Hello, I have a problem w my '88 K100. Garaged it in December with no problems, bike was running ok . Now, the weather turned sunny and warm and I went & tried to start the bike. Battery is ok ( and recharged ) , fresh fuel and the bike starts, runs rough, won't idle, and dies. Then I cannot restart it because is flooded. If I disconnect the fuel pump and sender connector, it starts w the remaining pressurized fuel in the fuel rail then I have to reconnect the plug in order to maintain the bike running. Still won't idle , runs rough for a couple minutes after that is ok but still dies at idle with the choke on. And if dies, is flooded again , so no start only if I repeat the plug off / on procedure. I took the bike for a short run and it pulls strong , no hesitation. Clearly dies again if I let it idle. From time to time runs only in 2 cyl. always the same 1 and 3 so on different coils . Swapped the injectors and plug leads with no effect.

Things I checked:
- Vacuum leaks - found none
- vacuum hose at the FPR is ok
- cleaned all the plugs ( ecu, ign. module, ground etc )
- injectors spray pattern is ok ( pulled out the fuel rail still connected to the supply, return hoses and injectors plugs, and then cranked the the engine )
- measured the coils resistances, all seems ok
- measured the MAF output
- measured the fuel pressure - in spec.
- performed a leak down test and the results are between 20% and 26%
- verified hall sensors with led lamp, works ok
- I have bright strong spark at all 4 plugs
- injectors are energized

Things I replaced:
- new water temp sensor
- new set of plugs
- replaced the ECU with a spare
- replaced the ignition module
- air filter - new

The bike has 39 000 km.
And now I am out of ideas....what I am missing?? Any thought greatly appreciated . Thanks

Check the fuel pressure regulator is regulating to 36psi. Connect a pressure gauge to the fuel rail where the hose to the FPR joins the rail and dont forget to make sure the Vacuum hose is connected at #4 throttle body as it easily gets disconnected there when connecting a pressure gauge.

Rick G wrote:Check the fuel pressure regulator is regulating to 36psi. Connect a pressure gauge to the fuel rail where the hose to the FPR joins the rail and dont forget to make sure the Vacuum hose is connected at #4 throttle body as it easily gets disconnected there when connecting a pressure gauge.

Thank you , FPR is ok , it was the first thing I checked.

i think we have seen on a couple of occasions ...the maf (air flow meter) having a stuck vane .....ie: the vane was sticky ..... having read that the return springing suffers over time .....i wonder if this is a cause .... and doesnt return properly ...intermittently

just a thought to throw in the mix

yes i saw that you checked it before ..... may be stick your finger in there with the air filter off and see if the moovement s smooth ...wishing you luck mate ...you certainly have a brain teaser going on there

I will check that. The vane seemed to 'glide' smooth , but it does not hurt to check again.

after a new session of connectors cleaning, now it runs relatively smooth but rich . Cold start is ok , warm and hot start is not - the engine is flooding and it can be started only with disconnected fuel pump. Ideas?

Have you checked the temp. sensor resistance at pin 10 on the L-jetronic connector when the engine is hot?, should be around 250 ohms.

Could be bad connection at connector between frame and engine harness, or other connections in that circuit.

[quote="aquachrono23
- injectors spray pattern is ok ( pulled out the fuel rail still connected to the supply, return hoses and injectors plugs, and then cranked the the engine )
- measured the MAF output
[/quote]

Hi there, I think of two things:
1- Check the injectors with a testing machine, this way you can test the injector closed, if the injector do not closes, drips while testing, then you can not control idling and will have fuel floodings. Usually cleaning the injector solves this problem. The machine also allows yo to check the fuel flow, and the spray patterns.

2- Check de MAF´s idle adjusting screw. If to closed youll have a rich mixture and will be unable of sustain runing at idle and will also have rough running at higher rpms. For the setup you con check here: http://skylands.ibmwr.org/tom/tech/co-setting.html

Hope this helps
Best regards

JAP

Thanks Jap , I will try to adjust the MAF tomorrow. If this does not solve the problem , I will send the injectors for another cleaning .
Best regards,

aquachrono

This description fits my bike too. I replaced the fuel hoses, had the injectors refurbished and generally changed out the rubber bits that would be deteriorated on a 28 year-old bike. Now it fires immediately when I hit the start button, but dies just as fast. After many, many tries I can coax it to run but it still will not idle well. It ran extremely well before I undertook this maintenance I would really appreciate it if someone explain in greater detail the bit about the air flow sensor. Perhaps post a photo of this door that may hang up and the spring that apparently can grow weak? I am inexperienced when it comes to working on FI. At this point I feel like I am grasping at straws....

brickrider wrote:This description fits my bike too. I replaced the fuel hoses, had the injectors refurbished and generally changed out the rubber bits that would be deteriorated on a 28 year-old bike. Now it fires immediately when I hit the start button, but dies just as fast. After many, many tries I can coax it to run but it still will not idle well. It ran extremely well before I undertook this maintenance I would really appreciate it if someone explain in greater detail the bit about the air flow sensor. Perhaps post a photo of this door that may hang up and the spring that apparently can grow weak? I am inexperienced when it comes to working on FI. At this point I feel like I am grasping at straws....

If it was running well before the maintenance work then I would doubt very much that the MAF needs any attention. Don't try to adjust the MAF unless you are quite sure that the problem is there. Have you replaced the fuel filter and check fuel pressure it could also be a small piece of rubber that was dislodged during the work lodged in an injector filter or the fuel pressure regulator. I have seen this sort of thing before.

I did further research on the mass air sensor (?) and I am satisfied that it is functioning as it should. I found a kink in one of the fuel hoses I installed (I mis-routed it and caused the kink) -- all smiles then, certain I had found the source of the problem. No joy.
I've thrown in the towel and taken the motorcycle to the local shop where I hope they can sort out the problem.
I have replaced the fuel filter, the rubber boots between the TB and the head, all the fuel and vacuum hoses and checked the air filter (which seemed to be good for many more miles) as well as had the fuel injectors tested and reconditioned.
When they were returned, this bit of advice accompanied them: " For best performance from your freshly serviced fuel injectors clean the throttle valve and idle controller. Clear the ECM adaptive memory and perform a relearn using the factory approved procedure."
I did clean the TBs and checked the idle controller (which in this case seems to consist of the threaded screw on the TBs), but I don't quite understand the recommendation about the ECM. Would this be pertinent to a 1985 K100RS? It seems to assume a higher level of electronic sophistication than exists on this old bike.

yes i think i agree ....im reading all those things apply to much later versions of fuel management - ecu configurations .

ours is a pretty simple system

maped air flow ....temperature and preprogramed advance curves

i guess we just have to make sure all those things are in tolerances

we have seen a few issues of running rich lately

might be good to read rob lentinis article on maf adjustment ......

http://skylands.ibmwr.org/tom/tech/l-jet-cal.html

the most important things are the co readings .....given that all the other measurements prove to be acurate .......

inge posted a good measurement guide for maf vane measurements as well ...although im still a little mystified as to the tension (return spring ) required to acheive those readings in real "running mode" and of corse that the vane actually returns to zero when at idle i guess .
that answer might just be the co readings at revs specified .
and i would make sure that the measurements specified are tested first .

http://www.flyingbrick.de/pdf/Luftmengenmesser.pdf

i hope to be able to one day get mine right ....20 killometers to the litre is probably pretty common but i recon that about 25 killometers to the litre would probably be closer to the "left factory " design fuel consumption,, we all have different riding tecniques and landscape that would affect this .

I have measured the ignition leads and I've got 10.2 KΩ , 10.2 KΩ, 12.45KΩ, 7.56 KΩ . Also , I have measured the spark plugs NGK D(R)7EA - two of them are 3.75 KΩ , other two are near 1KΩ. I also have a new set of Denso plugs those are all 6.45 KΩ. It runs better on NGK's , it pulls strong and runs round but I still have the hot start flooding issue . Anyhow, it is time for a new set of ignition leads? From what I read the leads has to be around 6 KΩ and mine are way off. I will buy another set of plugs too .... Can someone please measure the ignition leads?

I measured again the coils. 2.6 Ω at the primary and 10.1 KΩ at high voltage terminals on both , not 12.6 as stated in EFI troubelshooting PDF. But there is bright strong spark at all the plugs. Do I need a new pair of coils?

mine were about 10 k also

I would say that is within tollerance for the coils but you say you have resistive leads and plugs. If you usr OEM leads use D7EA plugs and if you use resistive plugs like DR7EA then you should use non resistive leads like the blue silicon ones available from most auto stores.
I am not a big fan of the OEM leads as I have seen a moisture build up inside the metal shield on cold mornings and cause very hard starting, not just on BMWs but many Japaneese bikes as well.

2 years ago I had a similar problem.
The bike was running perfectly, I stopped for a 5 minutes shopping and when I took it back, it wouldn't idle. (I had to maintain a min of 2000 rpm to avoid dying).
Over the next 2 days I really scratched my head on this one. (replacing spark plugs, MAF, EFI..... with no joy)
Battery seemed OK and starter was running strong. I was still chasing the gremlins when suddenly, the starter refused to run because of low voltage.
I turned off the ignition, waited 5 minutes and then the battery was OK again but the bike was not idling.

This gave me a hint and I swapped the battery. The bike ran perfectly after that with a smooth idling.

Even if the old battery was delivering 12.5 volts (when the engine was not running), it seems that when it was under load at idle, something was wrong (even if the headlight and flashers were working)

Remember, the alternator doesn't charge under 1,500rpm and you solely rely on the battery to run the engine and accessories (headlights,horn, flashers).

Is it worth trying another battery? Yes.

CF

great observation bert .....

put that in the knowledge base .....hope i can remember it next week ...giggle

I measured the fuel pump pressure (the fuel rail pressure is in spec. ) and it is 95 PSI. The literature specify a pressure of 65 PSI , more than that pointing to a problem with the internal relief valve. Since the FPR is maintaining the rail pressure at 35 PSI I don't think that a bad relief valve is responsible to my warm/hot start flooding. Also, I have noticed that the MAF air temp sensor ( pin E - the one in the middle of the MAF electrical connector ) has no corespondant in the wiring of the bike. The original wiring has only 4 wires at that connector , not 5 . Now ...why do I have a temp sensor if it is not used?
Ths flooding issue is making me wanna scrap the bike.

As we talk in a previous post, the water temperature sensor affects the richness of the mixture when the bike is cold. Have you tested the sensor?

Have you tried to disconnect the idle switch on the back of the throttle body?
Maybe the switch is bad and signals to the engine that you are on full throttle.

What kind of K100 do you have? An RS with Motronic or an older one with Jetronic?
This is why it's important to put insert the year and type of bike you are riding into your signature.

I am assuming that you own an older model, but if it's not the case, the troubleshooting procedure is different.

CF

88 model bert ...was in the first post ...was that when they brought out the first 16 valve ?

Yes, 1988 K100 RS

Water temp sensor is new. And tested it again today.
With or without idle switch connected , it makes no difference. Anyhow , it is tested and adjusted.
Hot or cold, after is started , the bike runs ok, it idles but still running rich, the plugs are black . But the warm and hot start is impossible without disconnecting the fuel pump connector , then it starts w the remaining pressure from the rail and I have to quickly reconnect the connector so the fuel still enter the rail.
Believe me , after all the things I checked and replaced I really have no clue what the problem is , otherwise I do not post questions .

what was the measurement at pin 10 of the efi computer aqua cold ...then warm ?

charlie99 wrote:88 model bert ...was in the first post ...was that when they brought out the first 16 valve ?

88 model should be a 4v with Jetronic. the 16v rs is listed from 1989 on the ETK.
If this is like the car in NA, In March some manufacturers are already selling next year model.....

He did mention that the AFM was checked, a 16V ain`t got that.

This is a long shot but thats what we are looking for now as it seems most of the normal problem places have been checked.
There is a rich start system on these bikes. when you hit the starter button that sends a signal to the ECU to make a rich mixture to make starting easy. The wire is on pin 4 of the ECU plug and is black with a yellow trace, if this wire has a feed of battery (+) then the ecu will run rich as it thinks you are still trying to start. This wire cannot be disconnected easily and would need to be unsoldered from the pin 4 on the plug or snipped and then re joined but when I read this thread from the start it was something that seemed possible.
Measure the voltage at the pin with the key on but dont press the starter button, there may be enough voltage (approx 5v) to make the ECU react but not to make the starter relay switch on. Like I said it's a long shot but worth it and easy to check.

Rick, I verified the number 4 pin at ECU plug . Indeed there is a 5 volt feed when start button is pressed. The black/green wire connected to pin 4 can be traced at the plug under the tank , left hand side , 5 pin plug , 4 used ) . For test reasons I have cut the wire near that plug and inserted a push button so I can energize that number 4 ECU pin only when I want, and the rich start function is by default disabled. If I press that push button at the time when I hit the start button the system works with the rich start function enabled. I tryed cold start w/o the rich start enabled and it works ok . Unfortunately the weather is not ok for riding for almost a week now, so a hot start test I did not performed. Anyhow, the engine was and is still running rich ( was running rich all the time the problems appeared ) . The plugs are all black . I am not confident bypassing the rich start function this will solve my hot start problem .

aquachrono23 wrote:Also, I have noticed that the MAF air temp sensor ( pin E - the one in the middle of the MAF electrical connector ) has no corespondant in the wiring of the bike. The original wiring has only 4 wires at that connector , not 5 . Now ...why do I have a temp sensor if it is not used?

Only four wires is needed: positive, ground, air flow signal and air temp. signal.
Air temp. sensor measure resistance to ground.
If I don`t remember wrong you would measure ground also at the centre pin.

Sorry, but have no contribution to your flooding problem.
But both Charlie and I have mentioned pin 10 at ECU connector....since its been no feedback at this specifik measurement (exept WTS is new and tested) I presume the measurement is found to be within spec?