    (I^2)R/746 Rider

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    Thanks this is exactly the kind of information I was looking for when I posted my issue! Now I know I need to keep looking instead of chalking it up to "they all do that". If there's a fuel pump issue I want it to fail NOW when I'm close to home.

    My mileage around home has been about 43 and the AF-XiED didn't seem to affect anything but add smoothness and a bit of power. I ran about 500 miles stock then put the AF-XiED on at the "8" setting and the Remus header pipe at the same time. About 800 miles since same fuel economy indicated. This with just a topcase. I just installed a larger windscreen we shall see what effect that has.

    The more I think about it the more it's possible this an an early indication of fuel pump failure. If the pump relies on being immersed to stay cool enough to operate it stands to reason symptoms may begin to show up only under near empty tank conditions where the heat sink is substantially less. It's possible the pump may be vapor locking at is gets towards empty and doing this as the gas, the heatsink, sloshes towards the minimum immersion point (even though there is fuel left). Hence the right hand turn only symptom. I'll be doing some thread searching here for fuel pump replacement.

    Thanks everybody this place is pretty awesome.
    #17