lost the gas gauge again

[BailyD]

The two bikes were delivered in 2007....gauge broke three days later. It was fixed and subsequently broke broke between every service...(+) up to 22,000 miles. This department bike's gas gauage was fixed at the 19,000 mile service and now it's broken at 22,000 AGAIN.

 

My partners gauge just went out too! I think my total is about 5 times since 2007.

[JayW]

I wonder if the real problem with these repeatedly failing fuel strips is actually an electrical problem further "upstream", perhaps similar in causality to why some bikes blow headlight bulbs every few months, while the next guy's bike still sports the original ones from the factory. Maybe the strips are getting "burned out" through no fault of their own.

 

Plausible?

 

Jay

[ccii42104]

I have an 09 and am on my third strip. Frustrating considering my 07 GT had 46k on it when i sold it and never had a problem. Wierd. I basically just refuel every 200 miles now like i do with my KLR!

[Hall Vince]

I wonder if the real problem with these repeatedly failing fuel strips is actually an electrical problem further "upstream", perhaps similar in causality to why some bikes blow headlight bulbs every few months, while the next guy's bike still sports the original ones from the factory. Maybe the strips are getting "burned out" through no fault of their own.

 

Plausible?

 

Jay

 

I think it's plausable.

M RT eats low beam bulbs almost as much as I eat chocolate and the OE fuel strip is still working fine at 31,000 miles as was the strip in my 05 R12st at 33,000.

 

I wonder if it's a fuel thing.

 

It's interesting that some rider get repeated failures, 2 or more on same bike so perhaps the fuel being used locally is the culpret.

 

I wonder if it's possible that a fuel additive in some companies fuel is attacking the strip.

On the flip side I fill up whenever I need fuel. My preferance is branded companies like BP or Shell, but if I'm empty I fill up where ever.

 

The only thing I would say is my bikeis rarely left stood for more than two days. Exception being Christmas when it can be stood for a week or two.

 

Other than that it's used daily, filled up to top, trip reset, when the light comes on and countdown is near 0 or within 20 miles depending how near I am to fuel sation I fill up to brim again.

 

I wonder if there is any correlation between riders who may only add a few liters in a splash an dash or owners who leave bike for extended periods full or empty of fuel?

 

many questions, many answers, I'm off to fill up with fuel, hope I've not put a hex on the strip now!

\v/

[EddyQ]

I wonder if the real problem with these repeatedly failing fuel strips is actually an electrical problem further "upstream", perhaps similar in causality to why some bikes blow headlight bulbs every few months, while the next guy's bike still sports the original ones from the factory. Maybe the strips are getting "burned out" through no fault of their own.

 

Plausible?

 

Absolutely plausible. I often wonder the same thing.

Let's see.

1) We loose headlights which could be vibration, but over voltage could also be a cause.

2) We have fuel pump controllers, which could be water/corrosion related (but there are folks that say the failed controller is dry with no corrosion). Overvoltage would likely kill it quick.

3) Antenna ring. Another electronic device which high voltage could effect if not understood.

4) Fuel strips. Resistive strip in the tank. Usually, a resistor will fail due to heat or mechanical movements effecting connection.

I would guess overvoltage would need to be quite severe and carry a lot of energy. Less plausible, but I don't know much about the circuit that connects to this strip.

 

Sure, the system runs on a 12Vdc battery which likely increases to 14Vdc when engine is running. But short duration transients often exist on car and bike systems. How big and long the transient is and how it occurs and handled is a mystery.

 

Often, high energy voltage transients get generated where high power devices are turned on and off. The high power device surges high current on the wires, connectors all the way from the battery positive terminal and back to the battery negative terminal. Current surges will cause voltages (which normally are zero) across finite wire impedances, connector contacts and at the switch that switches on and off. Often, power wires (especially ground wires) are shared with low power circuits. That is often how a high voltage transient will couple and kill low power circuits.

 

When switching high power, it is best to switch such that the current gradually increases or decreases. This is almost never the case. A mechanical switch will abruptly make connection at microsecond speeds. An electronic device such as those used in the ZFE can be designed to switch with low transients, but at the cost of consuming higher power and bigger size (so they likely switch as fast as possible, which likely is faster than the mechanical switch).

 

It would be very interesting to connect an digital oscilloscope with differencial probes to the headlamp, fuel pump controller and fuel strip and capture long events of starting and running the bike. If you see a large long duration transient, maybe it can be traced to something that we can fix. But that would be quite an effort.

[dirtrider]

I wonder if the real problem with these repeatedly failing fuel strips is actually an electrical problem further "upstream", perhaps similar in causality to why some bikes blow headlight bulbs every few months, while the next guy's bike still sports the original ones from the factory. Maybe the strips are getting "burned out" through no fault of their own.

 

Plausible?

 

Jay

 

Hi Jay

 

There is definitely something going on with those fuel strips. I just had the 6th one installed.

 

Real difficult to believe it is farther “upstream” as nothing ever needs to be replace in that area. A simple new strip install and the gauge works just fine again. If it was farther upstream the new strip wouldn’t work correctly after install or the removed strip would have an open from over current or over voltage.

 

In fact I have a bunch of failed strips on my test bench here and both the sensor fuel level resistor and strip heating resistor ohm out OK compared to a new unmolested strip. So that tells me no stray voltage is damaging the strip. Plus if it were just a simple stray voltage or stray current issue BMW would have a permanent fix by now as a well placed clamping resistor or such would handle that. BMW “or their suppliers” are paying out a fortune to replace these fuel strips so you know they are diligently working on viable fix.

 

These things are a vinyl type of material with embedded resistor material so you would think that fuel additives wouldn’t be able to effect the strip surface itself. Even if fuel additives or sulfur compounds could effect the strip resistance you would think I could measure that in my static resistance measurements.

 

So that pretty well points to something else that is effecting the strip functionality. This I can’t tell you at the moment but the strip electrical connector is not a sealed connector so I suppose it is possible that fuel additives or sulfur type compounds are effecting the terminal resistance or allowing cross talk between the heating circuit and fuel level resistor circuit or allowing cross talk between the fuel pump electrics and the sensor circuit.

The junction on the top of the fuel strip between the strip resistors and it’s remote wire harness pigtail looks somewhat sealed but the attachment area is encased in a hard epoxy like material so my guess would be that this the weak spot in the present fuel strip. Even if it were sealed completely, with that remote plug end being inside the fuel tank and unsealed I suppose it would be possible for the fuel to wick down the stranded wires inside the insulation and down into that sealed connection area.

If the problem was caused by either electrical leakage or added resistance at the top of the strip itself that would explain why I haven’t been able to statically measure the strip resistance and pick out a failed strip over a good strip. If it were a fuel additive or sulfur related resistance issue I would have to do my resistance measuring with the strip still in the tank and being wet with fuel so that path was still active.

 

I might be getting a little closer to the root but am still just guessing on this. My newly replaced fuel strips seem to work fairly accurately for a while just riding locally. But riding locally I usually just fill the tank to the bottom of the fill ring. I usually get the strip to start acting up after a long trip as on those I usually stuff the tank as full as possible sometimes the day before trip then on the length of the trip do the same by basically overfilling the tank. At one time I though filling the tank from the off-side was a contributor but am having second thoughts about that as every time I have filled from the right-hand side I have always also stuffed the tank completely full to the very top. One thing that overfilling does is place that strip to wire pigtail junction at the top of the fuel strip completely under fuel.

 

You know darn well that BMW and their fuel strip supplier are working at 100% trying to figure this thing out as it is presently costing them big money to keep replacing those fuel strips. They "BMW" are presently not requesting the BMW dealers to send the failed strips back to BMW on warranty replacements so they either know what the root cause is and are working on a new and improved or have enough in their hands to not need any more. On the same note if BMW engineering had any thought at all that the problem was farther upstream they would be requesting replacement of the upstream parts with the old remove parts being captured for dissection and failure analysis.

 

[BailyD]

what happens when the warranty expires in a few months? Shouldn't they be accountable for a fuel gauge that hasn't lasted more than a few thousand miles after each new one is put in?

[dirtrider]

Hi Baily

 

BMW gives you 2 years warranty on all parts installed so you get 2 years from the day your last fuel gauge strip was installed. Moral here is to get a new fuel strip just before your factory warranty runs out.

 

[JayW]

Well dirtrider, you seem to know as much or more about these strips as anyone I have heard of who is not affiliated with BMW. So if I understand, you are saying that if they were burning out like a light bulb from a power surge or some such, then there would be an open circuit in the strip that you could locate as evidence of such. Makes sense.

 

It still seems odd to me that the problem seemingly cannot be permanently fixed on some bikes, whereas others, like mine, have never had a fuel strip problem even after 5+ years and many many fill ups. I routinely fill my tank up to the tippity top, unless I am about done riding for the day.

 

Thanks for your detailed and thoughtful response. There has gotta be a better answer than to just replacing strip after strip after strip.....on the same bike. I suppose there could be some batch-to-batch variations in manufacturing that causes some strips to be more likely to fail than others, but that would mean quite a few owners have really bad luck.

 

 

Jay

[EddyQ]

Interesting data dirtrider.

 

I'm not sure exactly how this thing works, but here goes:

The ZFE likely puts a fixed current to the resistive strip. The portion of the strip that is outside the gas warms and changes resistance. This produces a different voltage at the ZFE and therefor gas level can be predicted. Now, strip to strip, tank to tank and maybe ZFE to ZFE have variations very significant so the "system" needs calibration.

 

Is it possible that a bad strip is nothing more than a shift of resistance? Based on the range of resistances specified in some tech manual the strip is good. But to a calibrated system, it moved a huge amount.

 

I disagree with your statement that something upstream wouldn't cause damage because the system is good after strip replacement.

That's like saying a 5amp fuse cannot damage a bulb downstream without blowing.

 

I wouldn't bet BMW knows what is going on. They might be working hard to figure it out. They thought they had the fuel pump controller figured out when the gave us an improved circuit. That seems to have issues too.

[dirtrider]

Evening Jay

 

It would be interesting to import your bike to my area and see if you then get a gauge failure.

Do you know of any gas gauge failures in your area? I know of quite a few in and around my area. If not many failures in your area it could be fuel or weather related.

 

Those fuel strips have more than a few places they could fail. The first is the sensor resistor along the length of the strip, the second is the heating resistor along the length of the strip, the third is extra resistance in any of the connections or wires to or from the strip, the fourth is electrical bridging at any of the connections, or on the strip itself, then you have other possibilities like fuel conductivity, possible sulfur buildup, maybe high water content in alcohol containing fuel, maybe something none of us have through of yet.

 

It would be nice if BMW or BMWs supplier could get a handle on this and get some sort of permanent fix. On the K bike some are going back to a float type unit, rumor has it that maybe the GS will go that way in the future.

I’m sure nobody would like this problem to go away more than BMW.

 

[dirtrider]

High Eddy

 

You are close on the operation. The ZFE heats the strip and the fuel cools the strip at and below current fuel level but the resistance change is measured on a separate parallel resistor to the heater resistor.

 

The thing is, if the ZFE or other upstream electrical component damaged the resistive strip it would show in the resistive measurement comparing a new unmolested strip and a number of failed strips. But what I haven’t done “yet” is do any wet resistance tests.

There “seems to be” a resistance issue here somewhere but so far it “seems” external to the film area on the strip.

 

BMW does have a service test to remove the strip, dry it “I believe overnight”, then recalibrate the dry strip, then add fuel and re-test the gauge operation. I doubt many BMW dealers actually do this as it is very time and work space consuming so the easy way out is to just install and calibrate a new fuel strip.

 

I wish the GS-911 had a fuel strip calibration function as I would like to clean up then try and re-use some of those failed fuel strips I have. My current feeling is they would work just fine “again” for a while.

One thing I do notice when measuring the old strip resistance is it is very difficult to get a repetitive resistance measurement until I clean the terminals on the pigtail plug. Now this might mean something then again some of these strips have been sitting around a while before I got them so maybe just old fuel residue or alcohol induced oxidation after removal then exposure to the ambient air.

 

You better believe both BMW engineering and the specific strip supplier is working diligently to resolve this gauge issue as it is costing both of them an awful lot of money. Now that’s not saying any new “improved” strips aren’t going first into new builds rather than as replacement stock.

I guess we’ll know more when we see what type of gauging units the 2011 RTs and GSs come with in early production.

Problem is, even if they go back to a float on a resistive pot. there are a lot of newer automobiles that are having similar issues with fuel related contamination on the fuel gauge sender so that just might bring on different gauge malfunction issues.

 

This wouldn’t be such a big issue if BMW could find a way to install a manual reserve on an electric fuel pump equipped fuel injected vehicle. Most of us have ridden motorcycles for years that didn’t have fuel gauges but they did have KNOWN quantity manual position reserves.

 

[JayW]

Evening Jay

It would be interesting to import your bike to my area and see if you then get a gauge failure.

 

Maybe, but the riding area might be a more important indicator. I have purchased at least several tanks of gas in Ohio, and have also filled up in about 35 other states. For science, I could take my strip out, send it to you for installation in your bike and we could see what happens.

 

 

 

Nah.

 

Jay

[dirtrider]

For science, I could take my strip out, send it to you for installation in your bike and we could see what happens.

 

 

 

 

 

Jay

 

Morning Jay

 

That wouldn’t help as I have no way to calibrate the darn thing after the swap out. If I could use the GS-911 to calibrate I could also try some of the strips that I have that ohm out correctly.

 

[pdes]

 

You know darn well that BMW and their fuel strip supplier are working at 100% trying to figure this thing out as it is presently costing them big money to keep replacing those fuel strips.

Are you sure? I used to think like this but the proportion of strips failing outside warranty must be significantly higher than those under warranty - therefore, the repairs could be quite a money spinner for their dealerships. Call me cynical but I do not believe that BMW with their vast resources couldn't fix this in very short order if they wanted to. I understand that they are thinking of re-introducing a mechanical float next year but if they were serious about sorting this, they could easily have developed a retro-fit mechanical alternative for current bikes. I remain thoroughly disgusted at BMW's complacent attitude to those of us who have coughed-up for a top-of-the-range product. (Still love the bike though!)