1985 K100 starting issue

[ajschank]

Hello all!! I have recently acquired an 85 K100 that has been previously tinkered on by someone else and they must have gotten tired of it and I ended up with it. Anyways, its fairly clean low mile bike, they claimed 12,000 miles. It's pretty much stripped, essentials are there to make it run, but for some reason it doesn't want to. I have been working through the diagnostic flow chart, and have run to a spot where I don't know exactly how to proceed/test. I tested the Hall effect sensors and they tested fine with the LED setup. Took the fuel injectors out and they spray fuel as expected, fuel pump runs and all that.  I have 12V to the coils with the ignition on, and on the ignition module plug, but I do not have spark at the plugs. The wires to plugs all Ohm out fine, and so did the coils. It seems that the signal to ground the coils to make them fire isn't happening as I only ever see constant 12V to the Green/White wire on the coils, I would expected it to blip/ground at some point while cranking.  All grounds have been checked/cleaned, as well as the fuses. Coils look to be wired correctly per the schematic, Green/White in the middle(15) with Black/Red towards the back(1), and then the shared Brown ground wire between the two on the front part(31).  I noticed this problem originally and that's why I ended up testing the Hall effect sensors. Would it be the ignition control unit that relays the message to the coils from the Hall effects to fire?

Any advice would be appreciated!!

[The Mighty Gryphon]

Do the injectors get a pulse when the engine is cranking?  An LED can be used to watch for the pulse.  The injection control unit sends the signal from the Hall sensors to the rest of the system. 

Is the Neutral indicator working?  That inhibits starting.  What happens if you pull in the clutch when trying to start?

Another problem with starting is a dirty ignition switch.  I had trouble with it on two different bikes.  I now clean it as part of going over a "new" bike.

[ajschank]

Do the injectors get a pulse when the engine is cranking?  An LED can be used to watch for the pulse.  The injection control unit sends the signal from the Hall sensors to the rest of the system. 

Is the Neutral indicator working?  That inhibits starting.  What happens if you pull in the clutch when trying to start?

Another problem with starting is a dirty ignition switch.  I had trouble with it on two different bikes.  I now clean it as part of going over a "new" bike.

The injectors did pulse when I pulled them out and had them sitting on some cardboard to see each one eject some fuel. Would the bike still turn over if the neutral light wasn't on? I will have to try pulling in the clutch, and will also clean the ignition switch and report back.

[Laitch]

Would the bike still turn over if the neutral light wasn't on?

The engine should not crank if the neutral light is Off. That's a safety feature to prevent the moto from being started when it's in gear. It should crank if the neutral light is On or the clutch lever is pulled in. With your '85 Brick, whether it starts while it's being cranked is dependent on the fuel and ignition systems.

[ajschank]

The engine should not crank if the neutral light is Off. That's a safety feature to prevent the moto from being started when it's in gear. It should crank if the neutral light is On or the clutch lever is pulled in. With your '85 Brick, whether it starts while it's being cranked is dependent on the fuel and ignition systems.

Ah okay thanks for the clarification! It does crank over by pressing the start button in neutral(I hooked up a light to the corresponding cluster pin). I forgot to mention my Brick didn't come with a cluster for whatever reason, but i think it should still start with all corresponding items still intact, which they seem to be. Maybe I am totally wrong there with the cluster assumption.

[Laitch]

If by cluster you mean instrument cluster, the reason it didn't come with one is—by the looks of your moto—that the previous owner was attempting to make it into a café racer in part by eliminating the stock instrument and perhaps selling or discarding it, then you bought his failed project.

[ajschank]

If by cluster you mean instrument cluster, the reason it didn't come with one is—by the looks of your moto—that the previous owner was attempting to make it into a café racer in part by eliminating the stock instrument and perhaps selling or discarding it, then you bought his failed project.

Yes that is the case haha. I have yet to decide what to do with it, I don't know if I want to go cafe racer or not. Trying to make fire first!

[Laitch]

After your starting attempts, were the spark plugs wet or dry when you removed them for inspection?

[ajschank]

In your starting attempts, were the spark plugs wet or dry when you removed them for inspection?

Upon removal after some cranking all 4 plugs were wet

[Laitch]

You've got fuel—maybe too much fuel. How have you determined there is spark, and how have you determined that the plug wires are on the correct coils?

[ajschank]

To see if I had spark I pulled out plug one and held it on the valve cover bolt, making sure to leave the rest of the coils intact since I read both 1 & 4 need to be connected to see spark.
For the correct wire going were on the coils, I traced them to the coils and made sure they matched the wiring diagram from the diagnostic flow chart.

[Laitch]

You have indicated the injectors are pulsating, not injecting a continuous stream. Have you gently checked the vane within the airflow sensor for smooth operation in its full range?

[ajschank]

No I have not gotten around to testing much with the FI system asides from seeing if I saw fuel coming out of them. I can test that and check that everything is moving nicely.

[Laitch]

Checking the vane in the air flow meter is straight forward. Checking the values at the fuel injection control and ignition control pin sockets is covered in Vogel's troubleshooting guide and should be done. Injectors open for excessively long durations will flood the engine.







 

[ajschank]

All the fuel injection pins and injector pulses check out via Vogel’s guide. Check all the pins and they seem to have the voltage/ ohms/ground that’s they should.

[ajschank]

Went to do some more testing and have some questions. Was testing at the rear of the ignition module plug while cranking, and noticed that pins 9,10,14 are supposed to go to 1.5-4V when cranking and I was only seeing .2-.3V on 9 & 14 and 10 stays constant 12V. These pins are the ground to the ignition coils from the module itself. It's my understanding that 10 is the kill switch and having 12V supply there seems to make sense, and when I switch it to 'kill' on the hand controls it cuts the 12V.  I should note that battery is charged up and showing a little over 12V.

Is the voltage too low on those pins that I'm seeing? Should I suspect ignition module is the root cause here? All the other pins are good on the module aside from ones mentioned above

Thanks!

[The Mighty Gryphon]

Ideally, I would like to see at least 12.6 or 12.7 volts at the positive terminal of the battery.  There's a lot of electronics used to make the engine run, and lack of electrical power will lead to problems.  You won't be the first to have low voltage problems with the engine.

[Laitch]

Was testing at the rear of the ignition module plug while cranking, and noticed that pins 9,10,14 are supposed to go to 1.5-4V when cranking and I was only seeing .2-.3V on 9 & 14 . . .

Is the voltage too low on those pins that I'm seeing? Should I suspect ignition module is the root cause here? All the other pins are good on the module aside from ones mentioned above

Run the diagnostics again with the battery at one of the values that Gryphon indicates.

Speaking as an instruction-following drone, if an established diagnostic value table indicates the desired values but test values are as low as the amounts indicated here, then I would conclude those values are too low. I don't know what other conclusion could be drawn if the testing instrument has been correctly set. If by ohm out fine you are asserting the high tension coil terminals were testing at ~12.6KΩ then the ignition module is the more likely suspect, if it has sufficient power to distribute.

[ajschank]

Okay will retest with values Gryphon has mentioned and report back, thank you for all the suggestions so far.

[ajschank]

Okay battery was on the charger all night and battery voltage was at 12.89V when test started and concluded at about 12.72V, I retested every pin on ignition module.
Pins were all good except for a couple I found some outliers compared to the guide, said in my best monotone testing drone voice.

Pin   6   was constant  5V        which is starter switch signal expecting 12V when starting was running, seeing 5V always, regardless of starter running or not
Pin   9   was reading   0.394V
Pin   10 was constant 12.89V
Pin   14 was reading   0.409V

So even with a fully charged up battery those pin values of 9-14 don't seem to change.. Now possibly that could be related to the low voltage from starter switch? Again thanks for the help!!

[rbm]

looking at the schematic for the early K100, pin 9 and 14 are switched ground signals.  I'd expect to see 0.2 - 1 V relative to ground with the starter turning, depending on how responsive to changing signals your voltmeter is.  A slower responding voltmeter will read a lower voltage because it can't accurately follow the changing signal.  As for 12V on pin 10, that makes sense.  The voltage listed in Bert's troubleshooting guide seems wrong. If you look, pin 10 is listed twice in that chart so it is a mistake in the chart.  If you're getting 5V on pin 6 all the time, irrespective of the start switch pressed or not, that's a concern.  Need to find out why?  Pin 6 is connected to a power source.  You should see 12V or so when the start button is pressed, otherwise nothing.  Can you remove the plug from the ICU and test the voltage on pin 6 again?

[daveson]

Yep 9, 10, 14 looks like a typo,  should be 9, 12, 14 to the coils.  12 only applies to the k75 which has three coils.

The front coil should have black/blue to 1, the rear black/red (power is green/yellow, not green white, just checking)

[ajschank]

Looks like pin 6 is reading how it should, either an error on my end or my meter wasn’t quite making enough ground contact. Also I’m issuing a fluke multimeter, it seems fairly responsive. Double checked black/blue on first coil in the rear pin, and green/yellow is connected in the middle of both, and black/red on rear most coil on the rear pin.

My voltages seem to fall in the range you mentioned rbm, so maybe I ignition module can be ruled okay?

[Laitch]

My voltages seem to fall in the range you mentioned rbm, so maybe I ignition module can be ruled okay?

I think a coin toss would work right about now.  Anyway, mosey on over to this post and take a look a BMW's ICU/FICU guide by clicking on the link at the bottom of volador's post. This is one of the many manuals supplied to Motobrick.com complements of volador.

[rbm]

My voltages seem to fall in the range you mentioned rbm, so maybe I ignition module can be ruled okay?

Yes, It's a good chance that the ICU is OK.  It's that 5V on Pin 6 all the time that concerns me.  There's something going on there that has to be revealed.  That's why I asked to measure the voltage without the ICU in circuit, to determine if there is another problem in play here. The 5V level indicates that there is a load drawing the voltage down and it has to be revealed.

Geez, diagnosing a problem halfway around the world on a K-bike is like a doctor in USA diagnosing a disease in a patient in Australia by reading a report by a diagnostician in France. Crazy.