BMW K bikes (Bricks)

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lhead71

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The bike has been running fine, starts and runs fine for two weeks now. That is the length of time I have had it. I ride almost every day.
Today I tried to start it and placed the choke on, turned the ignition on(everything lit up fine), and hit the starter button. The fuel pump turned on( I could hear it in the tank),
and the starter tried to turn the engine over but it would not start. I tried for a good 10 minutes.
Then something funny happened, The starter kept turning over even after I took my thumb off the button. I hit the kill switch and it was still turning over, I flipped the ignition key off and it still turned over for a good 30 seconds before it stopped on its own.
I just cant seem to get the bike started, out of the blue. Ideas please? Thank you.

    

Crazy Frog

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I cannot tell you why the bike was not starting, but the reason why the starter is turning on its own is because of the contact of the starter relay welded together.
After 10 min trying to start, your battery was weak and you didn't have enough voltage to run the starter.

CF


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Bike won't start after running fine for two weeks Frog15Bike won't start after running fine for two weeks Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

charlie99

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some folks have found that a "flooding" event has happened ihead

pull one of the plugs to confirm this .
if so ...pull them all and dry them out in the first instance .

from what i have read it seems to be unexplained at this point on our bmws .
but i would be checking the connections to the under seat computer , the hall sensors connection under the tank and the ignition computer under the tank also ...use deoxit to clean up the connections .

you may need to clean up the contacts on the starter relay with a points file .dont use anything that might leave particles/granules behind ...like wet and dry or sandpaper ...although many just replace it .

im not sure of the start up process but it may go a little like this ....
i suspect that durring the first few hundred milliseconds the injectors just open till the ignition computer gets a few pulses from the hall effect devices ,firing the plugs, then the efi computer pulses the injectors as usual as it sees a rate change.
thus my thinking of cleaning the connections to the hall sensors and relevant computer bits .
i have seen this type of start process on a few cars and it doesnt seem strange to me

when i finally get around to redoing my throttle body rubbers and injector seals i intend to prove this whilst the injectors are still free

    

Crazy Frog

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@charlie99 wrote:im not sure of the start up process but it may go a little like this ....

Hey Charlie and lhead71,

Have you seen the following?

The starter relay and Fuel Injection relay close, Hall sensors get power.
The FI relay energizes (+) the fuel pump, the idle switch, the injectors and the air flow meter.
The Jetronic receives (pin #4) the signal that the engine is starting and it sets itself on starting mode (enriching the air/fuel mixture)
Electronic ignition module pin # 9-10-14 send power to the ignition coil
Electronic ignition module pin #8 send engine rpm info to pin #1 of FI computer
Electronic ignition module pin #7 send ground to the coil of the FI relay as soon as the starter switch is depressed. The ground will stay on after the starter switch is released as long as the Electronic ignition module receives a signal from the Hall sensors.

This is here on this starting troubleshooting page with a lot more information that will be valuable to find why the bike is not starting.

CF


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Bike won't start after running fine for two weeks Frog15Bike won't start after running fine for two weeks Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

charlie99

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great information page bert ....thanks


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OBike won't start after running fine for two weeks Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

lhead71

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Checked the starter and it is working fine, the battery is recharged at 12.5 volts, pulled the plugs and they were not wet at all, turned it over with a plug out and there is plenty of spark. I am guessing it is a fuel problem. Can a fuel pump die just like that? I am going to change the fuel filter, but I am unsure how to check the fuel pump and regulator are working.

    

pjjms

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Put your ear on the fuel tank while trying to start it. Your will clearly hear the pump running at the same time the starter is turning over and for a 1/2 second or so after the starter button is released.

    

charlie99

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i guess you could always pull the high presure line at the fuel rail ...near the injectors ...or at least loosen the clip and see if there is presure there .


but maybe work through crazy frogs (berts) link to diagnosing start issues !!!
but mine died whilst in transit ...one minute it was good ...next ...dead as a dodo .....the breather line to the fine mesh filter at the bottom of the pump had colapsed and i suspect rubber entered the fuel pump siezing it .....

i had recently been using ethanol laced fuel which is different than i usually use ....may have been a contributing factor ..
but ended up replacing the fuel pump ....since its been a dream .....(also replaced all the fuel lines through out )

interestingly i rode mine for a few weeks after purchasing it ....after a few months of "no use" by the previous owner

    

Albyalbatross1

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I too had the starter relay problem. Opened her up and cleaned it. All was then good. However I also had a recent problem of with a Green Frog. Long story short, the water temp sensor was not connected properly. This was stoppingbbike from starting. (learnt a lot from berts flow chart).

    

Comberjohn

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That seems to be exactly how the fuel pump dies.
As pjjms said, hit the starter and listen for the fuel pump whirring. If you don't hear anything then its most likely the pump. It is worth checking the 4 pin connector that powers the pump as well. Its not unknown for it to have become disconnected or have corrosion problems.
My K started after sitting for a couple on months, drove for two miles then packed up. Just in the process of stripping the pump down to see if it can be saved.
If you are parking the bike up for any length of time make sure there is enough petrol in the tank to keep the pump submerged. I blame that on my pump's demise as it was well into reserve when I parked it up and the petrol acts as a lubricant.
If the pump is whirring, then check the fuel filter. You should be able to easily blow through it.
The only time my K broke down on me was because I had never changed the filter and it completely blocked. (Red face!)
Some of us have had problems with Ethanol being added to petrol and breaking down the rubber parts in the tank, blocking filters and jamming pumps.
Fortunately, checking the pump and filters is an easy, if fiddly job.
Think of this as your baptism of fire. They are reliable, honest!

http://www.johnsdrivingschool.co
    

IPJ100

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Hi there, when your starter was whirring around, did it sound as if it was actually cranking the engine over? if your bike has been sat about a while before you got it then the starter sprag clutch may have become partly siezed or dry of oil. They will then work afew times and then stop. If it was cranking the engine over then you would have high current through the starter relay and as crazy frog said probably arced them closed, or it could just be a gremlin got in. if it is the starter clutch then get the kettle on and be prepaired to remove the back end off your bike, hope its just a relay.

Ian


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I still haven't started restoring my C90. damm it Bike won't start after running fine for two weeks 652573
    

Comberjohn

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Hi Ian. Don't scare him! Think he said in an earlier post that he was getting a spark so the engine must be turning over.

http://www.johnsdrivingschool.co
    

IPJ100

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Ah yes - so he did, sorry. Were bikers, we dont scare that easy do we? hang on the missus is coming, must sign off now se you later and good luck!!


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I still haven't started restoring my C90. damm it Bike won't start after running fine for two weeks 652573
    

charlie99

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verry definatly check the 4 pole connector .....below the tank at the back accesable by removing the right side cover...kinda sits between the starter and the batery ....often found to be an issue .


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OBike won't start after running fine for two weeks Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

lhead71

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So I found out that the former owner who did ride it often, had not changed the filter. I went and got a new filter and replaced it. The pump is working( I can hear it humming when I touch the starter, there is pressure in the fuel line, I checked the pressure with a PSI Indicator dial directly attached to the fuel tank - When I turned the bike over it built pressure well past 100 PSI. I don't know if that tells me anything. I followed Bert's chart but I can't seem to find the problem. I appreciate all the responses. I wish I had more time to work on it but I have a young daughter who needs my attention more than my bike. I am just about ready to bring it to the dealer and have them tell me what's wrong.

    

Comberjohn

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Was the pump whirring before you changed the filter?
Process of elimination doncha know.

http://www.johnsdrivingschool.co
    

ReneZ

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Charlie99, on the earlier bikes (and I think that includes the OP's bike) that connector sits between both tank hose connections on the left front.

100 PSI is way too much. Something must be blocking the line. The Fuel Pressure Regulator normally keeps the pressure on 2.5 Bar (36 PSI). If the line is blocked there is an internal safety in the pump that normally opens between 4 to 6 Bar (58-87 PSI). If you achieve 100 PSI something is definitely wrong.



Last edited by ReneZ on Fri May 13, 2011 7:16 pm; edited 1 time in total


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Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029) Bike won't start after running fine for two weeks Rain
BMW K1200GT - 2003 (ZK01223)
    

charlie99

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oh !.....thanks rene
but it seems that ihead has got presure and spark after all
i guess the next step is the fi relay and injector action ?



Last edited by charlie99 on Fri May 13, 2011 7:27 pm; edited 3 times in total

    

ReneZ

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Sorry, messages crossed in cyberspace :-)


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Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029) Bike won't start after running fine for two weeks Rain
BMW K1200GT - 2003 (ZK01223)
    

lhead71

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So I measured the fuel pressure by splicing in the regulator between the tank and fuel rail and it was perfect at 36psi.

    

Crazy Frog

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You are progressing and you're on the way to recovery.
You get fuel pressure, you get spark, but, do you get power (+12v) at the injectors (red/green wire)?

Here is another common problem (I got it before): Have you checked the connection of the FI computer (under the tool box)? remove the connection and push it in again.

Also, pull all the fuses one after the others, check them with an Ohmmeter and reseat them properly.

We'll help you and you'll get more time to spend with your little girl cheers


__________________________________________________
Bike won't start after running fine for two weeks Frog15Bike won't start after running fine for two weeks Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

ReneZ

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The connector of the ECU has to 'click' home. There's a pin at the opposite site of the hook on the connector that should be pushed into a catch. There's a little hole in the tool tray that is there to allow you to push the catch back if you want to disconnect. Have a good look (after cleaning the plug/ECU connections) if it engages.
Easiest (and most dangerous!) way to check the injectors is to take the rail, with injectors attached, out and see what it does. Make sure you put a rag over the holes so there is NO WAY some petrol can meet a spark. It shouldn't happen, but.... There are a few 'movies' on YouTube that can show you what you can expect to see.
Have a look if fuel gets past the regulator. We had a case where the pump could bring up the pressure (just), but there was not enough flow. The return line to the tank was not passing any fuel.

No worries, we'll get there!

CF, love your last remark!!


__________________________________________________
Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029) Bike won't start after running fine for two weeks Rain
BMW K1200GT - 2003 (ZK01223)
    

chrish8846

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I had a problem with a intermittant start on my K100 and had already cleaned all the connectors on everything,under seat computer and the FI controller under the tank included. One morning when it would not start again I did a Honda trick that I learned years ago at a Honda tech school. I twisted the pin connectors slightly on the computer(this only works on flat connectors) about 5-10 degrees and put some dielectric grease on the connector and reinstalled the connector making sure it seated fully. It has started instantly since.

    

lhead71

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Thank you to all who have helped diagnose the problem, especially to Bert. After using his flow sheet, realizing I had spark, fuel pump was working, and battery was charged, I checked the connector under the tool box that controls power to the injectors and sure enough that was it.
Somehow it had loosened up and I was able to take it off and then re-secure it tightly. Hit the starter and bingo, running great! Power back to the injectors. ALl this did give me the opportunity to see how the bike comes apart and here things are, as well as do some maintenance, like replacing the fuel filter. Looking forward to having it back on the road.

Thanks guys!
Lew

    

Crazy Frog

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We start to be good cyber mechanics. Bike won't start after running fine for two weeks 212902


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Bike won't start after running fine for two weeks Frog15Bike won't start after running fine for two weeks Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

charlie99

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yay ....good work ihead .....happy riding to you


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OBike won't start after running fine for two weeks Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

Comberjohn

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Good news Lew.
I hate it when my bike is not running properly.

http://www.johnsdrivingschool.co
    

sidecar paul

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Well done Lew

It's always a good idea to apply pressure to the back of the injector control box when refitting the plug. The rubber mountings are very flexible. You should hear a definite click when the connector is correctly in place.

Paul


__________________________________________________
'84 K100RS (0014643) (owned since '85), 86 K100RS (0018891) with Martello sidecar (built as an outfit in '88),
'51 Vincent (since '67),'72 Montesa Cota (from new), '87 Honda RS125R NF4 (bought 2015) 
....No CARS never ever!
    

charlie99

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good to have you running again ......another "k" bike back on the road

good work all !!!!!


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OBike won't start after running fine for two weeks Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

K-BIKE

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Well done great job.
Regards,
K-BIKE

    

nutheastah

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[quote="Crazy Frog"]
@charlie99 wrote:im not sure of the start up process but it may go a little like this ....

Hey Charlie and lhead71,

Have you seen the following?

The starter relay and Fuel Injection relay close, Hall sensors get power.
The FI relay energizes (+) the fuel pump, the idle switch, the injectors and the air flow meter.
The Jetronic receives (pin #4) the signal that the engine is starting and it sets itself on starting mode (enriching the air/fuel mixture)
Electronic ignition module pin # 9-10-14 send power to the ignition coil
Electronic ignition module pin #8 send engine rpm info to pin #1 of FI computer
Electronic ignition module pin #7 send ground to the coil of the FI relay as soon as the starter switch is depressed. The ground will stay on after the starter switch is released as long as the Electronic ignition module receives a signal from the Hall sensors.

This is here on this starting troubleshooting page with a lot more information that will be valuable to find why the bike is not starting.

CF[ Illigitumus non carborundum ] Many thanks , been looking for this info for months, maybe I'll get to ride this summer after all

    

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