Camhead fuel level sensor retrofit?

[blalor]

I'm sure this has been discussed but searching didn't turn anything up. The fuel strip on my '07 RT has just failed. I thought I'd gotten a "good" one, but apparently that's relative…

 

I found a forum post on ukgser that discusses using a float sensor instead of the fuel strip. I haven't found a similar conversion for the RT, but the Camhead (K26 R 1200 RT 10 0430,0440) uses the same fuel tank as my '07 but has a float sensor: https://www.realoem.com/bmw/enUS/showparts?id=0440-USA---K26-BMW-R 1200 RT 10 (0430,0440)&diagId=16_0823 

 

Has anyone retrofitted this sensor to the older bike?  @dirtrider I know you always pop up first on these kinds of threads, but I suspect this is an area you'd have some familiarity with. I haven't looked at other parts to see if the pump or other parts in the area have changed.

 

Thanks!

Brian

[dirtrider]

10 minutes ago, blalor said:

I'm sure this has been discussed but searching didn't turn anything up. The fuel strip on my '07 RT has just failed. I thought I'd gotten a "good" one, but apparently that's relative…

 

I found a forum post on ukgser that discusses using a float sensor instead of the fuel strip. I haven't found a similar conversion for the RT, but the Camhead (K26 R 1200 RT 10 0430,0440) uses the same fuel tank as my '07 but has a float sensor: https://www.realoem.com/bmw/enUS/showparts?id=0440-USA---K26-BMW-R 1200 RT 10 (0430,0440)&diagId=16_0823 

 

Has anyone retrofitted this sensor to the older bike?  @dirtrider I know you always pop up first on these kinds of threads, but I suspect this is an area you'd have some familiarity with. I haven't looked at other parts to see if the pump or other parts in the area have changed.

 

Thanks!

Brian

Afternoon Brian

 

I don't personally know of anyone that has done a full float conversion on the 1200RT (hexhead).

 

My one BIG concern would be IF the electronics on your 1200 hexhead could read & process the float sensor output even if you could get it to fit in the tank. 

 

Th original fuel strip uses a different type function to tell fuel level so my guess is that you would have to figure out how to get a float sensor to interface with your present motorcycle's electronics.  

 

 

 

 

[blalor]

I think the GS-specific post I linked shows some wiring and coding/configuration modifications, so I’ll try to chase those down for this bike. I know enough electronics to be dangerous so it’s possible I could hack something together if necessary, but it would be nice to find a manufacturer-adjacent solution to this crappy design!

[Ron-M]

I have had my fuel strip replaced in my 07 RT 11 times.  I have asked about converting to the float system and was told that it could not be accomplished due to Dirtrider's response to your inquiry.  

[blalor]

I have a wiring diagram from a Haynes manual for my bike, but it doesn’t cover the camhead. It appears the central chassis computer (which I *think* is what the fuel level sensor connects to) is shared with all RTs 2003-2014. Does anyone have a wiring diagram for the later models? Are those in the reprom? That other thread discusses coding to change the sensor type. 

[blalor]

Ah, same book, but for the GS:

 

And the GS and RT share the same central chassis computer. I’d love a diagram of the computer… Anyway, I’ve ordered a float sensor from eBay, $60 shipped. We’ll see if I can make this work. 

[Ponch]

There's a thread on the MOA forum where someone did a float conversion, but it wasn't a cam head one, I think. I have it saved as a PDF if someone wants it. https://www.dropbox.com/s/5lg7yxb43blzhln/float conversion.pdf?dl=0

 

[blalor]

Thank you, @Ponch!

[blalor]

It works! It *may* be reading backwards (empty is full) but I’m not positive, yet. 
 

These two photos show the float connected to the bike and the display reflecting a working fuel gauge. I had to swap the positions of two wires at the ECU and make a change via the GS911. Now to swap the pump housing and finish my write up. I’ve got about $200 into this project, including the extra float I bought and didn’t need. OEM parts would run about $600 for the new fuel pump assembly. I got mine used from the lovely folks at https://www.motorworks.co.uk/

[Kmclain]

Did you figure out how to get this to work?  I am in the same position on my 08 R1200RT.  After swapping the wiring and doing the coding, it is registering on the gauge backwards.

[blalor]

Oh thank god it's not just me!  No, I haven't solved it. I guess it's worth re-verifying the wiring to make sure I got it right, but I've only got the one wiring diagram, so if that's wrong there's not much I can do. The solution I've basically settled on is making a circuit that uses a digital potentiometer to effectively invert the signal, ie having it read proportionally but from the other end of the scale. A small microcontroller would be needed, but I think it can be done small enough that it'd plug right inline with the sending unit.  

[blalor]

In retrospect, this is probably exactly what the proebeemer.nl FC2 thing does… https://www.proebeemer.nl/producten/float-control-2-voor-r1200rt/

[Kmclain]

The proebeemer one converts the resistance into the Kohms range needed to use the circuitry of the foil sensor.  It doesn't seem like that would be very accurate.  That is why I was hoping this way would work.  It is strange that it does work on the GS but not on the RT.  It just must have something to do with the instrument cluster in the RT.

[blalor]

Ah. Yeah, I agree it is weird. I have a lot of balls in the air right now but I’ll try to make that circuit soonish. I’d love to have a working gauge that doesn’t require me to get gas when the tank reads full…

[Capt B]

Hi! 2008 R1200RT  ---float conversion reads backwards-
Did either one of you guys ever get your indication to read correctly? I just put in a 2012 OEM pump/float and repinned ZFE and used GS 911 to re-code. All went well. My indication also appears to be bass ackwards. Any help would certainly be appreciated! All of the parts fiche show this fits the bike – do we need a re-flash? Or is there a simple work around? The easiest thing is the flip the float potentiometer 180° but then you would have to re-engineer the entire float arm etc. because of the curves in the tank. It's strange that these drop right in the mid 2010 on up no problem.

Thanks, 
Capt. B 

[blalor]

I still have the parts! And I still haven’t built the adapter… 🤦‍♂️

[Capt B]

Thanks for the reply, Blalor!    I'm new to the board- although I've attended a few events – three times at Weaverville, once at Red Lodge and one N./South. 


UPDATE:  So....with some McGyvering,  I was able to invert the  potentiometer/reverse the operation of the float... and so far my (test) indications are indeed correct... and the indications appear to be quite accurate.

(Again- this is with the a post 8/2010 OEM pump/float out of 2012 RT. It dropped in to my 08 RT ESA with a minor modification of the retaining ring, because the orientation is about 80 ish deg off from my 2008 RT. (I think if I had to do it again I would just grind the tab off the fuel pump mounting flange, so I could rotate it freely – (use index marks  to make sure the pump doesn't rotate when you're tightening the cap) because the retaining ring is brittle. (I did order a 2012 retaining ring and we'll see if it fits my 08/01 tank. Dealer says it may… Or it may not.

COMMENTARY/WHINING:  As with a lot of BMW Motorrad, parts, part numbers are/ can be exactly the same...but the actual part (for your application) may be different! --based on manufacture date of your bike. Frustrating. And my local dealer parts counter staff periodically expresses the same frustration.  For example the 2012 retaining ring is the exact same part number as my 08,  but when I look at photos it has the diff 70-80deg orientation – Real OEM and other dealer sites say the ring "fits a 2008 Rt... " even when I enter my Vin number... but it WON'T fit ....with the 2008 pump! I had the same experience just buying the float separately – there's no place to mount it on the 08 pump. in other words it didn't fit.   Why don't they just change the (new part) part number? I ran into the same issue replacing an entire gearbox once. Put a 2010 GSA Enduro gearbox in a 2009 GS. SAME part number. Fit by vin number. Verified prior to purchase with dealer. Different transmission and gear ratio --hooked it all up. Bike won't start. Computer can't tell if it's in neutral! Why? Well the gear indication potentiometer had been totally redesigned in 2010.Bike  DOA  as far as gearbox electronics went. (Surprisingly -or not-huge local dealer svc said they didn't know what to do about it.)  Thank God for GS 911 learn function! It worked out fine)  Whatever -maybe  I'm missing something w Motorrad p/n logic?

 

K-back to the project: inverting  the potentiometer/swapping float arm, by default, now put the float on the forward side of the tank (vs 2010-on rearward) which is much narrower.  This necessitated some very creative bending and trial and error to keep from float hangups. Really critical. Took a couple hours of trial and error and I was always afraid of breaking the potentiometer or float) Plus, I got tired of transferring fuel in and out, so for ease and safety sake, I tested the set up/ float arm bends- easily, safely and repeatedly- by filling the tank (off bike) with a garden hose (I know I know- I thoroughly dried and blew everything out with compressed air and of course I didn't connect fuel lines/operate the pump – and blew/dried that out also before I refilled with fuel) while monitoring movement/adjusting arm/position of pump with a meter.. So far it reads 89 Ohms when empty/ 6 Ohms full. New 93.7/ 3.2 so it's nearly perfect full travel.  (I did test once w/full  water connected to the bike – see pic below – no more triangle!)
Tested w/ fuel today on the bike –dumped in a gallon and it registered about an 1/8th -the absolute bottom- which is perfect for 1.1 gal reserve....and w/ about 3 1/2 gallons (all I have on hand) total, it reads just below half.. Bike on center stand- side stand up. So far so good. 

Unfortunately,  I haven't done a test flight to check for on the road potential  binding/ proper indications yet . Ugh.the.absolute very last thing I did before test ride today was connect the return fuel line. Well, because of the 70/80 deg orientation difference of the 2012 pump, the return line hose interferes with the pressure line connector -and I foolishly cracked the plastic connector elbow – because I was a little impatient. (I had connected them numerous times and while there is interference, it wasn't a big problem – the problem was me!)  I'm going to put a slightly longer fuel hose on the new connector elbow though- ($34 part is enroute)

So.....I'm 95% there – I'm hoping it'll be a total success. . Once  I get the connector part and do thorough road testing I will update. If it's not successful i.e. if the float hangs up --enough to be an annoyance (I believe our machines should operate as designed ) when bouncing around on the road…..then this work is prob not worth it.. And I wouldn't wanna lead someone down the garden path. You could of course experiment with filler neck mounting (K-Bike) but the RT tank is just so funky, I don't necessarily think it would be that accurate. But that's just a guess -I haven't attempted. (Note-of course I've always used odometer as primary-but it's nice to have secondary Flight Display confirmation for the once in a while when you forget to clear the odometer) 

MORE COMMENTARY/WHINIONG: I can only surmise, (WAG?) without doing research, that there must be some firmware difference in the mid 2010- on -float equipped bikes -because on those bikes, the indication is -of course not reversed. Drop in plug-in play. A little frustrating that the GSA and K bikes can  just drop a float in...re-pin it re-code and all is good, (while 05 RT /388 indication is reversed) I looked at both of those other applications extensively.... and their potentiometer orientation is comp[letely different. (BTW I bought a new 2010 on float.... first...and extensively tried to mount it to my stock 08 pump --but I finally gave up and bought the eBay 2012 pump. I had the same potentiometer orientation problem, and that-- coupled with the orientation of the 08 pump base/body--completely different pre-August 2010-- just made it near impossible to do without the float hanging up. In theory it's possible if you get it just right and spend some more time but I spent quite a bit of time.  So anyone out there:use caution if you buy the 10-13 RT BMW float --parts fiche says it fits... but reminder- that's based on you having a post 2010 pump also! 

So far I have $251 in for the eBay '12 pump. Currently a new strip membrane is $243+ tax.  
Having had to reverse the float and the orientation.... I think if I were to do it again.....right now I'm 51/49 - but would prob might just buy an "improved" strip (particularly the $135 Argentinian version)  and hope for the best. (Having said that I had 10 years out of my third replacement strip on this bike and right now I have nine years on the second replacement strip on my GS so I've been really lucky compared to the horror stories of others.) Lot of trial and error involved here. And... I thought I could just drop a 2012 pump in and be done. NADA.  

I'll report back after I run a few tanks through it. And if I have to pull the pump again – I'll certainly take pics of the float orientation. I thought I had done that. My bad!  Apologies. I wasn't thinking about posting anything. So anyway-the pics below show  (look closely-mod  is on the left)- I popped the float out of the support arm and reversed it 180° and supported it w/ stainless steel AN safety wire. Not ideal... but it doesn't move a bit and is really sturdy ..and it's the only way I could invert the potentiometer without really getting creative electronically.... and I just didn't want to bother. I just want to ride with accurate information and no flashing triangle!  (The float on the right is the stock mid 2010-13 float/orientation) 

Finally-after having done all this – I had to do so much bending on the float arm etc. you could/would be much better off- financially-and possibly much less bending and trial and error Dash by just getting a cheap automotive (6ish ohm Full/-93 Ohm empty) float and bend that..... and then  figure out someway to zip tie it, safety wire/screw it to the pump base (and possibly grinding the base facilitate a mounting point) Float pointing  with the float pointing towards the filler neck– but it's got to be really precise ....so I would model it after the 10-13 stock float set up –if possible-it's just incredibly tight in the tank with the odd shapes-anyway  you could try it for $20 instead of 200+. OEM .  Used oem floats been hard to come by on eBay... admittedly I've only looked for a few weeks though.
.
I hope this is helpful…

Capt. B