K11 Owners Group

bikerdavy · Last edited by bikerdavy on Sun Jun 21, 2020 10:29 am; edited 3 times in total

My Dad and I have been wrestling with the K1100RS not starting. We think it's the motronic unit and have had a couple exchanged with little success (although once it worked, briefly). To be honest, we're kinda getting to the end of our tether with it and are thinking on giving it up, as we've been trying to get to the bottom of this for about a year now. It all started a year ago when I tried putting in a new battery - the electrode posts were a different configuration so I had to move and pull the cables a bit, then the next day the bike stopped of it's own accord on the motorway/freeway. I managed to nurse it to work, and thereafter it started and stopped occasionally for a brief spell then just refused completely. Confused

The basic issue is- battery in, motronic in, key turned in ignition, kill switch vertical, but no swoosh from the petrol/gas pump in the tank and no life in fuel gauge and brake lights don't work. (probably more too, if previous troubles with previous motronics are anything to go by.) Press start button and starter turns engine, but no life other than that - bike doesn't start. In fact, the position of the engine kill switch does not seem to affect bike's behaviour at all. Side stand is up. Clutch in. (ps, starter works with kill switch turned)

My dad has a big list of checks he's done which I might go into later.

One time when we put in a replacement (second hand) motronic unit, it worked fine with no issues, but that was last November, then come this spring when we started getting it ready for use again, it was dead, and has remained so these past months despite my dad's (and my) best efforts at trying to get to the bottom of it. One possibility is my charger might have fried something?

Some more info re problem is:
Kill switch area has been cleaned and looks fine; No power at all to (What I'm 99% sure is) Rear brake connector when powered up; Side stand switch jumped does not help;

(The following relay checks done on a previous motronic unit but everything still seems the same now) My Dad devoted a lot of time to studying the relays. To discuss the 4 pin relay that works the fuel pump and injectors- 12V is getting to (low power side) relay pin 86 from the side stand, but the motronic unit MCU is not supplying a ground to (low power side) pin 85. If motronic MCU did supply this ground, it would activate the relay and allow the 12V that is at (high power side) pin 30 to connect with (high power side) pin 87 that powers the fuel pump and injectors. This would allow at least the fuel pump and injectors to work. So what we need is the motronic unit MCU to supply this ground, or find out why it isn't supplying it.
But when my Dad induces a false earth to terminal 85 on each relay the relays work, so the fuel pump works and injectors get power, but more is needed because motronic unit needs more than false earth to allow the bike to run. Well, that's how we understand it anyway. It's getting into more complicated stuff, hope folks can still help. (Updated above paragraph 21/6/20 1530)

Thanks for any help you might give! I hope I've been clear enough and not given info overload, but I'm hoping this might be of help to getting to the bottom of this.

I started to discuss this in the Campfire where I said hello, but thought it might be better to bring it to the tech part where more folks might see it. Duck was a lot of help, thankyou! but we never quite got to the bottom of it and I wanted to make use of the Saturday if folks might be around and willing to help after Duck has gone to bed (who lives in Australia, as i gather).

Flying Duck · Posted: Sat Jun 20, 2020 2:28 pm Post subject:

WA is Washington State in the US and is not part of a former penal colony. Laughing

_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

bikerdavy · Posted: Sat Jun 20, 2020 2:36 pm Post subject:

Sorry Duck!
I had no idea WA stood for that, but I googled it and "West Australia" came up on my phone! Bumf*** wasn't too much help, you understand! Laughing

Thanks again, though I really appreciate it. Very Happy

I added in some stuff from our conversation which hopefully should help things along. Please feel free to continue with anything that comes to mind for us to move forward.

flybd5 · Posted: Sat Jun 20, 2020 4:01 pm Post subject:

That thing about WA not being a penal colony is subject to debate! Smile

_________________
To err once is human. To do so repeatedly is incompetence.
1995 K1100LT SE

Grunter · Posted: Sun Jun 21, 2020 8:47 am Post subject: Non Starting

If there is no sound of the fuel pump operating, it may be worth while checking the power to the pump itself. The sudden break down after the battery change may be a clue.

Underneath the tank is the lead from the cover plate where the wires go though to power up things like the pump, level gauge etc.. I had similar problems to yourself but mine were intermittent - the most difficult to cure.

By pure chance I found the lead from the main harness which supplies the power was faulty and not making a good circuit. One of the pins was loose and the contact inside the moulded plastic plug has broken. As you cannot easily replace the section of the harness, it has to be replaced as a whole, what I did was cut both ends of the connector off and replace it with a 4 pin plug obtained from an accessory shop.
They are not as neat as the original BMW plug but they do the job. As it is hidden out of sight nothing is lost.

If you use a multimeter and connect one clip to the frame and then switch on the power and test each of the +pins and see if there is a problem. You
can check the earth but if the fuel gauge is working there is no point.
The replacement connector cost me about Â£4.
_________________
1997 K1100LT
1994 R1100RS

bikerdavy · Posted: Sun Jun 21, 2020 10:46 am Post subject:

Hi Grunter, - (Edited 22/6/20 1415 gmt plus 1)

All help much appreciated, thankyou! After rereading my explanatory section at the top about the relays, i realised it was as clear as mud, and i clarified it a bit more, at least i trust i have!

The fuel pump works fine when a false ground/earth is supplied to pin 85 of the fuel pump relay (just a jump wire to earth). That was what i was meaning when i was talking about the relay. When you supply your own earth to the low power pin 85 on the relay, (high power side of relay activates and) the pump fires up nice and strong. So any checks in the wiring between relay and pump will then be unnecessary. It's never been intermittent as long as this "false" earth is supplied to pin 85.

The question now is, why is pin 85 not getting the earth from the motronic MCU that it should be getting? The MCU will also be stopping other things from working, cos *when we get the pump running by supplying this "false" earth, the bike still doesn't fire up.

flybd5 · Posted: Sun Jun 21, 2020 10:47 am Post subject:

Did you check the main grounding lug below the fuel tank? Sounds like something came lose there.
_________________
To err once is human. To do so repeatedly is incompetence.
1995 K1100LT SE

bikerdavy · Posted: Sun Jun 21, 2020 3:14 pm Post subject:

Hi Flybd,
I'm pretty sure I've checked that one, but i can maybe check again. I have been through all the connectors under the tank cleaning them. Thanks.

Flying Duck · Posted: Sun Jun 21, 2020 3:58 pm Post subject:

Is the Motronic relay getting power and ground to 86 and 85?

All of the little black relays are the same so you can swap them around for troubleshooting. You can swap them into the horn relay holder to easily test them with the horn.

_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

flybd5 · Posted: Sun Jun 21, 2020 4:15 pm Post subject:

Scott_Anderson · Posted: Mon Jun 22, 2020 6:13 am Post subject:

It's not unheard of when the motronic fails to activate the fuel pump relay when trying to start the bike, the culprit could be the hall sensors either being bad, or bad connection.
HOWEVER, a hall sensor failure would not prevent the 'pump 3 second prime' when the key is turned on.

Have you checked for spark at the spark plugs when trying to start the bike. This can also give an indication of bad hall sensors if there is no spark.

Like flybd5 is thinking, if you have a bad ground to the motronic, it's not going to work correctly.

Have you checked for any motronic fault codes.

Don't want to assume the obvious, but just to confirm you are doing all this testing with the bike on the center stand and the side stand in the up position.
_________________
Ride safe.

1995 K1100LT 0302044
1997 R1100RT ZC62149
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)

flybd5 · Posted: Mon Jun 22, 2020 9:43 am Post subject:

Also, did you check that you properly installed the ground strap to the Motronic grounding tab on the side of the unit? If I remember correctly, forgetting that, or not putting it correctly, also causes most of the symptoms that you are seeing. Make sure that the ground strap hasn't been damaged either.
_________________
To err once is human. To do so repeatedly is incompetence.
1995 K1100LT SE

bikerdavy · Posted: Mon Jun 22, 2020 10:12 am Post subject:

Duck asked "Is the Motronic relay getting power and ground to 86 and 85?" -
- pin 85 on motronic relay takes earth from frame, same earth as starter relay. Starter relay works, so motronic relay *should* also work under assumption that wiring is good to motronic relay. *however* we will check this. Thanks Duck.

By the way, due to illness, i can't get to the bike to do checks today but hope to check stuff out soon.

Duck also said - "You can swap them into the horn relay holder to easily test them with the horn."
- Yes, we've done that, they are all ok. Thanks.

Flybd5 said- "That ground is not a connector, it's a central grounding bolt."
- Thanks Flybd, yes the certain grounding bolt had been checked and is solid.

Scott_ Anderson said "hall sensor failure would not prevent the 'pump 3 second prime' when the key is turned on."
Thanks Scott. We have replaced hall sensor, but still do not get the 3 second prime. When working, the pump just ran all the time, not just for 3 seconds.

Scott_ Anderson also said- "Have you checked for spark at the spark plugs when trying to start the bike. This can also give an indication of bad hall sensors if there is no spark"
We haven't checked plugs since replacement MCU motronic has been installed. We will check this though, thanks. We expect negative result though, given previous experience.

Scott said- "Have you checked for any motronic fault codes.

Don't want to assume the obvious, but just to confirm you are doing all this testing with the bike on the center stand and the side stand in the up position."
Not checked motronic fault codes yet. We will do this- it's on the list now. Yes, all relevant testing done with side stand up. Thanks for saying, easy mistake to make.

Scott_ Anderson said- "Like flybd5 is thinking, if you have a bad ground to the motronic, it's not going to work correctly."
When you say this, are you meaning the motronic relay? Or the motronic unit MCU? Further, if you mean the MCU motronic unit, do you mean the small spade connector on the outside of the MCU...? If you mean the motronic relay, as above, we will test this.

Flybd5 said- Also, did you check that you properly installed the ground strap to the Motronic grounding tab on the side of the unit? If I remember correctly, forgetting that, or not putting it correctly, also causes most of the symptoms that you are seeing. Make sure that the ground strap hasn't been damaged either.
Sure, thanks Fly, we'll check that one as well, I've just been taking it for granted that it's fine. I have been cleaning up the connector, but I didn't check continuity to earth. I'll add that to list.

Again, thanks all. We have stuff to check out here. Will get to it soon as we can and get back to you with results of checks. David (&Dad- Danny) PS bear with me please, trying to get formatting and stuff right using a phone ain't easy, lol!

If you think I'm still missing something, please let me know.

Flying Duck · Posted: Mon Jun 22, 2020 3:39 pm Post subject:

bikerdavy · Posted: Mon Jun 22, 2020 4:37 pm Post subject:

Duck,
Ah right. Maybe we were mistaken there, just talked with Dad and we were given what seems to be a wrong wiring diagram for that. That's on my list to check as well, then- where motronic relay pin 85 comes from.

Are you able to give us a link to the wiring diagram you got that from? It's far better and more comprehensive and helpful than the Clymer one we have.

Flying Duck · Posted: Mon Jun 22, 2020 5:14 pm Post subject:

Here's a link to a PDF. It's for an LT but the wiring of the RS is the same. The LT just has some additional circuits for the radio and electric windscreen.

http://dws.x10host.com/xfer/1994.K1100LT.Wiring.SLP.Final.pdf

Note that this is for model year 94 and later K1100s. The 93 and earlier K1100s use an earlier Motronic version and ABS system.

Clymer wiring diagrams, Laughing

_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

bikerdavy · Posted: Tue Jun 23, 2020 7:28 am Post subject:

Flying Duck · Posted: Tue Jun 23, 2020 8:17 am Post subject:

Motronic pin ID: You can cut the zip-tie that holds the back cover onto the Motronic connector. Once you remove that back cover you can tell which pin is which by the wiring colors. (The pin numbers might be molded into the plastic too but I'm not sure about that since I haven't opened one up in a while.)

BMW sells these wiring diagrams on CD: ($50 each)

06727694500 - SLP - has wiring diagrams for all BMW bikes from 74-93

01797720399 - SLP 2 - has wiring diagrams for 93-08

That's just the basic underlying B&W diagrams of the PDF I linked though. I then take the images and add Engrish labels to the diagrams in Powerpoint to make them easier to read without having to look up the the coded name for each component.

Here's a color-coded one page wiring diagram for K100s. This is for the early (83-85) models but the only material difference for 86+ models is that the fuel tank connector is different:

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/kwiring/Early%20K75%20K100/K100_Early_Wiring_Diagram.jpeg
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

bikerdavy · Posted: Tue Jun 23, 2020 4:30 pm Post subject:

Gentlemen! We have success! Thanks very much to all who have helped!

In the end, it was the motronic relay that was the problem. As i say, we had checked this before, but we recently got the replacement motronic unit and it was behaving just like the old one. We had not yet competed all checks again on this replacement motronic unit.

We tried the old motronic unit again, and it is definitely dead. No priming of fuel system on turning key.

The question now is, what blew the previous motronic unit(s) and moronic unit relays?
The most likely explanation (and the one we're hoping is true) is that the fault was caused by using a cheap battery charger on the bike whilst the battery was connected in situ in the bike. I'll be riding with caution for a while, and carrying spare relays and probably a spare motronic as well.

If you want to, here is the 2 minute video of Dad and I showing the problem getting fixed. Many thanks again! This has been a long time coming, and has involved a lot more replacing things and checks than I've discussed here!

https://youtu.be/CqXgN-76DH4

PS: my long- suffering mother says she's also glad it's fixed, but wonders if we will be a bit disappointed now we will have nothing to do. She is quite sure that we will be talking about this for years to come, though. Laughing

Flying Duck · Posted: Tue Jun 23, 2020 4:38 pm Post subject:

I can't see a battery charger frying a Motronic unless the bike is turned on and the charger is putting out much higher voltage than the regulated 14.2V that the alternator puts out.

Glad to hear that you got things sorted out. Beemered

_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE