Hi!

I know, I know. One more topic with same problem. I have seen them all, but haven't had luck fixing the problem in the last month. Problem might lie there, as I am not competent with electronics, but trying my best.

One morning bike stalled after few minutes of riding when I was stopped, no problem, started back right away. At the afternoon I was riding 80km/h when bike suddenly stopped. Started to fire her up and worked ok for a short while and stalled again. Situation is the same now, works ok for 5-10min (even thought little rich I think) to a point that it stalls right away, no hiccups, just stalls. After stalling need to cool down and then starts ok again. I was very sure it was HALL-sensor and changed it, but no luck. 

Here is a link to video with stalling:

https://drive.google.com/file/d/1V4ERUBVMhtCjWiclf4ll9fxi_Nk3jwI4/view?usp=sharing 

I have used Bert's troubleshooting guide and values there.

Things I have done now: 

• Fuel pressure from before injectors and after them: Ok, ~35psi.
  
• Fresh fuel changed.
  
• New fuel filter.
  
• New crank breather z-tube.
  
• All grounds checked & cleaned.
  
• Voltage regulator changed to new one.
  
• HALL -sensor : Chanced to new Q-tech sensor.
  
• EFI computer tested with another one, no effect.
  
• Plugs: Changed to new ones.
  
• Injectors : Changed seals. Right voltage to injestors.
  
• Coolant thermal plug: Metered from it's plug, giving right values.
  
• Rough engine when throttle position sensor off.
  
• Not able to find any leaks.
  
• Not able to found any broken wires.
  
• 5&6 fuses changed.
  
• Vacuum switch disconnected, no effect.
  
• Air flow meter readings:
  PIN 7-5: 93,3
  PIN 7-8: 350,7
  PIN 8-5: 361,1
  PIN 8-9: 191,5
  

I rode bike around 200km after keeping her in warehouse for winter, worked fine before all this.

What am I missing?

Thanks on advance 

You don't mention ICU and early ones do occasionally go faulty and cause that.

Coils were a problem on the early models as well.

Like Point-Seven-five has indicated, checking coil resistance according to the troubleshooting guide would be in order. Also,  consider inspecting the fuel filter screen or sock for clogging, replacing the fuel filter if you don't know its age, inspecting the four-pin plug located under the fuel tank that supplies current to the pump via the fuel level sender, and checking continuity through the plug to the pump.

I have 2 early Ks and that tank plug [front left] has been an issue on both. I have resolved it but it did kick in at random. 

I mentioned the ICU unit and early ones have a moisture ingress/condensation issue, some changed out on warranty. 

I have had coil fails too.

One thing that nearly drove a friend mad turned out to be the plug into the FICU unit under the seat. An intermittent cut out exactly like you describe. I have had that one too, incorrect seating of the plug. Unit itself can be perfect but the connection faulty.

Thank you gentlemen of your replies.

I measured coils today, both were as they should. Anyway I ordered used ones with orange towers to keep K on the road. 

Also checked FICU box connector on bike side and cleaned it. Opened also ICU to see if there is something wrong. 



Cannot tear it apart so don't know if those were problem. Re-soldered them anyway. Also ordered spare one. 

Still same problem

EDIT: Checked coils after problem occurred. 10,5kohm / 3.0ohm, 11,5kohm / 3.1ohm. Is it ok when hot?

Djsfh wrote:I rode bike around 200km after keeping her in warehouse for winter, worked fine before all this.
What am I missing?

Past performance is no guarantee of future results. 

If you haven't already, you might consider disassembling the ignition switch to check the condition of its contacts and mechanism. The condition of its plug connection to the wire harness beneath the tank can also be a source of intermittent problems

Laitch wrote:

Djsfh wrote:I rode bike around 200km after keeping her in warehouse for winter, worked fine before all this.
What am I missing?

Past performance is no guarantee of future results. 

If you haven't already, you might consider disassembling the ignition switch to check the condition of its contacts and mechanism. The condition of its plug connection to the wire harness beneath the tank can also be a source of intermittent problems

Thanks, will check this too. I changed fork springs during the winter so it is always possible that it had come loose.

Djsfh wrote:

Laitch wrote:

Djsfh wrote:I rode bike around 200km after keeping her in warehouse for winter, worked fine before all this.
What am I missing?

Past performance is no guarantee of future results. 

If you haven't already, you might consider disassembling the ignition switch to check the condition of its contacts and mechanism. The condition of its plug connection to the wire harness beneath the tank can also be a source of intermittent problems

Thanks, will check this too. I changed fork springs during the winter so it is always possible that it had come loose.

That's a possible cause......

I agree that the ignition switch could be at fault here. It's 37 years old and probably has never been cleaned.

Now that I think about it, your symptoms are very similar to what mine are when the ignition switch on my '92 K75RT acts up and needs to be cleaned.

I had a similar situation, while waiting for tow truck...I lifted the rear of the tank, and pulled out the fuel relay, it was warm to the touch. I popped the cover off, all looked ok, gave it a tap on the ground, put the cover back on, popped the relay back in, pressed the starter, success... cancelled the tow truck. Rode home, bike is now behaving. New relay ordered so I'll carry a spare.

On todays schedule was ignition switch maintenance and testing replacement ecu. Same symptoms continues.

Realized, that I didn’t tell here, that after it stalls it still cranks, but it won’t fire up

Also pulled fuel pump off, the screen wasn’t very clogged. There were some rubber pieces and some dirt on the tank. Waiting for replacement pump.

Maybe leave the fuel pressure gauge on, see if the pressure drops causing the stall. 

Check that the instrument cluster lights are working as they should. 

Maybe the coils were good when testing but not good under load.

Missing 2 things, not electrical related.

Is the retour valve in the tank still working as should be?
Should be not too much pressure blowing through.
Number 19 in the drawing;
https://www.realoem.com/bmw/en/showparts?id=0501-EUR-06-1983-K589-BMW-K_100_83_0501,0511_&diagId=16_0815

And is the tank cap taking vacuum?
When the bike stalls, open the cap, should start right away.
If not, it's not the cap.

Also, that is electrical, possible, te solderings on the printboard of 1 of the computers are gone bad.
That goes for the ICU under the tank, and ECU under the seat.

Check your exhaust valve clearances. You could find they're tight. Valve clearances tighten as the engine warms up to operating temp. If they're on the limit, a little heat and they start not closing and the engine stalls. Had this happen to me twice. Once a few years ago with my K100RT and also back in 1975 when I was driving across Australia in a bomb car. Crazy thing to do I know, but I was only 19. Luckily I had the presence of mind to work it out and to also have a set of feeler gauges in my kit.

Please enlighten some of us as to what is a "bomb car".
Thanks
Shep

Shep wrote:Please enlighten some of us as to what is a "bomb car".
Thanks
Shep

LOL... A 'bomb' is an old car in need of repair. Must be an Aussie term. She was an old '61 Wolsley I bought for 50 bucks to make the 4,000km trip back home.

Holister wrote:LOL... A 'bomb' is an old car in need of repair. Must be an Aussie term. 

Where I live, they're known as beaters.

Thanks guys! Will check those things also.

Had to take back a bit yesterday. After ignition switch cleaning on thursday it worked like a charm. Yesterday, nothing. Don't know if it is due that or did I do something else, since I also give fuel pump little time out of the tank. Let's see.

Must admit that I felt stupid yesterday checking what is wrong with ignition lock. Soldered it off....Before noticing that I had disconnected it under tank when adding bar pad. Well you always learn.

Checked valves, one exhaust was little bit off being 0,20-0,25. Two inlets 0,10-0,15 and 0,05 - 0,10. Will change shimms to correct that tomorrow.

daveyson wrote:Maybe leave the fuel pressure gauge on, see if the pressure drops causing the stall. 

Check that the instrument cluster lights are working as they should. 

Maybe the coils were good when testing but not good under load.

Left, not dropping when it stalls. I think cluster lights is working as they should.

Sooo.....

Didn’t adjust the valves, because it wasn’t so easy to found 29mm shims. Ordered them but I bet the problem is not that, two valves were 0,05 and 0,10 off.

More things checked&done:

-Immediatly after it stalls, there is spark on every plug. 
-Coils changed to orange headed ones.
-fuel pump changed to new one.
-all ext, fuel lines replaced.
-flushed coolant.
-after stalling, plugs are dry.

I can’t find any bad wires, but wiring has been fixes earlier I think. Some of the wiring has been replaced earlier and there has been used quite much hockey tape or something like that.

There is quite much of noise from the tank, I guess it is from return fuel line valve. Have to get rid of that.

So, could it he that injectors stops at the same time for X reason? There should be spark, air and fuel.

Djsfh wrote:So, could it he that injectors stops at the same time for X reason? There should be spark, air and fuel.

Clymer manual (Chapter 7, page 226 in second edition) contain a drawing and description of fuel injection system. If you have spark, the Ignition control unit (ICU) should be ok, but there could be something wrong in connection to fuel injection control unit (FICU). According to description there is one direct line between units and other connection passing through the injection relay to the gas pump and the FICU. Note, there are wiring diagrams at the end of the book. They can useful in hunting a fault.

If you need that manual, just send me a pm.

If it stalls when wiggling the wiring, especially where the alterations were made, that would be worth a closer look.

It’s working!

Don’t know if I feel bit dull, angry or pissed off 

I changed Hall as a first thing to new, high quality one since symptons was just like it being bad. Well, decided yesterday to test that sensorwith hairdryer method. Not working! Seems that the part I bought was DOA. Luckily I found one sensor from old owner leftovers and it was working 

It was quite much money and time spend, but after all that she runs much better than before.

Thanks for everyone participating And giving help 

Djsfh wrote:It’s working!

Don’t know if I feel bit dull, angry or pissed off 

I changed Hall as a first thing to new, high quality one . . .  Not working! Seems that the part I bought was DOA. 

Will you be trying for a full refund under Q-Tech's three-year warranty, or did you already receive one?

Laitch wrote:

Djsfh wrote:It’s working!

Don’t know if I feel bit dull, angry or pissed off 

I changed Hall as a first thing to new, high quality one . . .  Not working! Seems that the part I bought was DOA. 

Will you be trying for a full refund under Q-Tech's three-year warranty, or did you already receive one?

Yeah, I think that would be fair, let’s see what Rudolf will say about this . It is quite expensive part to just keep in stock if I would be refunded with new one.