BMW K bikes (Bricks)

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1Back to top Go down   Ignition Issue Empty Ignition Issue Fri Apr 29, 2016 1:02 pm

Grizzly

Grizzly
Silver member
Silver member
Working on an early K100 just now which has an interesting problem.

The engine will only run (and rough as it is) while the starter button is pressed. As soon as it is released the power dies and then it cuts out after a couple of seconds.

Any ideas what could be causing this?


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Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

2Back to top Go down   Ignition Issue Empty Re: Ignition Issue Fri Apr 29, 2016 3:52 pm

92KK 84WW Olaf

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Life time member
Life time member
Check out the connection of the Fuel Injection Control unit under the seat. The plug connector to it can become dislodged, also the pins may need cleaning. Is easy to get out. Be careful removing it as there is a clip to be moved to free the plug. As you look from the left side after removing the side cover you will see the plug and the silver unit. There  may/should be a 'pin' behind the right hand side cover to hold it in place....odds are that's not there. The whole under seat tray will lift up for you with a little wriggle.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

3Back to top Go down   Ignition Issue Empty Re: Ignition Issue Fri Apr 29, 2016 3:59 pm

Grizzly

Grizzly
Silver member
Silver member
Already checked that Okay with no joy. Used a well known working one and there was no difference.

Should have said also that fuse number six is only powered up whilst the start button is pressed too. On my bike (being only one year younger than this problem one) that fuse has no power before the engine is started, but then stays live while it is running. Is this extra info any help?


__________________________________________________
Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

4Back to top Go down   Ignition Issue Empty Re: Ignition Issue Fri Apr 29, 2016 4:11 pm

92KK 84WW Olaf

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Life time member
Life time member
I am not so good with electrics, but the thing is you have got power to fuel pump etc if all is turning over. With what I have picked up on the forum pressing the start button powers up the fuel pump etc only for as long as is needed for the engine to be turning over and start. Once its running then the Hall Effect Sensor provides the signal and that comes into the FICU under the seat. I have a friend over here who used to work in BMW and we have each time identified this as the problem.

If you are happy with the unit AND the quality of the loom wiring into the plug [as in no breaks in it] then not too sure where to go. The whole system works via earths and if they are not good strange things happen. There are also quite a few posts about starter motor brushes doing weird things like this too and its not much trouble to get at them.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

5Back to top Go down   Ignition Issue Empty Re: Ignition Issue Fri Apr 29, 2016 8:29 pm

RicK G

RicK G
admin
admin
When you press the start button an earth (ground) is extended to the fuel injection relay to make it operate. Once the engine starts the Ignition Control Unit ICU recieves a signal from the hall sensors and it then sends the earth to the fuel injection relay to keep the engine running after the start button is released. If the engine does not start the earth is kept on for 1.5 seconds after the start button is released.
The hall sensors are working because the engine fires and will keep running if the start button is held down.
The problem is most likely in the ICU or plug so, if you can, change the ICU for a known good unit and clean the pins on the plug. The ICU is under the front of the tank up against the steering head.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

6Back to top Go down   Ignition Issue Empty Re: Ignition Issue Fri Apr 29, 2016 9:10 pm

Holister

Holister
Life time member
Life time member
A check of the wiring schematics shows that All Roads Lead To Rome...... or in this case, the ICU. I think Rick will be spot on.:cyclops:
The ICU plug has a habit of coming loose because it's only held in place with the rubber cover. There have been a few problems relating to this. The contacts probably need a good clean with DeoxiT.


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1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Ignition Issue Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

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