[SOLVED!] The no spark mystery

[Steenbeen]

I was casually driving my bike when suddenly it began 'shocking' forward. I stopped driving, put it on the centerstand, and it ran pretty roughly. I couldn't rev properly. I tried taking off again after a while, and it 'shocked' again. It stalled and wouldn't start anymore.The starter would turn, but the engine wouldn't start. It ran about 30 seconds since it first began acting weird.

This is what has been grinding my gears for the last couple of days: once back in the garage I began checking the plugs. I did get a spark at cilinder 1, but I accidentally shocked myself (I think I accidentally touched the engine block). I kept on checking, and the other plugs weren't sparking. I then went back to plug 1, and now it didn't spark. I was brave enough to touch this plug again while it started, but this time I didn't get a shock.

What I checked and how:

• The fuel pump is working; I pulled off the duct which leads to the injector rail, and when I pressed the starter button a whole lot of gas came out.
• The injectors are working: when testing the spark plugs, a gasoline smell came out of the cilinders.
• The ignition coils are probably good: I measured the resistance; they were within specs. I also swapped them out for a set I had laying around(I have a spare engine for parts), but still no spark.
• I swapped the HT leads with a few I also had laying around.
• The ECU: I checked if the big plug was still in place. I cleaned it and made sure it locked in properly.
• The hall sensor: Not sure about this one. I swapped it with the one that was attached to the donor engine. Made no difference. Checked the plug. Checked the cable going to the CDI for damage, but looked alright. I'm not sure if the one on the donor engine is working; how can I test this?
• The fuses of course. Unless there are more fuses somewhere other than the fuse box.

I feel like I've checked everything. Maybe the CDI is fried? Is it possible that I created a second problem by getting shocked? Does anyone have an idea? I tried to be as clear as possible in my methods, since I'm new to these bikes, and bikes with more complex ignition and injection in general. Maybe I made a mistake.

Thanks.

[Laitch]

Welcome, Steenbeen.
In which year was your bike made?

[Steenbeen]

It's an '86 K100. Forgot to mention.

[kennybobby]

Work thru this flowchart and it will help you determine the issue and you will solve it.
flow chart link

[Steenbeen]

I had seen that chart already. Taking a closer look, I diagnosed that it has a big chance it could be the whole ignition unit, or a damaged cabel between the ignition unit and the coils. Could it be possible that I damaged the ignition unit with that shock? I'm not much of an electrical engineer.

[Scott_]

I can add a little bit about the coil design. On these 4 cyl bikes, the spark system is a "wasted" spark design. What I mean by that is the you need to have both leads of the same coil connected for it to work properly. 1 & 4 are paired together as are 2 & 3. The coil fires both plugs at the same time.
IE, if you want to check spark on plug #1, you need to make sure that the plug wire for #4 is connected to the plug, or it won't work.

With the ign switch in the on position, if you unplug the input connector at the coil, you should be able to measure +12vdc on one the input leads at each coil. One lead is actually the power supply and the other lead is connected to the ignition computer and grounded by the computer to fire the coil when needed.

[rbm]

Check the connection at the ICU. this is the black box under the tank right by the headstock.  It controls the spark.  If it does not receive a signal from the hall sensors, then it will not cause the coils to spark.  But you've swapped the hall sensors.  So, it's possible there is a bad connection at the ICU.

[Steenbeen]

@scott: Interesting. I'll check the connection of plug #4. What cable do you mean by the input connector? There are three cables at each coil, the HT leads not included. Is that one of the two connections on what I'd guess to be the primary winding? With the third, the cable shared by the coils, being the ground? Or am I rambling right now?

@rbm: is it common that the hall sensor 'system' in it's entirity fails? As I've understood there are two sensors, 180 degrees relative to eachother. I'd guess that it's more common that one of the sensors fails, and that would result in 2 plugs not sparking, if you could confirm my thoughts?

[Scott_]

The +12v should be on the Green/Yellow wire.
The other 2 wires(one per coil) going back to the ECU would be Black/Red and Black/Blue.

If I looked at the correct diagram...... :yow

[Steenbeen]

I checked the ignition unit connector again: one of the ignition coil females seems to be missing; number 9 in this picture http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/efi-web%20page/Motronic%20connector.jpg . The only ignition coil connector is #14. Is this the right chart?
Is there anything known about this? It seems unlikely it just disappeared so I guess it has always been this way.

Edit: I checked the cables coming from the plug. #10 seems to be the black/blue cable for some reason.

[Inge K.]

I checked the ignition unit connector again: one of the ignition coil females seems to be missing; number 9

Or is it #15, wacum switch?......which was only present on earlier models than yours.

[Inge K.]

Edit: I checked the cables coming from the plug. #10 seems to be the black/blue cable for some reason.

That is #14.

[Inge K.]

The drawing is like looking from the rear side of the connector, where the wires enter.

[Steenbeen]

That explains a lot. When should there be 12V on the ignition coil input? When the ignition is on, or only when the starter button is pressed?

[Inge K.]

When should there be 12V on the ignition coil input?

When the ignition (and kill switch) is on.

[Steenbeen]

Alright. I'm getting power. Do you know how I can measure the 1,5-4V AC-current on the coils as described in the guide? I'm taking apart the module on the right of the handlebars right now. Maybe the killswitch is causing problems.

[Inge K.]

To check the coil(s) disconnect the signal wire....make a temporary wire...ground it, as soon you disconnect
it you should see a spark.
Put some spare spark plugs in the caps and ground them with jumper cables.
---------
The testing as described in the guide.....easiest would be to measure it at the coil signal wire (at the coil).

[Steenbeen]

I'll be sure to try that. Taking a break from it now until monday, been at it for the whole week. Hope to get some new insights. On the bright side, I know my bike better than ever before now :yes.

[Steenbeen]

Update: I measured the resistance between the connectors of the coils and the pins of the ICU-plug. All gave me (close to) 0 ohm, so I can guess I can conclude the wires between the plug and coils are still intact.

I also pulled out the injector rail: the injectors are injecting. But, if I pull out the Hall sensor's plug, they won't. So now I'm pretty sure the Hall sensor's intact.

I think that leaves the ICU. Any thoughts/suggestions before I order a new one?

[Steenbeen]

Update 2: it was the ICU. Plugged a new one in and it started right up. Marked as solved.

[stokester]

Update 2: it was the ICU. Plugged a new one in and it started right up. Marked as solved.

Thanks for the update.

[BlueK11LT]

Thanks again,
Does anyone know where I can find a diagram of the motoronic pins so that I can identify which one is no.19
Ive done google searches for 'K1100 motronic plug' and 'K1100 motronic pins' but iam not finding anything of much use.