General Category > General Discussion
Fuel Strips (Film type fuel sensor)
Inspector Gadget:
PS: I just ordered the floater-type fuel-pump.
I can chew on it for ever, but having it in front of me will help my creative juices going. ;D
Haakon:
Very good explanation "DutchMidiMan"- thanks.
Both the the probable causes, repairs and modifications.
I was afraid I had stirred up a "hornets nest" by my unqualified post re this. :)
I have no idea at all to what sort of signals are used. The industrial standard are 4 to 20 mA (0 to 20mA is used but not often)
IF BMW use a 4 to 20 mA signal range there are lots of SIGNAL CONVERTER`s that can be used.
That is the reason I wrote what I did. The strip is more linear than most common floats but the difference is academic.
Here you have a link to the first link to direct converter I found- from sliding resistor to mA output.
http://www.acromag.com/catalog/119/Signal_Conditioners__amp;_nbsp;Converters/Signal_Converters,_Transmitters/Slidewire___Potentiometer_Input
This type of converters are used all over in industries- so the price may be way too high.
I am sure cheap editions can be found! I guess a 5 to 10 % in the full tank readings are not important?
Its more important to have exact readings when the fuel level is low?
Some such converters can be programmed all over the range but they cost more.
If BMW use a value range outside of 4 to 20 mA that too can be "faked". (compensated for)
Could you or some other hook up a mA instrument so we know the range?
(We need to know the mA at full and empty fuel level- with a working strip :-)
------------------
I must re- read you post- I am too tired and have had a glass of w...ne.
Haakon
PS- I am NOT a "electronics" or automation and measurements engineer. That said, even I manage to set up that sort of converters :-[
Inspector Gadget:
You're welcome, of course!
Recognized the signal converters!
Having family working in the process automation and having attended a few classes myself in university. However, chemistry definitely not being my thing (or mathematics to a certain extend) I figured it would not be my parse. :-[
(although I do remember indeed 4 mA minimum, so that 0 mA would indicate a broken connection/loop, or something along those lines)
Don't worry about the hornets, all creatures are equally important on this earth. ;)
I agree that the resistive measuring part of the fuel-strip will be likely indeed linear.
Logarithmic is usually only on the volume-knob of the radio as our hearing also logarithmic.
(and the tone-knob usually being of the linear type pot-meter)
But, the good news is that I believe the clue is being already been found with the "FuelStripSpoof_v2.jpg";
http://bmwsporttouring.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=770085&page=6
The 2K resistor being enough to fool the ZFE that the tank is full.
And the current being limited via the 1M ohm resistor.
(mind you: the measuring-part of the fuel-strip then needs to be disconnected as stated by the author).
But lets wait and see what the floater-type resistance-values are, it is currently underway to me. 8)
I can't take measurements on my 1200RT as the fuel-strip already failed, it shows permanent tank-full. Because most of the fuel evaporated because I wasn't able to ride a bike for a long time because of chemo-treatment and acute type-2 diabetic. :(
Inspector Gadget:
And received the floater-type complete (!) unit this morning, including fuel-pump, electronics, the works.
And that only for 110 euros/152 US$/1567 ZAR. Including shipping. :D
First, some good news;
- The floater is mounted onto the fuel-pump assembly, so it is all "one part", the floater is *not* hooked into a holder inside the fuel-tank for that matter. Unlike the fuel-strip version, that needs to be hooked into the bottom of the fuel-tank and on the top of the filler-cap.
- The connector to the floater-output (variable resistance) is the same, 4-pin connector as with the fuel-strip version, with the same pin-layout. (the middle connections are used for the sensor, and with the floater-type the two outside, remaining pins are not connected)
So, in that respect, "plug-and-pray".
- The measuring part appears to be a ceramic printed circuit boar (pcb) with deposited substrate resistors and sliding contacts that will, so it appears, add more resistors (in serial) as the floater moves.
I just took a "quick-and-dirty" measurement with my (digital) ohm-meter directly on the solder-contacts of the ceramic pcb:
Tank Full: 86.6 Ohms
Tank Empty: 3.4 Ohms
Remarkable detail:
Some of you may know about the current BMW Recall action regarding leaking fuel-pumps because of the cracked seating of the (plastic!) quick disconnect?
According to the records I have this good-as-new fuel-pump is of February 2012, and already (!) does contain the formal fix that BMW has released, being a metal ring around that seating.
Meaning, at least in my book, that BMW already knew about this problem! :o
-
kobus:
I spoke to a few guys regarding fuel strips at the BMW MOA Rally, and most of them told me that BMW in the US has extended the warranty on the fuel strips in the US until something like 2018, so they just go to the dealer and have it replaced for free.
Does anyone know if this is the case in Europe/elsewhere as well?
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