BMW K bikes (Bricks)


You are not connected. Please login or register

View previous topic View next topic Go down  Message [Page 1 of 1]


1Back to top Go down   Intermittent fault on K100 Empty Intermittent fault on K100 Sun Apr 07, 2024 3:14 pm

walker452

walker452
New member
New member
My recently acquired 1986 K100 ‘project’ has been giving me the runaround since we met.  It seems every time I get her booked in for an MoT she refuses to start, despite running well the day before. 

Finally managed to get down to the test station yesterday for the old girl’s first MoT in three years and very proud to say (and relieved!) that she passed with flying colours!  So now I know she’s a keeper I want to understand this starting issue.  I finally got the bike going yesterday after I disconnected/reconnected the connector block on the black cable which connects into the computer and is routed down the RHS front fork leg. The symptoms are that the pump delivers good pressure to the fuel rail but the plugs are still dry after cranking the motor. There is a  healthy looking spark at all four  cylinders too. I found the link below on this forum and the troubleshooting used seems relevant to the issue I have, but it’s not clear how this ever got resolved. 

The bike has restarted OK since yesterday, but having not really identified a root cause for the problem I’m not confident I won’t get stranded somewhere in the future.  

Just wondering if anyone on this fantastic group has any strong views or pearls of wisdom regarding this apparently random starting issue?
My recently acquired 1986 K100 ‘project’ has been giving me the runaround since we met.  It seems every time I get her booked in for an MoT she refuses to start, despite running well the day before. 

Finally managed to get down to the test station yesterday for the old girl’s first MoT in three years and very proud to say (and relieved!) that she passed with flying colours!  So now I know she’s a keeper I want to understand this starting issue.  I finally got the bike going yesterday after I disconnected/reconnected the connector block on the black cable which connects into the computer and is routed down the RHS front fork leg. The symptoms are that the pump delivers good pressure to the fuel rail but the plugs are still dry after cranking the motor. There is a  healthy looking spark at all four  cylinders too. I found the link below on this forum and the troubleshooting used seems relevant to the issue I have, but it’s not clear how this ever got resolved. 

https://www.k100-forum.com/t1686-fuel-pump-not-powering-up?fbclid=IwAR2K6SOvpbFHVciZEHEbMgmoiZnGyf0jyay9UglkqWzGHNPSnU_-V1XBJz4_aem_AUUNGuY27S97Ct7xAOH3NPv9yAFCdUhFZtWbB3PQcYWHHepiCwKV45gRQ-ovd8s_3Fc#lupxuziujoeuna35ro

The bike has restarted OK since yesterday, but having not really identified a root cause for the problem I’m not confident I won’t get stranded somewhere in the future.  
 
Any thoughts please?

    

2Back to top Go down   Intermittent fault on K100 Empty Re: Intermittent fault on K100 Sun Apr 07, 2024 4:53 pm

duck

duck
Life time member
Life time member
Remove the connector for the L-Jetronic under the seat and inspect the terminals for corrosion.

Sometimes just disconnecting and reseating that connector solidly helps.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

3Back to top Go down   Intermittent fault on K100 Empty Re: Intermittent fault on K100 Sun Apr 07, 2024 4:57 pm

walker452

walker452
New member
New member
Thank you, I shall investigate this. 😊

    

4Back to top Go down   Intermittent fault on K100 Empty Re: Intermittent fault on K100 Mon Apr 08, 2024 7:27 am

Born Again Eccentric

Born Again Eccentric
Life time member
Life time member
“ I disconnected/reconnected the connector block on the black cable which connects into the computer and is routed down the RHS front fork leg”

Not sure what cable this description refers to - the routed down the rhs fork is a bit confusing…maybe you are talking about the top section of the fork only? The only wire that routes down my rhs fork is for the abs sensor…and judging by your photo in your introduction post, you don’t have abs.


A lot of intermittent problems are caused by dirty/loose earth connections. Definitely worth your time (and peace of mind) to get a can of electrical contact cleaner (deoxit is best but pricey and seems to only available on line in the UK) and give the all the connectors and good squirt and disconnect & clean the main earth point (bolt on centre frame under the fuel tank on left hand side) and the earth connection to the gearbox housing (left hand side below and just behind the coil cover). 


__________________________________________________
Intermittent fault on K100 Uk-log10 Intermittent fault on K100 Sco-lo15
                              Paul  Intermittent fault on K100 905546712

"Heidi" K100LT 1991 (Grey) (VIN 0190172 Engine No. 104EB 2590 2213) - 5th owner. January 2014 (34,000 - 82,818 miles and counting....)
"Gretel" K100LT 1989 (Silver Grey) (VIN 0177324 Engine No. 104EA 2789 2211) - 4th+ owner. September 2015 (82,684 miles and counting....). Cat C Insurance write-off rebuild Feb 17
"Donor" K100LT 1990 (Red)  (VIN 0178091 Engine gone to Dai) - 6th & final owner (crash write-off now donor bike).   June 2012 (73,000 miles) to November 2013 (89,500 miles)
    

5Back to top Go down   Intermittent fault on K100 Empty Intermittent problem Tue Apr 09, 2024 12:22 am

daveyson

daveyson
Life time member
Life time member
Two thoughts.

1
Have you ever noticed that bricks are like horses? If you fear something (MoT) they can sense it, and won't start, or try to buck you off. Never fear (Have you ever noticed that my avatar has two iron horses? One is made with horse shoes)

2
An intermittent problem is the most annoying problem you could have. And they wonder why a bloke grabs a gun, goes down to Macca's, and starts shooting people. But better to make it a constant problem, then fix it.

Fuel at the fuel rail, but dry cylinders makes you think the injectors aren't opening. If the injectors aren't getting power, they won't open. If they're not getting earth, they won't open. Wiggle the loom from the injectors here and there to see if that reproduces the problem, or eliminates it. I'll guess they're not getting earth, but testing with a computer safe test light will reveal what's missing.


__________________________________________________
11/1985 BMW K100RT (late model)  Vin. 0090567
 ~120,000 km
    

6Back to top Go down   Intermittent fault on K100 Empty Re: Intermittent fault on K100 Sat Apr 20, 2024 1:25 am

jjefferies

jjefferies
Life time member
Life time member
duck wrote:Remove the connector for the L-Jetronic under the seat and inspect the terminals for corrosion.

Sometimes just disconnecting and reseating that connector solidly helps.
At one point Red was stopping intermittently on the freeway. I found that disconnecting and reconnecting the connector, reasonably easily done as these things go, would get the bike restarted. So thinking it was obviously electrical I fell back on a crude fix. I took a needle nose pliars and rotated each of the spade connectors in the  L-Jetronic box by 3-4 degrees. Just barely twisting them. This  ended the problem till I got back home from that ride and I could go in and clean them all. And that eliminated the problem. Well I've not had it come back in the same way.



Last edited by jjefferies on Sat Apr 20, 2024 1:36 pm; edited 1 time in total (Reason for editing : Improving the writing.)

    

7Back to top Go down   Intermittent fault on K100 Empty Re: Intermittent fault on K100 Sat Apr 20, 2024 1:02 pm

moriarti

moriarti
Life time member
Life time member
Ignition Control Unit is a possible cause, if you have not identified anything else, My intermittent fault was down to a faulty unit, good luck and enjoy your K.


__________________________________________________
1984 k100 rs red/black VIN  0004449 Now sold to Olaf
    

Sponsored content


    

View previous topic View next topic Back to top  Message [Page 1 of 1]

Permissions in this forum:
You cannot reply to topics in this forum