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Old 02-27-2012, 06:27 AM   #46
ARG OP
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Joel,

Thanks for the reply on retrofitting. Sounds like I will be dumping the 09 and getting a newer one after I look in the tank to verify a float. That way I will also get the new vented differential. Don't know which farkles will transfer from an 09 to an 11 or 12 so will sell the 09 while it is still bone stock.
Thanks for the info,

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Old 02-28-2012, 01:21 PM   #47
JohnnieWinona
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09GSa

30k, i went through 3 in the first 12 months. i thought all was well, as the 3rd has lasted more then a year...until last month, on a trip to CA, it went flueee, but different then the other bad strips. It reads fine until 1/2 or so, then begins a downward pace quickly until it reads '-- miles left' on the fuel range. In reality i have anywhere from 200miles left, to 50miles left. This is a problem, as i use it a lot, i'm in the out back. i'm thinking about adding some SeaFoam, as it has worked with assorted other motors with various aliments. my service guy said they have not made any changes that he knows of.
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Old 02-28-2012, 03:59 PM   #48
JoelWisman
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Seafoam, Techron, STP, XYZ....... None make the slightest difference, ever.

There was an early theory postulated by a BMW USA FSE that crud could be building up on the strip causing inaccuracy, But none of the other FSE's nor I ever thought that theory held any water and testing as well as looking at the condition of failed fuel strips showed that theory to NOT be the case.


Here is what a fuel strip is and how it works:

A long thin strip of plastic has two circuits printed onto it. One circuit is carbon and forms a 3 sided box down, across, and back up the strip. This is the heater circuit.

A second circuit that zigzags down, across and back up is printed inside the 3 sided box formed by the heater circuit. This circuit is printed out of something that changes resistance greatly with temperature.

Wires are soldered to the pads near the top of the strip.

Next another long thin strip of plastic is placed over the strip thats printed, and the two are heat laminated together. This forms a liquid tight assembly, including the pads where the wires are soldered.

All told, the strip is about as thick as two pieces of paper and just as flexible.

Next the strip is placed inside two pieces of rigid black plastic that is snapped together. The plastic holds the strip by the edge, is hollow in the center, has slits to allow fuel to flow around the strip, and is shaped.

ONTO HOW IT WORKS:

Once every 90 seconds, the bike sends current to the heater circuit of the strip. The portion of the strip that is above the fuel heats to about 100 F above ambient. This also heats the sensor circuit which changes resistance with temperature. The computer then reads the resistance of the sensor circuit, and from the reading, knows how much of the strip is above the fuel level of the tank, and hence, what the fuel level is.

Fuel splashes around the tank so the computer waits till a couple of 90 second cycles have passed, takes the average, then updates the fuel level read-out. This is why it takes a while to update the gauge after you fuel up.

Conversely, if you start the bike but don't move it at all, the computer sees the resistance of the sensor circuit is stable and updates within 90 seconds.


HOW BMW's STRIPS ARE BREAKING:

I tested about 30 failed BMW fuel strips, some with my doubting FSE present (If you ever read this, you know I love you Mike) Without exception, in every case the sensor circuit trace broke inside the strip. There was never a failure of the strip to be water tight so no contamination. Nothing was ever built up on the outside of the strip, the solder pads were never bad.

The strip has to have low thermal mass to react the same month to fuel levels, hence it has to be thin and flexible. The rigid plastic snapped over it has to be open to good fuel flow, and fuel sloshing around the strip is going to flex it.

The heater printing material is carbon and very flexible. Whatever the sensor circuit is printed out of, evidentially it is not flexible.

WHY MANUFACTURES CHOOSE FUEL STRIPS:

1: Mainly, they are cheap, real cheap. When I worked for Volvo corporate we tested out fuel strips for a year. The cost of a custom made fuel strip at the quantity we would have bought them was about $4.35 apiece :)

I immagine BMW pays more. There is an economy to scale and to put the manufactures size difference in perspective, Volvo could have bought BMW Motorrad by writing a check out of it's operating account without tapping into it's capitol investment account. BMW likely pays 2 or 3 times this amount, but it's still cheap.

2: you can make the strip and it's rigid support any shape you want, so you can run it from top to bottom in an odd shaped tank. BMW certainly has some odd shaped tanks and floats that have to go up and down in an arc can't measure the full spectrum of full to empty in odd shaped tanks. This is why on nearly all BMW's that have floats, the fuel reading shows full till you burn half a tank, then start reading accurately.

A typical mediocre quality float will cost a manufacture $20-30 bucks apiece. The floats BMW is using in their bikes is mediocre at best, and sorry to say, having plenty of reliability problems though an order of magnitude fewer then the strips.

These look just like a toilet tank float. There is a rigid circuit board near the float hinge and a sliding contact attached to the float arm near the hinge that rides the circuit trace on the board.

The trace on the board is resistive, and depending on where the sliding contact is positioned, changes resistance.

Failures of this style of fuel sensor come in 4 flavors.

1: the trace is worn off of the board. I haven't seen this occur with any of the new floats, yet.

2: The circuit is contaminated with junk from the fuel and develops dead sections where fuel level readings will go from full to empty then back to whatever the level really is once the float lowers past the dead spot. I have seen this quite a bit. Chevron or BMW Techron WILL help prevent this.

3: Ethanol contaminated with water corrodes the circuit board and makes its readings totally unreliable. It may show full when its empty, empty when it's full, anything in-between or even show fuel level increasing as it's actually falling. I have seen the new floats do this, BMW or Chevron Techron will also help prevent this.

4: The keeper washer on the float arm falls off. I have seen this a few times lol, picked the washer out of the fuel strainer, bent it so that it will stay on better, and sent the bike down the road with everybody happy till warranty refused to pay my labor since I didn't replace the part :jerk

So, floats costs more, still fail but not as often, and can't read the top half of oddly shaped tanks like the F800GS and R1200GS/GSA have.


TO BMW MOTORRAD GERMANY:

There is a third common style of fuel level sensor (Volvo has been using them since the early 90's) This sensor uses a rod with a zig-zagging wire inside of it. Its completely sealed in ridged plastic so no contamination or flexing cracks. You put a doughnut shaped float around it that rides up and down the rod. The doughnut contains a magnet. Depending on where the float is floating, the magnet changes the capacitance of the circuit inside the rod, and the rod needn't be straight. You can curve it gently to follow the contour of an odd shape tank.

No circuits exposed to fuel, all are encased.

No sliding electrical traces to wear out.

Nothing flexes so no cracked circuits.

The worst thing that can happen is so much crud builds up on the rod that it blocks the float. Easy to fix, just take a screwdriver and knock the slag off. In any case, fuel this bad would have killed about a dozen of BMW's crap Bosch fuel pumps so techs would notice this build-up long before the float couldn't ride over it.

The only draw back, it's the most expensive system. Volvo pays about $48 bucks apiece, and BMW with small production runs would pay more.

But hey, no more boards filled with BMW fuel gauge woes, near zero warranty costs, and the system is super accurate and completely unaffected by wear induced inaccuracy so BMW, you can roll out a "miles to empty" feature that is actually accurate and dependable.

I will offer my services on behalf of BMW on negotiating a good price and the USA parts boss can vouch personally for me. I know all the names in parts production except for Bosch which always pissed me off.

A case of french wine, german chocolate, ski trip to swiss alps, all expenses paid and a very young high class french escort and I will lock in the same rate Volvo pays.

P.S. I want the chocolate but the escort and everything else is for the parts rep. Also depending on the supplier, we may have to find a male escort, but I digress.



Lastly, you can fix the broken strips to work as good or better then new in about 2 minutes without removing it from the tank.

BMW just ask your parts boss how. I showed him in person, and the strip I fixed was still working a year and a half later, as were several others I did this 2 minute fix on.

It's worth exploring because the 10 and earlier bikes with strips are going to haunt you for a long time and expecting the owners to buy newer bikes if they want reliable fuel gauges isn't polite.
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Old 02-28-2012, 04:12 PM   #49
marty hill
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Joel, I've not had any fuel strip problems but would like to thank you for your insight and willingness to put in on paper.
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Old 02-28-2012, 04:23 PM   #50
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Well written Joel
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Old 02-28-2012, 04:37 PM   #51
JohnnieWinona
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i took Joel's advice and removed the neck, which also included removeing some of the shrouds on the top of the tank. As i was pokin'round i saw that the right fuel-line had come unclipped from the tank fitting. How i don't know --unless it was not installed correctly. But, i refitted it, and all is working again. Yeah. So it was not the fuel strip, but a fuel pick-up. Thank you Joel for getting me to look a bit closer.
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Old 02-28-2012, 04:44 PM   #52
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Lastly, you can fix the broken strips to work as good or better then new in about 2 minutes without removing it from the tank.

BMW just ask your parts boss how. I showed him in person, and the strip I fixed was still working a year and a half later, as were several others I did this 2 minute fix on.

So when are you going to tell us civilians how to do it
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Old 02-28-2012, 04:49 PM   #53
JohnnieWinona
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Joel, thank you for the explaination, what and how, in simple, understandable, elegant terms. i'll take the escort/wine.
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Old 02-28-2012, 05:02 PM   #54
ARG OP
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Joel,

I would love your letter to get to Motorcycle Consumer News in response to the original letter that I sent to them. Thanks for your valuable information.

ARG
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Old 02-28-2012, 05:38 PM   #55
Dorian
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Quote:
Originally Posted by JoelWisman View Post
Lastly, you can fix the broken strips to work as good or better then new in about 2 minutes without removing it from the tank.

BMW just ask your parts boss how. I showed him in person, and the strip I fixed was still working a year and a half later, as were several others I did this 2 minute fix on.

It's worth exploring because the 10 and earlier bikes with strips are going to haunt you for a long time and expecting the owners to buy newer bikes if they want reliable fuel gauges isn't polite.
Yes thanks heaps for the explanation! Is there a secret handshake/password involved in finding out how to fix the broken strips?
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Old 02-28-2012, 05:42 PM   #56
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1: Thank you everyone. I spend time writing what I write because I love the adventure community I am a part of. Knowing that the information is helpful to others makes it more then worth it.

2: The quick fix requires some equipment. Basically, you shock the thing back to life. The printed sensor circuit is super fine and completely laminated between layers of plastic. Hit it with a high voltage with a little capacitive current behind it, and it repairs it.

I discovered this on accident while using a magger to test out why the strips Volvo was testing were failing.

I don't know if the current welds the broken trace back together, the arc at the break creates a carbon trace that conducts across the break, or it fixes it for some other reason that hasn't occurred to me, but it works, about 100% of the time once you get the joules right.

For the BMW strips, I used a 50 pF capacitor across my test leads on a Fluke 1520 megger for a power source. Set the merger to 1000 volts, charge up your 1000 volt or better 50 pF capacitor and hit it across the sensor circuit of the strip, capacitor and megger still connected, megger still powering. For gods sake, detach the connector on the strip from the bikes computer!!!!!

The megger is high voltage but very low current, which is what you want. The capacitor gives it a brief current kick.

In any case, not only does it fix the strips, but with both the Volvo and BMW strips, it not only fixes them but once the current is just right, makes them more reliable.

I only tested this on 3 BMW's with broken strips, but when last I was working at a BMW dealership, all 3 were still working and 2 were going on 2 years in service.

If doing this with the strip still in the tank, it would be safest for the tank to be full, but not only is it unlikely a strip would ever be in such a state that the arc would occur outside the strip, but in almost all conceivable conditions, the vapors in the tank would be way to rich to support combustion, otherwise the brushes on the fuel pump would cause excitement regularly.

That said, I defer to anyone thinking of trying this to use their own judgment on the safety of this procedure and hold me blameless should they blow themselves up

3: I detest many bike journalist because they oh so eloquently write so much while imparting so very little actual information. MCN is an exception. I love the MCN guys and they are free to use anything I write on adventure rider without royalty, attributed or not. Heck, for the joy of a 10 minute conversation with them I will write anything I know (things about which I signed a non-disclosure form excepted) that they desire.
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Old 02-29-2012, 06:34 PM   #57
PanhandleChuck
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Fuel strip replaced by BMW Motorrad of Pensacola yesterday. Fault warning was fuel strip. So, at 18K on 2010 GSA, fuel strip one replaced!
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Old 03-01-2012, 04:40 AM   #58
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3rd time the charm?

I need to make an appointment to get mine in for another replacement. This will be the third strip since August of last year. 2009 1200GS, 11,000 miles. Not good...
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Old 03-01-2012, 05:03 AM   #59
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Originally Posted by maineiac-moto View Post
I need to make an appointment to get mine in for another replacement. This will be the third strip since August of last year. 2009 1200GS, 11,000 miles. Not good...
There is no charm. Keep replacing or ignore it and use the trip meter, unfortunately.
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Old 03-01-2012, 05:09 AM   #60
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And I'm fine with simply using the trip meter. I just wish they would come up remedy so I don't have to keep seeing the fault light and low fuel warning flashing at me. That would be a more acceptable fix for me than to keep replacing a defective part.
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