Fuel Strip Failure - interesting thread..

[deilenberger]

If you're out of your fuel strip warranty - this is something to consider - the always full fuel tank:

http://bmwsporttouring.com/ubbthreads/u ... 624&page=6

The thread is interesting.. the value for the heater strip is the same as I measured on a dead one someone sent me.. and as they found - the sensing part of the strip appears to be open on them when they fail. Also interesting that a power source is needed for the sensing strip, even though a working one doesn't provide it.

[Bob Ain't Stoppin']

Don, I read the page 6&7 of the linked thread. They talk about a heater strip. What are we heating? Is this the low fuel lamp? It would be nice if we could keep the low fuel lamp when bypassing the strip. I don't know what triggers the lamp though. Do you know?

[MTBeemer]

Sooner or later someone will produce a plug-in device as mentioned. Electrical stuff is all arcane knowledge and ancient Druid lore to me, so I'll have to wait.

[M249Joe]

Thanks for posting the thread.

[dumfounded]

This is an interesting read, although beyond my electronics experience. I recently had my fourth strip installed and the mechanic claims the new strip was a re-designed part bearing the same part number. Anyone else have confirmation of this?

[deilenberger]

This is an interesting read, although beyond my electronics experience. I recently had my fourth strip installed and the mechanic claims the new strip was a re-designed part bearing the same part number. Anyone else have confirmation of this?

Sounds like an optimistic mechanic. My latest one was installed by the head-tech at our friendly local dealership. I asked him if this was from a different vendor or better design.. his reply was "Nope - BMWs plan is replacing them regularly.."

You just have to make sure it fails at no more then 23 month intervals (since the 2 year parts warranty then covers it..)

[deilenberger]

Don, I read the page 6&7 of the linked thread. They talk about a heater strip. What are we heating? Is this the low fuel lamp? It would be nice if we could keep the low fuel lamp when bypassing the strip. I don't know what triggers the lamp though. Do you know?

I have a short piece of a failed strip on my desk..

The heater strip is one one side of the sensor, the level strip is on the other. Voltage is passed through the heater strip to warm the sensor up. The other side is a "varistor" type of strip - where resistance changes with temperature.. the fuel tends to cool the part of the strip that it is immersed in - so the resistance of the sensor side of the strip will change with fuel level.

So - we're not heating the low fuel lamp - and no - there is no way to keep the low fuel lamp when the strip is bypassed since the low fuel lamp is triggered (partly) by the fuel level measurement.

[hjsbmw]

The heater strip is one one side of the sensor, the level strip is on the other. Voltage is passed through the heater strip to warm the sensor up. The other side is a "varistor" type of strip - where resistance changes with temperature.. the fuel tends to cool the part of the strip that it is immersed in - so the resistance of the sensor side of the strip will change with fuel level.

How does this compensate for varying ambient temps? Is it self-calibrating? Otherwise, if the only reference is the resistance of the immersed strip it would seem that a bike should have a tendency to show gas lower than the real level after having been parked in the sun (higher temp = higher resistance, similar to an empty tank where a smaller portion of the strip is cooled by the gasolina).

[finsally]

I am taking my bike in to the dealers tomorrow to have the fuel strip replaced (£190 quoted by dealer) when i said this appered to be a rather common fault his reply was we have only had one or two!!! Independant mechanic I spoke to in the hope he could do it said he had spoken to some mates at the dealership and they said they change them on a regular basis and it would hsppen again.

Not sure if the warrenty is 2 years over here in the Uk does anybody know?..chances are it will only be 1 year.

Cheers Bob

[deilenberger]

The heater strip is one one side of the sensor, the level strip is on the other. Voltage is passed through the heater strip to warm the sensor up. The other side is a "varistor" type of strip - where resistance changes with temperature.. the fuel tends to cool the part of the strip that it is immersed in - so the resistance of the sensor side of the strip will change with fuel level.

How does this compensate for varying ambient temps? Is it self-calibrating? Otherwise, if the only reference is the resistance of the immersed strip it would seem that a bike should have a tendency to show gas lower than the real level after having been parked in the sun (higher temp = higher resistance, similar to an empty tank where a smaller portion of the strip is cooled by the gasolina).

Only the BMW engineers know that.. I do know that once I filled up with some exceptionally cold gas on a warm humid day (the tank actually started sweating from condensed moisture on it) - and the fuel gauge stopped responding until the tank warmed up. I imagine they might use the ambient temperature sensor to guess where fuel temperature might be (wonder if the "Booster Plug" which changes the readout from that sensor has any effect on level readings?..)

[hjsbmw]

Only the BMW engineers know that...

True, unfortunately.

What bugs me the most about the fix in the thread you posted is that they have to apply a voltage where there apparently is none in a working strip. Other than that I think it's an interesting find.

[roger l]

My fuel strip went out last summer. I put a piece of black tape over the fuel low light and rode that way all summer until I had the strip replaced in the fall. I am a mechanical guy, electronics scare me. I have let the "magic smoke" out of too many things. I will stick to the black tape.

Roger L

[Fjm]

(wonder if the "Booster Plug" which changes the readout from that sensor has any effect on level readings?..)

The Booster Plug doesnot appear to have had any effect on the fuel level readings on my bike.
I dont think I will ever trust the fuel strip and work on odometer reading to next fill. Having said that, the same applies to cars!

[dbrick]

My bike's fuel strip is still OK, but I was interested to see this ADVRider post:

http://advrider.com/forums/showthread.p ... st21268240

which describes how to make a tool to repair them. Posts #48 and #56 in that same thread provide more info.

[hjsbmw]

Very interesting.

[thepeacebullgrunt]

Oh lord! I am reading you guys... and I am lost.

Are we talking about a fix when the fuel sensor contribute to wrong estimate on the dashboard...

My R got that problem since almost now 2 yrs...
it estimate 140 miles maybe 120 until the bike stop dry dead on the freeway if I didn't preemptively refill before.

My mechanic is just all fuzzy about it...he don't look like he is excited at all to fix the mess.
He keep saying... "Sometimes it goes away by itself".... dude!

[Newportcycle]

Oh lord! I am reading you guys... and I am lost.

Are we talking about a fix when the fuel sensor contribute to wrong estimate on the dashboard...

He keep saying... "Sometimes it goes away by itself".... dude!

I believe they are talking about when the fuel strip goes dead, not just inaccurate reading. The fuel strip in my new bike was dead 30 miles from the dealership, at the 600 mile services it was documented, we will replace at the 6000 mile service later this summer. I like the lighter idea, if I was off warranty I would try that, well by the sounds of it I will have ample opportunity in the future.

[Bob Ain't Stoppin']

My bike's fuel strip is still OK, but I was interested to see this ADVRider post:

http://advrider.com/forums/showthread.p ... st21268240

which describes how to make a tool to repair them. Posts #48 and #56 in that same thread provide more info.

Oh Boy! Don is going to have a great time with this one

[dbrick]

My bike's fuel strip is still OK, but I was interested to see this ADVRider post:

http://advrider.com/forums/showthread.p ... st21268240

which describes how to make a tool to repair them. Posts #48 and #56 in that same thread provide more info.

Oh Boy! Don is going to have a great time with this one

A little experimentation might be more attractive if the fuel strip fails after the warranty expires.

[deilenberger]

My bike's fuel strip is still OK, but I was interested to see this ADVRider post:

http://advrider.com/forums/showthread.p ... st21268240

which describes how to make a tool to repair them. Posts #48 and #56 in that same thread provide more info.

Oh Boy! Don is going to have a great time with this one

It's ummmm.... interesting. I've always thought the problem is in the junction between the strip and the wiring - which is encased in a block of plastic epoxy (and non-operable.. at least I couldn't get one apart without destroying it.)

Right now mine is working - but when it goes (just a matter of time IMHO) - be sort of fun to try this.. probably won't blow the bike up, especially if done on a full tank where the junction is under fuel.

Thanks for the link, I'd heard about it but never seen it.