Topsy Turvy Fuel Reading

[websterize]

Why does my fuel gauge keep lying to me?

After filling up tonight, the low-fuel lamp illuminated, and there were zero bars in the fuel-capacity on the multifunction display. Before filling up all the fuel-capacity bars showed full, and the low-fuel warning lamp was dark. I filled up with four gallons of 93.

Looks as if the fuel strip needs to be recalibrated — and maybe replaced? Is this something that can only be done with a near-empty tank?

As many have said here, the trip odometer is our friend. Reset it after every fill up.

[Meatloaf]

Why does my fuel gauge keep lying to me?

The fuel sensor on mine had to be replaced before I took delivery from the show room floor.

[websterize]

Clearly this is a problem with 2009 white models.

So the fuel readings get weirder. Riding to work this morning the range readout of the trip computer counted down from 230 miles to "---" in all of about 20 minutes, like it was a countdown timer. My inbound commute is 10 miles.

[websterize]

There's interesting discussion about faulty hexhead fuel gauges in this thread at BMW MOA; a 2008 K1200S rider is on his fourth fuel-sensor strip.

edit: and here, too: viewtopic.php?f=20&t=14888&p=132476&hil ... or#p132476

I suspect my bike's problem is with this strip, which is No. 8 below:



Apparently, the fuel sensor works by changing resistance depending on which part of the strip is being heated. How much the sensor is submerged in fuel affects resistance.

[MIKE46]

Forget the number of bars left showing, forget the readout for mileage left - fill up when your trip mileometer shows that you have done about 190 miles, you will still have nearly a gallon left so will never run out! That is my experience in the 23.000 miles that I have done in the last three years on my 1200R.

[xprof]

Me, I expect to fill at about 230 miles. Never had a problem with that.

[websterize]

Forget the number of bars left showing, forget the readout for mileage left - fill up when your trip mileometer shows that you have done about 190 miles, you will still have nearly a gallon left so will never run out!

Agreed, but it's difficult to ignore the low-fuel lamp with a full tank of gas. That's why I will request a fix.

[websterize]

Had the "fuel level sender" replaced today. The tech "drained the fuel tank, tried to recalibrate the strip, renewed the film strip and reprogrammed the strip after installation." He put my fuel back in the tank — even topped it off — and everything appeared okay after service: no low-fuel lamp on a full tank, and residual-range display counted down as it used to.

The job took two hours and was covered under warranty.

[websterize]

An interesting line in the product description of BMW fuel system cleaner (PN 82140413341) for sale at sierrabmwonline.com:

- Regular use of BMW Group Fuel System Cleaner Plus can prevent fuel gauge malfunction caused by harmful sulfur components found in some fuels.

I use high-octane and try to buy only from the big fuel companies. Who knows? BMW recommends using the fuel cleaner every 3,000 miles.

[Mollygrubber]

Hmmm. I bet BMW branded fuel system cleaner is 2 to 3 times more expensive than everthing else.

Not that a few dollars is going to kill anyone, but what the hell.

I wonder if NOT using it will give you warranty headaches...?

Seems to be made by Chevron, and is available w/o the BMW branding & additional cost.

Check out this thread, it's been discussed at length here.

http://www.xoutpost.com/bmw-sav-forums/ ... chron.html

[deilenberger]

I doubt if sulphur deposits have any relation to our fuel-sensor problems. There are problems with some of the resistive sensors used on BMW cars.. had it on my '99 M-Coupe, replaced with an updated one. The avoidance for problems with these ones was periodic use of Techron (or re-branded Techron from BMW.)

The strip sensor we have should be immune to this sort of problem. The one we have is an updated version of the ones used on the '84-85 K bikes, which worked even worse. They use a strip resistor (long ribbon) that has a current flowing through it to heat it up. The amount of current going through it is what is read for fuel-level. The difference in heat-transfer from air to gasoline is what varies the current, and as fuel level drops - the amount of current needed to heat it up drops. It's a wonderful idea that works well in the lab, but as BMW proved once on the K bikes, not so good on the road. If I had to point at anything that might cause damage to it - it would be ethanol in the fuel - probably attacking the material the resistive strip is embedded in and allowing short circuits to occur. On the '85 K bikes there were only 2 discrete resistors - one for first yellow light warning at one level, one below it for the red light warning. Had one - my yellow light was always on, and the red light just randomly flickered. Worthless and I eventually removed the bulbs and went to a FuelPlus+.

That's what BMW should be using. It's a simpler device, but you have to remember to reset it when you fuel up. It actually measures the amount of fuel used by watching the injector frequency and pulse length (on-cycle) and calculating that against the miles you've travelled since the last fill-up. Works very well - could be user calibrated for larger tanks, and is now probably worth more used than it was new since the chap who made it stopped making the simple K bike model.

With all the data on the CANBUS BMW could do this sort of design, but I'm betting they don't want to count on the owners resetting the device every time they got gas - so they went to one that measures the level in the tank.

Anyway - the point of this long digression - fuel cleaner is unlikely to make any difference in the longevity of our fuel sensors. Using fuel without ethanol, or fuel where the quantity of ethanol is tightly controlled so it doesn't exceed 10% is probably a better idea. Buying cheap fuel.. well.. sometimes you get what you pay for.

[deilenberger]

BTW - if anyone gets their sensor replaced outside warranty - ask for the old one. I'd love to dissect one and see if I can figure out what is going wrong with them..

[Kieran R1200R]

At least you got one. I didn't want ESA, and wanted a white bike. Eventually they found one, but it came with TC and tyre monitering. On the display there's gear selection, tyre monitoring, distance, no fuel and no temp!! Work that one out!

[websterize]

At least you got one. I didn't want ESA, and wanted a white bike. Eventually they found one, but it came with TC and tyre monitering. On the display there's gear selection, tyre monitoring, distance, no fuel and no temp!! Work that one out!

Sounds as if, in addition to the ESA option, your bike is also missing the On Board Computer option (code 539). If I had to choose one, I'd probably have gone for the ASC and TPM, too. OBC is nice but not as mission critical (to this rider) as the stability control and tire-pressure monitoring safety options.

And who can pass up Alpine White?

[Kieran R1200R]

I would have liked the onboard computer, but more importantly at least temp meter.
Down here in Australia the market for anything is so small compared to you guys in America we are lucky even to have one. I'll give you some idea. Last year BMW Aus, sold 1,100 units all up, that's every model.
So when they put an order in for bikes they usually ask for fully optioned, so we get little choice. I came across the R12R as a loan bike, putting my R12S in for a service. I had it for a day and at the end was asking myself why I didn't have one. I mean it was that much better I just wanted it. It didn't have ESA and it handled really good. I road a RT with ESA and it is good on that bike, but for me on the R12R is would have been a waste because this bike likes to turn so much why not give it a helping hand and put Ohlins on it, which I did and now it is supurb! I new I wanted White and no ESA so I was lucky to get what I got. Is there an option for me to at least get a temp gauge in the instrument diplay?

[Mollygrubber]

Not likely from BMW, but there are oil temp. gauges you can find aftermarket...