Dave and I are in the midst of troubleshooting why our newly bought bike won’t start.   The fuel pump initially would not run so that was a mission Dave was on for the first half of the day.   He now has the fuel pump running but during the process of me cleaning out the fuel tank, I bumped some wires on the fuel level sensor disconnecting them.   I believe one was for the fuel pump connector that connects under the seat.   Against my better judgement Dave decided he could try the newly fixed fuel pump without the pump connector . Below is the picture of his set up.     When the starter was pushed, it would try to start but wouldn’t. 
Question.   By not having that connector hooked up, is that making an open circuit not allowing the bike to start? I hope that made sense.   The pump ran, gas ran up and through the rail, but no start.  Spark plug was wet. 

From what I can see that should work as you don't need the connector except to power the pump and the fuel level sensor.
That sure is a nice clean K was it like that when you got it or is it all your own work.

Check that the big connector on the ECU (under the seat) is seated correctly. Then check that the connector for the ICU (under the main tube behind the headstock) is also secure.

What do you mean by 'try to start but it wouldn't'? I'm with Rick - that setup looks like it should work.

Thanks! Dave was able to start it, had it running for a min. Or so, then died.  Had it running again long enough to record an audio file to share with me as I was in the house.  Now it hasn’t started again.  Dave thinks the injectors might be dirty. But , we had it going which is exciting!  Now to figure out the next step.   

When I said it wanted to start I meant it would turn over but not start. Dave said I said that wrong. 
Dave said i need to say he is the man, and I have restored faith in him .

RicK G wrote:From what I can see that should work as you don't need the connector except to power the pump and the fuel level sensor.
That sure is a nice clean K was it like that when you got it or is it all your own work.

The bike was surprisingly clean when we got it.   The only thing that has been really bad so far is the rusted fuel level sensor which I think was from the last guy trying to get it to start left the gas tank opeN for a long time.    I did wipe up some of the dust under the gas tank when I removed it but I expected it to be filthy. 
I’m not sure where I’m gonna find a replacement part.  I read they are hard to find

Injectors can be cleaned at home there are Youtube sites explaining the process. You can also test the pattern by removing the injector rail with the injectors still attached. Insert the injectors into four clear bottles crank over and observe the pattern. Care needs to be taken while doing this refrain from smoking or causing sparks. Flow testing can be done by measuring the amount in the bottles over a given time. To be dead accurate you can buy a graduated vessel. I bought one from a home brew supply shop for $10.00Au.
Regards Martin.

To get rid of the rust remove the sender from the tank (4 Phillips screws underneath) then soak it in some 10 - 1 water molasses mix for a day then clean it off and all the rust will be gone. They are fairly reliable and it should be OK. You may need a new O-ring I cant remember the size but someone here will chime in. Get a Viton type it will last much better.

Kath if you do test the injectors on the bike you best have a fire extinguisher on hand. On one of the other Brick sites one member while testing his injectors set his Brick on fire. He wasn't hurt but his Brick sustained a fair bit of damage. So you need to thoroughly make sure you have no sources of ignition and have someone with an extinguisher on standby. might also be better to do this outside in a well ventilated area. I have asked for the source of ignition and I will post the answer.
Regards Martin.

hi kath
most fuel level sensors I have seen are rusted on the framing , to some degree

I don't think that is an issue at all , but the electrical connections do need to be solid and uncorroded , by that I mean if there, is a soldered joint to part of the sender make sure it looks clean or without dimples in the soldered joint
the corrosion can be cleaned off with a tooth brush type brass brush and solvent

what is important is that the wiper contact  that moves across the windings of the sender unit is clean , almost all could do with a clean up , and if the sender has intermittent operation , the windings can also be carefully cleaned up with a very fine grade of wet and dry to expose the copper wire so that the contact between sender and wiper is consistent , likewise the small disk of conductive metal in the plastic retainer (indicates when tank is at low level ) and its wiper .

practical mechanics will guide you to make the sender float move freely and that the action is smooth
I recently got a faulty sensor from motor works in England for not much money at all . as it arrived ...hmm was dubious but with the work I just described had it working correctly  in under 20 minutes , just takes patience and attention to detail

cheers

charlie99 wrote:hi kath
most fuel level sensors I have seen are rusted on the framing , to some degree

I don't think that is an issue at all , but the electrical connections do need to be solid and uncorroded , by that I mean if there, is a soldered joint to part of the sender make sure it looks clean or without dimples in the soldered joint
the corrosion can be cleaned off with a tooth brush type brass brush and solvent

what is important is that the wiper contact  that moves across the windings of the sender unit is clean , almost all could do with a clean up , and if the sender has intermittent operation , the windings can also be carefully cleaned up with a very fine grade of wet and dry to expose the copper wire so that the contact between sender and wiper is consistent , likewise the small disk of conductive metal in the plastic retainer (indicates when tank is at low level ) and its wiper .

practical mechanics will guide you to make the sender float move freely and that the action is smooth
I recently got a faulty sensor from motor works in England for not much money at all . as it arrived ...hmm was dubious but with the work I just described had it working correctly  in under 20 minutes , just takes patience and attention to detail

cheers

Thank you Charlie.   My bull in a china shop approach caused two electrical connections to be disconnected.   Can it be re soldered?  Secondly, the windings have been cleaned to harshly also and some are not connected any longer.  The wiper now moves freely, but with the other two damages I’m wondering if I need to find a replacement? Which so far is pricey and hard to find.

Hi,

This post describes the O-ring size. Tisk, tisk Rick, it was the answer to your question back in 2011.

Rust on the sender is pretty normal and doesn't disturb the operation of the unit so long as the rust doesn't get into the float arm pivots. If you haven't seen it, check out the page I wrote on the fuel sender.  https://www.k100-forum.com/t9265-messing-with-the-in-tank-fuel-sender

Where were the connections you disturbed?  On the fuel sender itself, or on the wire outside the tank?

If inside on the fuel sender itself, that could be tricky.  The wires are probably old, the insulation on them very brittle and easily broken.  Getting at the soldering lugs on the gas tight connector for rework is challenging but not impossible using the right tools (temp controlled soldering station, solder wick, & silver solder) and techniques.  The wires are immersed in fuel their entire life and so if you need to replace the fuel pump wires, they need to be PTFE insulated and not normal PVC.

If outside on the connector that connects to the harness, then repair / replacement is easier.  If the wire broke from a pin inside the cylindrical connector, then it is best to replace the entire connector pair on the tank and at the harness.

robmack wrote:Hi,

This post describes the O-ring size.  Tisk, tisk Rick, it was the answer to your question back in 2011.

Rust on the sender is pretty normal and doesn't disturb the operation of the unit so long as the rust doesn't get into the float arm pivots. If you haven't seen it, check out the page I wrote on the fuel sender.  https://www.k100-forum.com/t9265-messing-with-the-in-tank-fuel-sender

Where were the connections you disturbed?  On the fuel sender itself, or on the wire outside the tank?

If inside on the fuel sender itself, that could be tricky.  The wires are probably old, the insulation on them very brittle and easily broken.  Getting at the soldering lugs on the gas tight connector for rework is challenging but not impossible using the right tools (temp controlled soldering station, solder wick, & silver solder) and techniques.  The wires are immersed in fuel their entire life and so if you need to replace the fuel pump wires, they need to be PTFE insulated and not normal PVC.

If outside on the connector that connects to the harness, then repair / replacement is easier.  If the wire broke from a pin inside the cylindrical connector, then it is best to replace the entire connector pair on the tank and at the harness.

Two wires broke off on the fuel sender. I’ll attach a picture of how it started and where we are at now.  We are thinking not fixable.  There is other damage to the board also. Dave is trying to figure out a way to wire the pump wires another way without using that sender for just now to get it running.  Then we will order a new one when we know the bike is going to able to run .   Any suggestions are appreciated . 

Just an FYI but if you need to order any new parts from BMW and are in the US, A&S Cycles sells parts with no tax and free shipping regardless of the order amount. That's where I get parts.

https://www.ascycles.com/

Kathysresto wrote:

Well that ain't pretty! A few of words spring to mind...toast, cactus, kaput. Good news is they do seem to be available - second hand from a reputable dealer and not too pricey considering.
https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=4&NU=10&M=40&Ct=IA

Motorworks also does the O seal (referenced in the attached link). I know they ship to Oz...presume they ship to the US too.

There is a new thread at Motobrick.com about a 1993 K75 that caught fire and will probably be parted out.  Many parts are interchangeable between your bike and the toasted one, particularly the stuff in the fuel tank.  I don't know if the fire got to the wiring under the tank, but you might want to check it out. 

http://www.motobrick.com/index.php/topic,11273.msg98312/topicseen.html#new

If nothing else, it is a good warning about playing with fuel injectors.

Well, Born Again Eccentric is absolutely correct; I agree.  That sender is toasted.  It's not so bad that the variable resistor plate is torn up.  That would mean you couldn't use the fuel level indication.  But the gas tight passthrough connector is beyond repair.

You are going to have to search online for a replacement sender.  Search far and wide.  I found my replacement fuel sender by going to ebay.de.  Also try ebay.nl and a neat little Dutch breaker's yard I found by chance once.

Point-Seven-five wrote:it is a good warning about playing with fuel injectors.

Which is why I don't bother playing with fuel injectors and just send them off to http://www.mrinjector.us/

Very scary stuff seeing that bike knowing what Dave was doing yesterday could have resulted the same way.  I’m glad we did t need to mess with the injectors. 

Thank you all for the leads on a new gauge.   We found one for 200, but hoping to keep our eyes open for a little cheaper/ used one.   I’m not feeling good about asking that man who’s bike was just burnt quite yet.  
In the meantime Dave took the soldering as a challenge and low and behold, he did it again!    He was able to get the connections , and just removed the fuel gauge components for now.  We are running to the store to get two new fuel filters and gas it up.

He was able to get it running well this morning with his gas in the bucket contraption.  We will see now that the entire thing is cleaned up and put back together.  
Wish us luck!

robmack wrote:Hi,

This post describes the O-ring size.  Tisk, tisk Rick, it was the answer to your question back in 2011.

Thanks Rob I cant claim a failing with age brain because I have never been able to find old posts. I shall now put that size into my notes.
Oh and BTW whats your excuse it was 2016

I found a good used one that was like new on Ebay for mt 88 K100 last spring for 30 dollars US The O ring cost 8 bucks at the local BMW dealer.My bike sat for 13 years with old gas in the tank and everything in the tank looked like your photo . Good luck with it.

[quote="RicK G"]

robmack wrote:
Oh and BTW whats your excuse it was 2016

I am defenceless. Failing brain cells here too apparently.