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Crossing fuel gauge wires?


RoSPA_man

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I don't think anyone knows for sure exactly how it is intended to work outside of BMW's engineering dept. but there is no end to speculation in countless threads in just about every BMW forum so take your pick. Regardless, we now know how to make the gauge read anything we want so it wouldn't be all that difficult to design an interface between the combi display and any fuel sensor you could come up with, permitting an aftermarket replacement of the trouble-prone stock system. But I'm not sure why it would be worth the effort as a simple trip odometer works better as a fuel gauge than just about anything else anyway.

 

Well done Smiller and James and everyone else for running this to a full solution.

 

Based on James's advice, I simply put the tiny 2K resistor across 2&3 and spliced the nearby accessory socket for a +12v feed via the tiny 1M resistor. I taped it all up and it is so neat now - a full tank and no warning lights! My only fear now is that an indicated full tank always may make me blasé and I may forget to check the all-important odometer! Even the tape that blocked out the warning light used to be a reminder! This was excellent collaboration to achieve a great result.

 

 

 

 

 

Edited by RoSPA_man
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And thanks for being so observant Hugh as your hint provided the key. Once you have something working in some configuration then it's easy to work it back, but getting to that point can be difficult. I'm not sure when (or if) it would have been figured out without your critically important clue.

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Just a thought, normally these strips work without need of an external supply, so would it work if a feed was taken from Pin 1 or 2 (depending on which is Positive +) to supply the 1M resistor, maybe a small resistor would be needed as I’ve read the voltage on the heater circuit varies between 9v-7.5v, maybe 700k, but i'm just guessing.

This may be worth looking into for a cleaner installation. Then a jumper to 12V wouldn't be necessary. BTW, the source should be either pin 1 or 4. That's the heater circuit.

 

I'd think if the circuit does need a very small bias, this should work.

 

However, it does make me wonder why this circuit needs this bias when it didn't with the original circuit.

I know resistance measurements were made between the heater ciruit and found no connection, but now that we see 1Mohm is all that it takes, are we still sure there is no high resistance connection?

 

My RT strip is working and I am tempted to head out an make voltage measurements on all four pins to chassis ground. My DVM has a much higher resistance than 1Mohm. I think it is >100Mohm, so it will not upset the ciruit.

 

I agree with all here Huge. Great discovery.

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CLEANER INSTALLATION OPTION:

 

Easter Sunday afforded me some time to play with the cleaner installation that was discussed in previous threads. Long story short, it turns out that the heater circuit is a good voltage source for the strip circuit. So no need to run a 12V jumper anymore. This configuration prevents the microscopic battery drainage that would be present in the first version of The Infinite Tank (as though it were something to worry about) and, more importantly, saves time in configuring the fuel strip spoof. All work can now be done at the four pin connector.

 

The heater circuit only provides 10.3V and it does so intermittently; cycling on for 12 seconds and then dropping to 1V for 30 seconds. I thought this may pose a problem but apparently the ZFE also samples the strip circuit simultaneously... as might be suspected. I know because it works!

 

So here's the new and improved strip spoofing circuit:

 

FuelStripSpoof_v2.jpg

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CLEANER INSTALLATION OPTION:

 

Easter Sunday afforded me some time to play with the cleaner installation that was discussed in previous threads. Long story short, it turns out that the heater circuit is a good voltage source for the strip circuit. So no need to run a 12V jumper anymore. This configuration prevents the microscopic battery drainage that would be present in the first version of The Infinite Tank (as though it were something to worry about) and, more importantly, saves time in configuring the fuel strip spoof. All work can now be done at the four pin connector.

 

The heater circuit only provides 10.3V and it does so intermittently; cycling on for 12 seconds and then dropping to 1V for 30 seconds. I thought this may pose a problem but apparently the ZFE also samples the strip circuit simultaneously... as might be suspected. I know because it works!

 

So here's the new and improved strip spoofing circuit:

 

FuelStripSpoof_v2.jpg

 

A thing of beauty is a joy forever - that's neat!

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Perhaps it's the EE in me, but I dislike making wiring changes, especially providing power to circuits that shouldn't require it, when I don't know how the circuits work in the first place. I hope someone doesn't wind up having to replace their ZFE.

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Perhaps it's the EE in me, but I dislike making wiring changes, especially providing power to circuits that shouldn't require it, when I don't know how the circuits work in the first place. I hope someone doesn't wind up having to replace their ZFE.

The current flow is tiny, very unlikely to damage anything. But if concerned one always has the option of continuing to replace fuel strips.

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How may watt (rated) are the resistors your using?

 

tiny: eighth watt. Not a lot of current flowing through these circuits. Particularly the 1M resistor.

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The resistors are installed instead of the fuel strip (i.e. remains disconnected) or in addtion to a in place connected but misbehaving strip?

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The resistors are installed instead of the fuel strip (i.e. remains disconnected) or in addtion to a in place connected but misbehaving strip?

Just as in the circuit diagram, i.e. pins 2 & 3 are isolated from the fuel strip and 1 & 4 are left connected. Pins 1 & 4 are the heater circuit and if that is left open then it will set a code and light the warning triangle.

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Now that we have the elegant "2 resistor in the connector" method to disable the fuel strip preventing the engine from being shut down while on the interstate in rush hour traffic, I wonder if we could disable the heater element.

 

While nobody here knows the failure mode, it is plausible, even likely, that removing the heat cycles (12 seconds on / 30 seconds off) will prevent or extend the life of a fuel strip so that it could be reconnected in the future, should one desire.

 

Given that an open circuit generates a fault, a resistor could be installed in place of the heater element (indeed it is a heater element!). Besides possibly extending the life of the not being use fuel strip, this would allow the connector to remain disconnected from the fuel strip and the complete solution embedded in a dead end connector plugged in to the wiring harness. Or, if, or should I say when, a fuel strip fails on the road, it could be disconnected and this plug installed to get you going.

 

I am not in a position to measure the current draw or voltage drop of the heater element (during its 12 second on period), but if someone could do that we would know the value and power (size) of the resistor. It would most likely be fairly low given that I suspect it just measures the rate of resistance change during the 12 second heat up period. But it is a heater. We just need enough current draw to keep the fault detection off.

 

--Gerry

 

 

 

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Now that we have the elegant "2 resistor in the connector" method to disable the fuel strip preventing the engine from being shut down while on the interstate in rush hour traffic, I wonder if we could disable the heater element.

 

Gerry,

 

I'm not sure I understand your comment about preventing the engine from being shut down. Could you elaborate?

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It is my understanding, from reports here, that one of the failure modes of the fuel strip, besides an incorrect quantity, is that the engine is shut down and a tow is required. There was one in Germany and at least one in the US, if I recall correctly.

 

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It is my understanding, from reports here, that one of the failure modes of the fuel strip, besides an incorrect quantity, is that the engine is shut down and a tow is required. There was one in Germany and at least one in the US, if I recall correctly.

 

 

 

Afternoon boat-pilot

 

That is an incorrect understanding. The only way a defective fuel gauge will shut down a BMW 1200RT is IF you run it out of fuel due to the faulty gauge.

 

Otherwise all you get is the fuel gauge not functioning & possibly the low fuel light always on.

 

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I hope you're correct and I'm wrong - that it's only a soft failure. I was going by posts such as this one on BMW MOA:

 

The strip failed on my 2010 R1200R twice in the first 1000 miles. The first time it failed with a full indication. The second time it left me stranded in the middle of an intersection. The bike acted just like it was out of fuel, even though I only had about 150 miles on a full tank. There was still plenty of fuel sloshing around in there. the GS-911 indicated a pump failure and it could not be reset. I had to be towed. After verifying no failure in the fuel pump, the dealer replaced the strip and the problem cleared. Be aware- these repeated failures are not simply about not knowing how much fuel is in the tank. It can leave you stranded.

__________________

patrick

'10 r1200r

...and some benzes

 

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Evening boat-pilot

 

Something crossed up with his understanding of the failure.

 

Again, a failed fuel strip can't & won't cause the bike to quit running. It's just a simple gauge that quit working. Now if you run it out of fuel that is a different story.

 

Look at it common sense wise-- Common sense says why would any motor company have their bike quit running if the gas gauge malfunctions? What would be the reason or the gain?

 

My guess is that person had a FPC (fuel pump controller) fail & cause his bike to stop running. The dealer probably put in a new FPC as well as a fuel strip.

 

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You could probably use a resistor in place of the heating element, although rough calculations show that it would need to dissipate about a watt or so you'd need to use an appropriately-rated part. The low duty cycle would help.

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Nice n Easy Rider
I hope you're correct and I'm wrong - that it's only a soft failure. I was going by posts such as this one on BMW MOA:

 

The strip failed on my 2010 R1200R twice in the first 1000 miles. The first time it failed with a full indication. The second time it left me stranded in the middle of an intersection. The bike acted just like it was out of fuel, even though I only had about 150 miles on a full tank. There was still plenty of fuel sloshing around in there. the GS-911 indicated a pump failure and it could not be reset. I had to be towed. After verifying no failure in the fuel pump, the dealer replaced the strip and the problem cleared. Be aware- these repeated failures are not simply about not knowing how much fuel is in the tank. It can leave you stranded.

__________________

patrick

'10 r1200r

...and some benzes

 

I'm on my third strip. The first time it failed the engine stopped (because I was out of fuel). The second time the only problem was the yellow light staying on. I don't think there is any connection between the strip and the engine. :D

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  • 2 weeks later...

A couple of questions concerning resistor fix?

Will just installing the resistor clear the fault and make the tank appear to have fuel without any other action?

Will starting the bike with the sensor unplugged create a fault that has to be cleared externally (GS-911)?

Has anybody got this to work on a 2010 model?

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Will just installing the resistor clear the fault and make the tank appear to have fuel without any other action?

Will starting the bike with the sensor unplugged create a fault that has to be cleared externally (GS-911)?

Has anybody got this to work on a 2010 model?

Once the resistor mod is done all external alarms will disappear (no need to manually clear) and the gauge will permanently read full. After initial installation it may take 30-60 seconds for the warning light to clear, then it won't be back. The mod is new so hasn't been tested on all years and models equipped with a fuel strip. I would expect it to work for all (although possibly the low-value resistor may need to be tweaked), we'll see. And of course this is not meant for any newer bikes equipped with a float sensor.

 

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I'd really like to get rid of that annoying low fuel warning, and have a never ending supply of gas.

A little confused: should I pull the plug to the fuel strip, and insert the resisters into the male end, leaving the plug un-plugged? or do I have to cut & solder the resisters into the harness, and leave it plugged into the fuel strip?

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looks like cut, solder in those resistors.. then plug it back together... You need pins 1 and 4 connected across the strip heater..

 

 

Edited by w2ge
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I'd really like to get rid of that annoying low fuel warning, and have a never ending supply of gas.

A little confused: should I pull the plug to the fuel strip, and insert the resisters into the male end, leaving the plug un-plugged? or do I have to cut & solder the resisters into the harness, and leave it plugged into the fuel strip?

 

Yes, you must replace the strip on pins two and three with a resistor and tap pin four for the voltage source. Pins one and four must remain connected so that the absence of the heater won't throw a code.

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Be aware- these repeated failures are not simply about not knowing how much fuel is in the tank. It can leave you stranded.

 

Excuse me Patrick but this is not the case. If anyone questions whether or not the strip can leave them stranded, just unplug the four pin connector and run the bike. You will see the only thing to worry about is the yellow flashing triangle distracting you from the road.

Edited by Jameseo
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If DR says the fuel strip failure and the engine quitting (due to that) isn't related.. then it isn't related! He is "THE ORACLE"!

 

...and so shall it be written! ;-)

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In doing this on a 2008RT tonight, it wouldn't work. Undid it, redid it, no luck.

 

While removing everything to return it to stock I undid the connection to the Red/Green. For giggles I turned the key on and full tank, no flashy yellow or gas pump symbol.

 

I was using what I had around, 2x1k, and 1 by 1M resistors. So what I ended up with, in series, 1M,1K, and 1K resistors from the Gr/Br to the Brown/blue, The Red green was not connected.

 

The bike starts and runs as normal. (with no flashy lights!!)

 

Thanks gents!

 

 

 

FuelStripSpoof_v2.jpg

Edited by Nesbocaj
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In doing this on a 2008RT tonight, it wouldn't work. Undid it, redid it, no luck.

 

While removing everything to return it to stock I undid the connection to the Red/Green. For giggles I turned the key on and full tank, no flashy yellow or gas pump symbol.

 

I was using what I had around, 2x1k, and 1 by 1M resistors. So what I ended up with, in series, 1M,1K, and 1K resistors from the Gr/Br to the Brown/blue, The Red green was not connected.

 

 

Dang, that lasted about 20 miles, then back to the yellow triangle.

Back home, undone, back to stock for now.

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  • 1 month later...
Perhaps it's the EE in me, but I dislike making wiring changes, especially providing power to circuits that shouldn't require it, when I don't know how the circuits work in the first place. I hope someone doesn't wind up having to replace their ZFE.

 

Still going, some 5K miles later!

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erikrichard
THIS JUST IN...

 

Bill the Bong on ADV was told by his dealer that " BMW has developed new software to drive the fuel strips". Don't know which dealer that is or if the statement is true but it's certainly something everyone should consider and be on the lookout for. I may have to call my dealer and inquire...

 

After reading a bunch about this, the computer software has nothing to do with anything, the connection in the strip is breaking. Why BMW's supplier has been unable to make a more robust strip is very puzzling indeed...

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  • 1 month later...
After reading a bunch about this, the computer software has nothing to do with anything, the connection in the strip is breaking. Why BMW's supplier has been unable to make a more robust strip is very puzzling indeed...

My understanding as far as I have read is that the junction where the wires connect to the resistive coating and the heater are under a layer of epoxy which nobody has been able to remove yet, to see the internals.

As such it is not at all clear that the failure is mechanical and not electrical.

If the voltage/current is driven by the computer (as we can see at the heater element's ON/OFF cycle) and lets assume it is an actual electrical failure, then it very well could be fixed via software by changing the duty cycle and possibly the voltage (if the voltage can be varied via the software and isn't a constant).

 

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  • 6 months later...

Th fuel strip on my 2009 RT is so far still working, but just to get ready for a potential failure - could somebody point me to location of this connector discussed in this thread?

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I undid the connection to the Red/Green...

 

The Red green was not connected.

FuelStripSpoof_v2.jpg

 

 

Yes. This is why I did not connect pins 2 (brown/violet) and 3 (green/red) on the drawing. The 2k resistor replaces the fuel strip. But I will modify it to more clearly show the disconnect.

Edited by Jameseo
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Th fuel strip on my 2009 RT is so far still working, but just to get ready for a potential failure - could somebody point me to location of this connector discussed in this thread?

 

It's the 4-pin connector going to the fuel tank on the fuel pump (left) side of the tank. NOT the one going to the regulator.

 

The one in the background here...

GSFuelPump.jpg

Edited by Jameseo
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Thanks for the pics Jameseo and dirtrider. I think next to it is the fuel pump controller, and that was one of the things I wanted to check out when I do my next service.

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  • 2 weeks later...

Don't know how I missed this thread until now... since it's been awhile since you guys came up with this, is it still a trouble free solution to at least get rid of the warning light?

 

How about either marketing it to us less mechanically inclined, or how about a step by step tutorial with parts numbers / supplier so we can make one too.

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Don't know how I missed this thread until now... since it's been awhile since you guys came up with this, is it still a trouble free solution to at least get rid of the warning light?

 

How about either marketing it to us less mechanically inclined, or how about a step by step tutorial with parts numbers / supplier so we can make one too.

 

As of now, this required cutting into the harness and soldering in the correct resistances. I would love to create a plug and play solution but haven't located the tank side connector.

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  • 3 months later...
CoolHand1969
Don't know how I missed this thread until now... since it's been awhile since you guys came up with this, is it still a trouble free solution to at least get rid of the warning light?

 

How about either marketing it to us less mechanically inclined, or how about a step by step tutorial with parts numbers / supplier so we can make one too.

 

As of now, this required cutting into the harness and soldering in the correct resistances. I would love to create a plug and play solution but haven't located the tank side connector.

 

I just implemented this and didn't cut into the harness, although it's a bit hokey and I wouldn't be surprised if something works loose sometime.. I did it all with 14 gauge butt splices basically. I crimped the ends of two down a bit so they'd be tight, and slid them over the outer pins of the fuel strip connector. then coming out of the pin one butt splice, I ran a wire up to the harness connector (of appropriate guage to be somewhat tight going into the harness connector). Coming out of pin 4 I ran a small wire to another butt splice, which on the opposite side had the 1M resistor as well as another wire crimped into it (which went to the harness connector). Then off the 1M resistor I had it butt spliced to a 2.2k resistor (couldn't find a 2.0k in my kit for some reason) as well as a wire to the harness connector. Then off the backside of the 2.2k resistor butt splice was one more wire to the harness connector. Apply electrical tape liberally where necessary.... It's made it a hundred miles so far.. :) The tank shows just above empty - I'm guessing because I used the 2.2k instead of 2.0k... I actually like that better than full, because if I glance at it, it mentally prompts me to check my odometer instead of subconciously having the security of a "full" tank...

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  • 4 months later...

Hello, I wanted to thank you because thanks to you, I could always have a gauge to max . I made a change. As my gauge is broken, I replaced the heating part by a resistor 39 ohm 1Watt. It works fine. This allows me to not have the Fuel Tank Gauge.

Now, if you did not put your gauge in the trash, then you can save it. Here is the link that explains how.

http://www.advrider.com/forums/showpost.php?p=21268240&postcount=253

Thank you.

Mpapy8, French has the same gauge problems in France ....

Edited by Le Francais
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Le Francais...

 

That "fix" has had somewhat limited success... Some died within days...

 

I have been following the whole thread. Its about 90% good. some have to be "re flashed" and work, only a few don't.

 

Just count the number of times it worked and didn't.

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^Yes, and to be honest I would certainly give it a try myself. Nothing to lose...

 

Knock on wood, mine has been.... (2010, 18K+ miles)

 

(Don't even want to type it out as I don't want to jinx myself, but you know what I mean! ;-)

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The fuel gauge on my new 2013 R1200R never worked from day one. The local shop had replaced the fuel strip 4 or 5 times. Finally, my fuel strip was just replaced with a new part number (as of a few days ago) and it's still working after about 5 tankfuls. It did act a little strange when I got down to less than a gallon of fuel - it suddenly showed empty. After the next fill-up, it worked properly again.

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When I bought my 2012 R1200R, Driving it home I thought "Hey they filled the tank for me". I rode about 70 miles and filled it agian. It took 4 gallons. It holds 4.8 + 3 quart reserve. After that it worked better but died around 20,000 miles. It was replaced with a new one and works better than ever. I would depend on it if I didn't hang around here. :grin:

 

Sacken, what was the part # of the new strip?

 

Been using the trip meter on everything I own all my life.

 

David

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For what it's worth, my latest fuel strip has lasted longer than any other (& still working); I've noticed something interesting which may or may not have any bearing on longevity.

 

My fuel guage shows full until I've used up about 3 gallons of petro, then drops to the correct level all at once. I gladly accept this if it would mean a long lasting fuel strip. Knowing nothing about electronics, I'm wondering if this strip has a thicker sensor in the area prone to failure.

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