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Old 03-17-2012, 04:03 PM   #121
drmajor
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Faulty Fuel; LS

wow, I would be happy to have a full reading all the time. If all I need is a simple resistor in the between 2-3 that's a piece of cake. What OHMS? Does the wattage matter?

I was reading on the UK GS [UKGSer.com ] sight and they quite a list of failures. BMW should be nicer about fixing this...... Maybe next bike needs to be the Tiger or V-Strom- 40% less cash on the Strom.
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Old 03-17-2012, 11:47 PM   #122
JoelWisman
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Quote:
Originally Posted by Old_Don View Post
Joel,

I happen to have a new strip in my garage. Pins 1 - 4 is 32 Ohm. I believe that's the heater circuit. My RT feeds it with 9 Vdc at key on and after ~ 5 sec. it drops to 7.5 Vdc.

Pins 2 - 3 have 2.4k Ohms across them.

My old strip ( still in the bike) has an open across pins 2 - 3 and the gauge reads empty. I'll swap it out one of these days. :-)

Thank You for all of your posts on this topic.
Thats it then, thanks :)

On your old bike, the receptacle on the top of the fuel pump access does have 4 wires, yes? and it is the center two that are open, i.e. to the strip sensor circuit?

2,400 ohms is in the ball park, but different years were different, some are higher. I used to have all these specs at my finger tips, but now I have to pester someone at a dealer, same as everyone else. I will rattle one of my sources cages again and try to post the specs.

I would think a 1/4 watt resistor would do it, but without measuring sensor current, I'm not certain, probably best safe, use a 1 watt resistor.
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Old 03-18-2012, 12:57 AM   #123
TXjames
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Quote:
Originally Posted by Old_Don View Post
Joel,

I happen to have a new strip in my garage. Pins 1 - 4 is 32 Ohm. I believe that's the heater circuit. My RT feeds it with 9 Vdc at key on and after ~ 5 sec. it drops to 7.5 Vdc.

Pins 2 - 3 have 2.4k Ohms across them.

My old strip ( still in the bike) has an open across pins 2 - 3 and the gauge reads empty. I'll swap it out one of these days. :-)

Thank You for all of your posts on this topic.
Excellent post Don! Thanks for the info. I'll compare your results with my own and post up when I return home.

A couple of thoughts on your findings...

EDIT: THIS IS MY INCORRECT INTERPRETATION OF STRIP OPERATION. SEE JOEL'S RESPONSE BELOW

1. Your 2400 ohms is with the strip out of the tank. So that would be an empty reading. I would think there should be much less resistance when in a full tank.

2. The dealer calibration may play a factor in the actual fuel level reading. I'm guessing the calibration measures the strip's resistance at full and empty and then stores those values in the ECU as max and min. Therefore, readings from your new strip or someone else's on this thread may not equate to a full tank on another bike. This really doesn't matter since the goal is to not have a constant low fuel light or worse, error code. It's just a thought in case someone is trying to achieve a full tank.

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Old 03-18-2012, 01:31 AM   #124
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Originally Posted by TXjames View Post
Excellent post Don! Thanks for the info. I'll compare your results with my own and post up when I return home.

A couple of thoughts on your findings...

1. Your 2400 ohms is with the strip out of the tank. So that would be an empty reading. I would think there should be much less resistance when in a full tank.

2. The dealer calibration may play a factor in the actual fuel level reading. I'm guessing the calibration measures the strip's resistance at full and empty and then stores those values in the ECU as max and min. Therefore, readings from your new strip or someone else's on this thread may not equate to a full tank on another bike. This really doesn't matter since the goal is to not have a constant low fuel light or worse, error code. It's just a thought in case someone is trying to achieve a full tank.
Thats not how it works. The 2,400 ohms is the tank FULL reading because the strip is all at room temperature.

When the strip is in the bike, a current is applied to pins 1 and 4 which heats the strip. The portion of the strip that is above fuel level warms greatly which changes the resistance to a higher value.

The portion of the strip that is immersed in fuel does not appreciably change temperature because the fuel wicks away the small heating produced in the strip.


For calibration, the MOSS is attached to the bike, and the completely dry strip is attached to the bikes connector while the strip is outside of the fuel tank.

The bike reads the "un-heated" resistance of the strip and records that as "tank full", then heats the strip and records the higher heated resistance as "tank empty".

A dry unheated strip will have the same resistance as a strip fully immersed in gas with heating current flowing, so all wee need to do is plug in a resistance that equals a dry strip (possibly a little lower, strips do vary some), leave the heater plugged in, and I think we have it.
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Old 03-18-2012, 09:46 AM   #125
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Quote:
Originally Posted by JoelWisman View Post
Thats not how it works. The 2,400 ohms is the tank FULL reading because the strip is all at room temperature.

When the strip is in the bike, a current is applied to pins 1 and 4 which heats the strip. The portion of the strip that is above fuel level warms greatly which changes the resistance to a higher value.

The portion of the strip that is immersed in fuel does not appreciably change temperature because the fuel wicks away the small heating produced in the strip.


For calibration, the MOSS is attached to the bike, and the completely dry strip is attached to the bikes connector while the strip is outside of the fuel tank.

The bike reads the "un-heated" resistance of the strip and records that as "tank full", then heats the strip and records the higher heated resistance as "tank empty".

A dry unheated strip will have the same resistance as a strip fully immersed in gas with heating current flowing, so all wee need to do is plug in a resistance that equals a dry strip (possibly a little lower, strips do vary some), leave the heater plugged in, and I think we have it.
Thanks for setting me straight Joel. I posted an edit in my post so as not to misinform. So the fuel level and the resistance of the strip are inversely related? That makes Don's measurements of an uninstalled strip all the more valuable.

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Old 03-18-2012, 12:01 PM   #126
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Ok, I measured a strip off an '05 Rt that I have parts for.

1-4 = 35.8 ohms
2-3 = 2475 ohms
measured at 60 degF
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Old 03-18-2012, 05:58 PM   #127
Old_Don
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Quote:
Originally Posted by JoelWisman View Post
Thats it then, thanks :)

On your old bike, the receptacle on the top of the fuel pump access does have 4 wires, yes? and it is the center two that are open, i.e. to the strip sensor circuit?
Yes 4 wires and the center two (pins 2 & 3) are open.
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Old 03-18-2012, 06:30 PM   #128
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Quote:
Originally Posted by JoelWisman View Post
Thats not how it works. The 2,400 ohms is the tank FULL reading because the strip is all at room temperature.

When the strip is in the bike, a current is applied to pins 1 and 4 which heats the strip. The portion of the strip that is above fuel level warms greatly which changes the resistance to a higher value.

The portion of the strip that is immersed in fuel does not appreciably change temperature because the fuel wicks away the small heating produced in the strip.


For calibration, the MOSS is attached to the bike, and the completely dry strip is attached to the bikes connector while the strip is outside of the fuel tank.

The bike reads the "un-heated" resistance of the strip and records that as "tank full", then heats the strip and records the higher heated resistance as "tank empty".

A dry unheated strip will have the same resistance as a strip fully immersed in gas with heating current flowing, so all wee need to do is plug in a resistance that equals a dry strip (possibly a little lower, strips do vary some), leave the heater plugged in, and I think we have it.
Okay, that's why the tank level reading didn't change when I LOWERED the resistance. I went the wrong way!!! I'll try a higher resistance tomorrow and play around with the value. Thanks Joel!
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Old 03-18-2012, 08:03 PM   #129
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Get one of these pots and fine tune your resistance.
One day you can pretend you have a full tank, next day 1/2 tank.
Endless amounts of fun !!

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Old 03-19-2012, 10:07 PM   #130
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I connected up the 10k potentiometer and tried all values from zero to 10k. Bike always showed the fault
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Old 03-19-2012, 11:29 PM   #131
JoelWisman
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Quote:
Originally Posted by TrollGSA View Post
I connected up the 10k potentiometer and tried all values from zero to 10k. Bike always showed the fault
The heater needs to remain plugged in and the resistance needs to equal precisely full take before the bike is switched on. any other resistance and it will post a code
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Old 03-20-2012, 07:07 AM   #132
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Originally Posted by JoelWisman View Post
The heater needs to remain plugged in and the resistance needs to equal precisely full take before the bike is switched on. any other resistance and it will post a code
WTF was BMW thinking? All of this complexity and fault checking for a fuel level indicator that, even when working, is insanely inaccurate. It's not like we're on a mission to Mars.

This is a textbook example of over-engineering.
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Old 03-20-2012, 09:16 AM   #133
qman8
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Originally Posted by davegaz View Post
WTF was BMW thinking? All of this complexity and fault checking for a fuel level indicator that, even when working, is insanely inaccurate. It's not like we're on a mission to Mars.

This is a textbook example of over-engineering.

Are you new to BMW? This is Standard Operating Procedure for BMW! Its a Tuetonic thing!
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Old 03-22-2012, 10:24 AM   #134
TXjames
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What are the odds?

Unbelievable! Washed my bike last night with the intention of checking the strip resistance today. Fired it up for a ride after the wash and... FUEL warning flashing! WTF. This strip was replaced by the dealer in March 2011! Surely not...

Surely so! I tested the strip and heater: pins1-4 are 34 ohms and 2-3 open. Gonna cut the wires for 2-3 and solder them to a pot to see if I can make the Endless Tank Trick work today. If so, I'll replace it with a resistor for permanent installation.
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Old 03-22-2012, 10:52 AM   #135
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Soldered in a pot set to 2420 ohms, replacing the strip. Computer is still flashing the warning indicator and not reading fuel level. Is this a latching alarm that needs to be cleared with GS-911 or have I not fixed the problem?
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