The motor cranks fine but will not start. Then, I wait awhile (30 minutes or so) and try it and the motor starts right up. I need to keep the revs up until it gets warm or it will not idle. When it's warm, it idles fine and runs fine. I welcome any and all suggestions as to what to look for. Thanks, Dennis

hi dennis ...

what tecnique are you using durring the start proceedure ?

for me at least i use the choke lever to the second (wide open ) position for a few seconds ...as the engine starts .....then i let it relax to the second position (only half open ) for about a minute or so ,,,by then its usually warm enough to idle happily without the enrichment from the extra "choke " richening of the mixture

if i am starting whilst warm there is no need to get the choke action happening at all ....



hope this helps ...

Sounds like a fuel problem to me. Does the fuel pump start running when you press the start button and is there a good flow of fuel back to the tank from the return line. You should be able to see the flow when the tank is not full and there should be a very heavy stream of fuel. To test you can remove the filter and the line from the top of the pump can be directed back into the tank when the start button is pressed momentarilly. Don't let is squirt out of the tank it will pump almost a litre in a few seconds.
If you do get a good flow connect the filter and do it again and if the flow is reduced replace the filter.

Charlie, thanks, that sounds like my starting sequence and it works ok WHEN it fires up. Before this trouble started though, the motor would start on the first crank and would not need any "choke" to idle, except on very cold days.

Rick thanks. I'll check it out but the filter was replaced fairly recently so I'm not hopeful this will solve the problem.

This morning, it started and while I was holding the "choke" open, it put out a fair amount of white smoke which dissipated when the motor was warm and would idle on its own.

oh ? white smoke .... wow

dennisg844 wrote:
This morning, it started and while I was holding the "choke" open, it put out a fair amount of white smoke which dissipated when the motor was warm and would idle on its own.

Black smoke = mixture too rich
Blue smoke = burning oil
White smoke = too much air or ....steam

How's your coolant level? Any oil leak around the head gasket?
If you remove the coolant filing cap, do you see any tiny air bubbles when you try starting the bike?

Here are 2 ideas:
a) You have an very small coolant leak into your chambers. (Maybe taking an overnight to be significant)
When you try to start the bike you get a mixture of gas/coolant producing the white smoke. When the engine is warm (or after many tries), the coolant is gone. The leak may not exist when the engine is running (Aluminum expands when the engine warms up + pressure into the chambers).

b) You have water sitting at the bottom of the tank (common on these bikes as when it rain the water sits in the recessed area of the gas cap and goes into the tank when you open it)
At first start, your gas pump sucks some of the water, but after a fraction of second, because of the return line swishing the gas, the water is well mixed with the gas and you don't feel the effects.

What I would try:
Engine cold, remove the spark plugs and the connection to the fuel pump. Spin the starter for few second to empty your chambers.
Put everything back and try to start.

Just ideas...

CF

Fuel filter checks out ok. It's been starting ok, but needs some throttle to keep going until it's warm. Then it's fine. No more white smoke, just a puff or so. Coolant level is fine. No leaks anywhere.
I'm suspecting the coolant temperature sensor. It seems like the system thinks the motor is warm when it is not. Maybe the white smoke is from the mixture being too lean? I hate to just throw parts at it but I'll be installing a new sensor this week when I have some time. I'll let you all know what happens. If there are any other ideas out there, I'm open.

Before you changing the sensor, you could have a look in Bert`s troubleshooting guide at the portal.

There you would find a diagram with sensor values vs. temp.

Measure at connector 10 at the Jetronic multiconnector, and compare the results.

After a detour to solve what turned out to be a load shed relay problem, I'm back to this issue.
Some history: Occasionally, the engine would cut out for a split second while running at speed (60-70 mph; this could just be coincidence as I get up to speed shortly after leaving the house). The problem got worse as when it just would not start, but would start after some delay. Day before yesterday, the engine stopped dead at about the place where it would often cut out. It would not start. I towed it home. This morning, it fired right up. I got 200 yards from home and it died and will not start. It cranks fine and it puts out lots of fuel as I disconnected the fuel line to the injector rail and cranked the starter, a good stream of fuel.

Tomorrow, I plan to take out one spark plug, ground it to the engine case and if there's a nice strong blue spark, I'll figure it's a problem somewhere in the injector system. If there is anything other than a strong blue spark, I'll figure it's in the ignition system.

Does this sound like a good next step? All comments/ideas welcome; I'm anything but an experienced mechanic.

Dennis

p.s. I installed a new coolant temp sensor and deoxed the connections.

we have seen some weird throttle position sensors / switches faults ...could this be an issue ?

try disconnecting the tps completly ...funny plug with spring clip retainer ...and see if it dies again

i think there is an issue with the wof .(wide open throttle switch ....in some cases ...over richening the mix )

doesnt happen out here much ...but we have a vastly different atmosphere ..

It has not got the classic symptoms of a bad hall sensor but it would be worth a look and check it out. There is a PDF in the downloads section about it.

On older machines,( I have a dubious past involving old Triumphs) white smoke can sometimes be indicative of worn guides.
Silly question...but its not overheating is it? Or, its not the fuel vapour lock thing?

Sorry, lol, forget what I just wrote...I had my threads mixed up!

Saxon, no worries, I'm always mixed up.

I went to test the spark. Pulled #3 plug, grounded it against the engine case, got a blue/yellow spark. I'm not experienced in evaluating spark, but the Chilton book said look for a "fat blue spark". Thought I'd try another plug. Reinstalled #3 and pulled #2, pushed the starter button and the engine started right up!! Rough, of course, so reinstalled #2 and the thing ran perfectly. Coincidence, I thought.

Next day, it died as usual. This morning, it would not start so I thought maybe there is magic in the K100 world, so pulled the #2 plug and the darn thing started and now runs perfectly, with #2 reinstalled. Once might be coincidence, twice is a pattern?

Makes no sense to me but K100's don't follow any kind of logic I've ever studied!

I live near the Grand Canyon. If I didn't love this bike (and its sidecar) so much, I'd run (tow?) it up to the canyon and have a good push!

All ideas welcome.
Dennis

Do you got the genuine plug caps and wires?

And if, do you got the adaptors at the end of the spark plugs,
or it`s just the 4mm threads?

good point inge ...

The adapters are on the plugs. As far as genuine caps and wires, I don't know. These were on it when I got it 4 years ago. Would a bad cap/wire cause the motor to just quit?

the coils use a wasted spark system . that is they fire 2 plugs at the same time 1and 4, 2 and 3 , if there was a short on any one of the leads that whole coil pack could become ineffective ? same for a faulty plug or an open lead i guess .

So, I should:
1. Try to fine a short somewhere?
2. check for continuity in the spark plug wires?
3. try a new plug in #2?

Sound about right?

Appreciate the help.

The plug lead is bad or the furel is not on the top of the plug. If #3 wont spark then #2 won't either same for 1 & 4

check the high tension leads ...end for end ...should be over 2000 ohms but under 5000 ohms , could it be that just by mooving it some contunuity returns ...(.pretty common especially at the terminations )

Checked the continuity of all 4 spark plug wires. All were below 2000 Ohms (1400-1600). cleaned all terminals, used deoxit. Same problem: ran fine, then died, then would not start, then started and ran fine the next morning. I'll get to work on some of the other suggestions I haven't yet been able to get to.

I was just reading the new post from dewalque. His bike's issue is identical to mine, except for the starter (mine always turns but the bike won't start). There are some good ideas about possible causes in that thread.

I'll try the heat test on the hall sensor. Would a hair dryer set on "high" work ok?

One idea mentioned is that the bike might be sensing an overheat situation and shutting off the bike. Wouldn't the overheat light come on before the motor shut down? (I installed a new coolant temp sensor, cleaned and deoxed all the connections, with no change in symptoms).
I know the light works because it overheated due to the load shed relay being inoperable, and that relay shuts off the cooling fan when the starter operates. The light came on but the engine did not stop.

I've deoxed every connection I come across but haven't opened the ignition control unit. I'll do that.

I'm walking on very thing ice when I talk about electrics, but here goes: Could it be the fuel injection relay? I'm thinking that maybe when the bike heats up, a circuit either opens or closes, cutting off fuel flow. Would the relay act like this if it's going bad? Crazy idea?

thanks in advance for all answers/comments. This forum is great.

dennisg844 wrote:I'll try the heat test on the hall sensor. Would a hair dryer set on "high" work ok?

It would do the work, remove the small cover.

dennisg844 wrote:One idea mentioned is that the bike might be sensing an overheat situation and shutting off the bike. Wouldn't the overheat light come on before the motor shut down?

Depends,....it`s a dual sensor.......one element for the fan and warning light.....the other for the L-jetronic (and overheat protection).
If you got a short to ground in the last mentioned circuit, you won`t get any warning signals shown in the first.

maybe i am not that experienced but as far as i know bad hall sensors can give such effects - engine gets warm - no spark, engine cold - good spark. check that first i would say.

all the things with spark plugs, temp sensors etc would give you problems with engine running but it would not be dying so immediately.

that's what i think.

good luck!

I did the hall sensor test by taking off the cover, running the motor, heating up the sensor with a hair dryer for a full 10 minutes. No change.

Motor ran fine yesterday. Went to start it this morning and it will not start. Cranks fine but not even a sputter. No spark or no gas. Same problem. Any ideas?

check the big plug connector under the seat on left side, take it off, clean the connectors and replace, it must click back into place.
Hope this helps :silent:

Check every wire under the fuel tank. I had a similar problems and finally realise that problem is one of the brown ground wires.Maybe you have intermitent cutout. Mine was broken, engine cranked fast, tried for too or three days, checked spark plugs, injectors, everything and finally spotted that wire. Probably is something like that.

Regards

Installed new fuel injection relay, no change. Installed new spark plug wires and spark plugs, no change. Have searched high and low for loose/corroded wires, especially earth/ground. have used lots of deoxit...no change. Would bad coil/s cause these symptoms? I retired one year ago today but am feeling like I have launched a new career: "BMW K100 Detective" . I am hoping the problem is not with one of the controllers, Ignition Control or Fuel Injection Control as these are both listed at about $1300 USD!!!

the emergency stop button- lever isnt activated is it ? (right next to the start button )

it is showing neutral ? try pulling in the clutch and then start

Don't go buying either as there are used ones around at a much better price.
Usually they don't give much trouble.
When it stops check if the fuel pump runs by leaving the ignition on and turn the kill switch on and off a few times. The pump should start running each time it is turned on and keep running for 1.5 seconds. If it does not run this does not mean it is a faulty pump but gives an indication as to where to look.

Regretfully you haven't put your bike details in your signature (hint hint!), as Rick's advise is only valid for Motronic bikes (later K's). On the early Jetronic ones the fuel pump only runs when you press the starter button or when the bike is at idle and higher revs.
But the question is if your pump is running when the bike doesn't start. You should be able to hear that. Alternatively open the tank lid and see if fuel return to the tank.

Thanks Rene I spend too much time on the K11 these days and tend to forget the differences.

I've just read this from top to bottom, no one has mentioned if the plugs are wet before the bike is 1st started, if they are then perhaps the white smoke is the water in one of the cylinders or its from leaning the bike on a side stand I cant see if that has been declared yet, it seems that the symptoms mentioned seem like wet cylinders when cleared all is fine,

good point keith ..!!!!

Thanks everybody for sticking with me on this problem.

Charlie99: The emergency stop button (kill switch) is in the run position. It's a fairly new switch as it was causing the engine to die, so is not the problem. Yes, neutral shows and I've tried starting by pulling in the clutch lever.

Maybe I should recap the symptoms: SOMETIMES it will not start. It cranks and is getting fuel to the fuel rail. I've pushed the starter button with the fuel line to the injector rail disconnected; lots of fuel but no start. SOMETIMES it will start. SOMETIMES it will cut out while under way, usually for a split second, but SOMETIMES for a couple of seconds and SOMETIMES is just dies. SOMETIMES it will not start for a couple of days and then it will start. In other words, I cannot find any particular pattern to the problem.

This is not the most frustrating thing I've experienced, but it's close!

Renez: It's a 1985 K100RT

K85cster: Well, as I said, sometimes it cuts out well after warmed up. Also, it's attached to a sidecar, but I do think the white smoke is when I have parked it on and angle, similar to being on the sidestand.

Anyone have an opinion as to my question as to bad/failing coils? Are these symptoms at all consistent with that problem?

if you suspect the coils ...pull them out ...it isnt hard, take a picture of the connections so they go back together correctly , mark the high tension leads . the coils are usually marked for the correct high tension leads 1-4 , 2-3

the coils are a wasted spark system so if one cylinder is flooded more than likely the other mate will not fire anyhow ...

(which makes me think that there could be a possibility of a busted head gasket between 2 and 3 now letting water weep into the cylinders ?)

from memory the primarys should be about 2.4 ohms ....the secondarys should measure about 10,000 ohms ....

i have seen coils that have been unmeasureable on the secondarys but seemed to work , i guess in some parts of the world corrosion is an issue from constant dampness . also examine the high voltage terminals and clean them up ....you should see a brass type socket in there with absolutly no corrosion at all . if not ...make it so... you may need to make extension probes into the high volt terminal as they are burried really deep ( paper clips straightened ?)

like everything else clean up the contacts of the primary wiring which is straight from the ignition control computer under the tank,,, test the cables if you can ....also the hall effect sensors cabling is there and should be as clean as a whistle for any operation .

dont forget that without the impulse from the hall sensors there is nothing to be sent to the injector computer as well .

there are ways to test this, to be found in the forum .

1 other thing I would try Dennis is to pull the Fuel injection Terminal apart when it plays up just unclip it and replace it back in again. Reason being it could also be a sympton of a crook pin in that termination wriggling it or undoing and redoing might just cause it to identify itself to you. At present you are about to rebuild the ignition system, but before you go too deep try cajoling the FI unit to be sure it aint on the other side of the equation, thats the el verses fuel equation. I'm guessing you havent done it yet

I have had a fuel pump pack up and give similar symptoms to what you describe.
Taking care of sparks and fuel together hook a 12v source to the pump directly and run it in the tank without the engine running for 15 minutes and see if it starts running eraticly.
There was foreign matter in the pump that was causing it to lock up momentarilly and sometimes stop for a few seconds or more and very occasionally for a few minutes which caused a complete stop.
A very small particle will make them stop, I believe it is anything bigger than 8 micron is very detrimental to the life of the pump

when i first got my k the fpv was not working put a set of vice grips between valve and tank on return line and away she went i wonder if yours is starting to fail
col

I pulled the coils and measured resistances. The 2/3 coil is ok but there is no measurement for the secondary on the 1/4 coil, infinite resistance. I've ordered a new coil and will let you all know what happens after it's installed. I'm not going to do anything else until the new coil is installed lest I do something that actually fixes the problem but won't know if it's the new coil or something else.
Fingers crossed

good plan dennis ....(congrats on finding the coil issue as well ) as i recon its best to discount ...or more imortant to prove one thing, before going onto the next .
some excellent suggestions above as well .
good luck !!

New coil, same old problem. WHEN it starts and runs, it tends to cut out for a second or so every once in awhile when the RPM's get to about 4000. It seems the next time I try to start it, it will not start (starter spins, all lights ok).

Any chance this is all due to alternator brushes? The alt dash light stays on when it starts until I rev it over 2000 RPM's. Then it stays off no matter what the RPM's.

Head gasket? The inside of the oil filler cap shows no white stuff at all; pure oil. Coolant level stays full, no leaks.

Short in temp sensor wire to FI controller? Ohms between pin #10 and ground about 400.

WHEN it starts, it takes some throttle to keep it going. Before this problem, it would start on the first starter crank and would immediately idle well.

about 400ohms would be correct for 75 odd degrees c so that s nearly up to temperature ...but not if its dead cold

This week end, I had a similar incident.

Bike was running fine, I stopped the engine and it would not restart.
I let it cool down and.... Bingo the engine was running fine again.
5 min later, it would not restart.
Sunday I put the battery charger on the bike and after I could not replicate the problem.
I even warmed up the bike until the fan started to spin. With the battery fully charged, the bike restarted without a glitch (I tried at least 20 times).

This is the second time that I experience a starting or idle issue related to the battery.
Even if the starter cranked the engine.

The alternator is not delivering any power under 1,500rpm which is less than the idle.

Can you try to boost your battery and see if it solves the problem?

CF

i think you have a notable issue bert ...ive suspected the altenator (quietly ) for some interesting issues , with dimming lights and the like (possibly ignition issues as well ?)

alby and friends have replaced their regulators (in the altenator ) recently ....with some positive results ...i have been concerned about the abnormally low voltage measurements of a "well running bike" that we have noticed out here recently ......the speced voltages were way below what i would normally expect to see and i suspect dont help keep a battery well charged .

i guess age has taken its toll on some of the normally ...trustworthy voltage references ,,,more research is to be done on this i suspect ...but the simple solution seems to be exchange the regulator for a (relativly cheap ) new one ...

topping up the battery is a good idea all the same ...but i wonder if it is an indicator of something we may not have experienced before, commonly at least ....do regulators brushes etc have a used by date ?

food for thought ..

Any of that solid state stuff starts leaking sooner or later.
I have just recieved 2 new adjustable regulators from EME and will be trying them soon so keep an ear to the ground for more info.

Something to remember. The starter motor is used infrequently on our bikes and we all know (by now ;-)) that those carbon brushes are important and will wear/ need to be replaced over time. We should appreciate that the alternator also has carbon brushes (directly attached to the regulator), and that the alternator is running all the time the engine is running..........:cyclops:

I re-seated all the connectors: coils, plugs and wires, FI unit... and the darn thing has been running perfectly, no cutting out, no stalls, starts every time...for about a week. My plan now is to KEEP MY HANDS OFF. Will let you know if things go bad again. Otherwise, thanks for all your help and patience.
(an unrelated problem, non-working odometer but I'll post a new thread for that).