Hey all,

So I purchased a non-running 85 K100 and I'm having some trouble getting it started, I figured I'd seek guidance here. The bike is currently hot-wired since the ignition switch was busted and I'm waiting on the new one. New starter relay and new battery, PO says he installed new hall sensors and EFI box (one above the battery). Here's where I'm at so far:

• Fuel is flowing, I can feel the pump running and the connector under the tank is receiving 12v.
  
• FI relay is good
  
• Grounded spark plug 2 & 4 and was getting no spark
  
• Both coils are reading 3.5 ohms of resistance
  

I noticed that there was a bundle of wires under the tank that connects to the ECU I think, and when I grabbed it I could here the FI relay clicking and a few other click noises coming from the bike. Cut open the bundle to find this horrible mess! I have no idea what the PO was thinking or trying to accomplish. Any suggestions?



Here's one of the spark plugs.



Also, there are these random cut wires in the relay box, any idea what they're from?

I would say he has cut off the connector for special equipment to use the plug as a replacement for the fuel tank connector. If you insulate those wires all will be good there. In 1st pic looks like he has taken the rubber boot from the ICU and the ICU appears not to be there. It's an aluminium box below the top frame tube right at the front and that long black multi pin connector is what connects to it. That could account for no spark if the Ignition Control Unit is MIA.
A good harness would pay well.

Yes, looks like the ICU is missing as well as the rubber boot that goes around its connector.

As stated, the cut wires are most likely from the alarm/special equipment connector.  The usual reason for that connector to be cut off on an 85 is to fix the fuel tank connector when it goes bad since it is the same type of connector.

Did one of these come with the bike? (ICU)

ICU is present and accounted for, that's just a bad angle so you can't see it. The PO had cut a spliced in a trailer connector to the fuel tank. I'll have to take some time and splice in some new wiring into the harness and see what happens.

No spark on 2 and 4 is strange since they are on different coils. 1/4 and 2/3 is the coil arrangement.

Is it possible plug leads for 2 and 4 are reversed..........

I think you'd still get a spark even if the leads were reversed. My guess is that either both the leads or the lead's connections are faulty or those plugs are KaKtus.

Sometimes the connection inside the coil towers can get corroded and also badly inside the plug cap.

What plugs are in there and are the bobbins on the plugs present and accounted for?

The missing sparks suggest coils do work as the coils fire both plugs at the same time, wasted spark.

You could swap the two plug leads on the coils so they are still on the same coil. Swap the 2 on the front coil with each other and do the same with the 2 on the rear coil. If the problem moves then it's leads or plug caps or the connection inside the coil tower. If the problems stays as is then it's plugs or far more unlikely the same problem inside both coils.

Always possible a PO changed 2 of the leads and created a problem in doing that by fitting wrong or bad leads.

Took a little more time today to try and diagnose this. Cleaned up the wiring under the tank, no more ghost clicking and it looks much better. Also took the time to clean the large ground as well. Still no spark. Checked resistance on the ignition wires and they're still good. Pulled and replaced all 4 spark plugs with new NGK D7EAs, making sure to keep the little terminal for the ends. Double-checked ignition wire placement was all good. Also checked and saw that the ignition coils are receiving 12v. After all that, when grounding a spark plug I'm still not getting any spark. Any suggestions?

If coils are getting signal the fact that you have spark on one plug lead from both coils suggests the issue is within the coil itself or the plug lead/cap.
 
Swap the plug leads at the coil ends and then see if the spark moves with the swap.

If the spark moves, the coils are good and the lead is kaput.

If the spark doesn't move the coil is suspect and the leads are good.

Strange to have same thing on both coils. Early coils are known to fail but both failing same way at the same time is not normal.

Tricky thing with those plug leads, correct readings don't always mean there is a good electrical connection on the plug cap end.

Also might be worth pop up a photo of the coils you have.

I'm not currently getting any spark from either coil. I currently have the old style coils I guess? They're both solid black.

Try reseating the L-Jetronic connector. (The L-Jet is the silver FI computer that sits under the rider.)

I think it is extremely unlikely that both coils failed completely at the same time.

Too bad I don't live in Seattle anymore or I'd come take a look at it for you.

Could be the earth connection on the coils?? Check you have continuity from there to the earth point on the gearbox.
Try cleaning and re-seating the ICU plug up behind the headstock. This has been known to cause problems from corroded connection or simply a loose plug.
Did you check for corroded connections inside the coil towers?

I swapped my coils with those on the LT a few weeks ago. Made quite a difference and I put it down to the cleaning of the connections underneath the coils. There is are two plug connectors plus an earth. The coils are marked with a label as to the colour of the connectors, I cleaned them all up and cleaned out the plug lead sockets, used an earbud [useful things them] with some 800 grade wrapped around it.

If your spark is now vanishing at the coils still seems like the earlier test that gave a spark from only one plug lead on each coil showed they were working but maybe can't build up the current for the second spark in time...........no fear you were given 2 K75 coils.....?

I'll have to take a look at the connections and give them a good cleaning. I've never actually gotten any spark from the coils too.

Bronze Lion wrote:I'll have to take a look at the connections and give them a food cleaning. I've never actually gotten any spark from the coils too.

But the plugs gave a spark? Were the leads connected to those coils?

No I've never gotten any sort of spark from the plugs, even after replacing all 4 of them.

From your first post I think we were assuming it was only 2 & 4 that weren't firing.... but you actually don't have any spark at all.
I'd say that because both HT circuits are out, its gotta be something further upstream. As Duck said, its unlikely both coils would fail at the same time.

Firstly, make sure you're getting earth continuity on the brown wire at the coils.

Also, with ignition on, you should be getting 12v on the yellow/green wire at the coils. This power comes directly from the ignition switch (green wire) via the kill switch. You've said that you've had to 'hot wire' the ignition because the ignition switch is missing. Could be a problem here.

Then take the tank off and check your ICU connector. One of our members here struggled for weeks only to find this plug was loose.

Good luck

I had no spark issues and as said the connector to the ICU under the tank [when it happened on the LT] and also the FICU under the seat [when it happened on the RT] were the issue.

Interestingly the ICU gave me no starter either, the FICU allowed engine to turn over.

Also, temperature sensor needs to be there and not recording overheat, it also will inhibit starting if it considers there is an overheat.

Holister wrote:
Firstly, make sure you're getting earth continuity on the brown wire at the coils.

Also, with ignition on, you should be getting 12v on the yellow/green wire at the coils. This power comes directly from the ignition switch (green wire) via the kill switch. You've said that you've had to 'hot wire' the ignition because the ignition switch is missing. Could be a problem here.

Then take the tank off and check your ICU connector. One of our members here struggled for weeks only to find this plug was loose.

Good luck

I've got 12v, I'll check the ground tonight. I pulled the ICU connector yesterday and gave it a good spray with electrical cleaner and made sure it was fitting nice and snug.

92KK 84WW Olaf wrote:I had no spark issues and as said the connector to the ICU under the tank [when it happened on the LT] and also the FICU under the seat [when it happened on the RT] were the issue.

Interestingly the ICU gave me no starter either, the FICU allowed engine to turn over.

Also, temperature sensor needs to be there and not recording overheat, it also will inhibit starting if it considers there is an overheat.

Is there a way to test the ICU and FICU to see if they're good? I'll take a look at the temp sensor this evening as well.

This is just a long-shot, but it's possible that the cable from the HES timing plate is disconnected. Under the tank at the front on the R/H side you'll find the connector #3 in the diagram below. You could also check behind the T-shaped timing cover to make sure everything is in place there like sensors/timing plate/rotor. If unsure, post a photo.

I think failing this, the ICU may be faulty or you have a problem with the Hall Effect Sensors but I doubt both sensors would fail at the same time.

Ok, to do list for tonight:

• Inspect behind timing cover
  
• Clean coil grounds
  
• Check temp sensor
  
• Double check FICU & ICU connectors are clean and seated
  

Quick question, my understanding is that the coils receive 12v all the time, and fire when they recieve a grounded timing pulse from the FICU..or is it the ICU? Is there a way to verify this?

Is there a way to check to see if the FICU or ICU are dead or dying? I'd like to avoid shotgunning parts at this if necessary. 

Thanks all for your help, I appreciate it. I will say, working on this bike makes me miss my old 650GS... I was so spoiled by the underseat gas tank!

Holister I was just about to type about the connector from the timing plate when I looked up and saw your post.......

And yes both Hall sensors failing at the same time is unlikely. However disconnected or broken wiring [where it passes the radiator in particular] would likely cause both of them to go down.

..... disconnected or broken wiring [where it passes the radiator in particular] would likely cause both of them to go down.

Good point Olaf.

Bronze Lion wrote:.... coils ..... fire when they recieve a grounded timing pulse from the FICU..or is it the ICU? Is there a way to verify this?

The Ignition Control Unit, as its name suggests, controls the spark ignition. Each coil gets its own signal.
The FICU receives a pulse from the ICU which it then 'shapes' and sends to the injectors. It has nothing to do with spark ignition.

You can test the temp sensor on FICU plug pins #10 & #13 (count from the lead end). You should be reading 2.5kΩ @20ºc. The temp sensor only inputs to the FICU.

While you have the tank off, clean the main earthing point on the centre frame spar.

Thanks for input. I'll check the resistance of the Halls Effect wiring, see if there's a break anywhere. I just gave the ground a good scrubbin last night.

Is there a way to actually test the FICU to see if it's dead/dying?

A really good resource is the 'Trouble shooting' link off the Portal tab. This is a must read! About two thirds the way down you'll find a table outlining expected meter readings at the ICU Plug. (DO NOT METER THE ICU ITSELF). This will tell you useful info about inputs to the ICU and other connections but it won't give any indication about the condition of the ICU itself. AFAIK the only way to test the ICU is to swap it out.
Here also is the procedure for testing the HES. BE CAREFUL. THEY CAN BE FRIED EASILY!!!!  as the wiring connections can be a little confusing. Heed ALL the warnings on the troubleshooting page in YELLOW.

Just below that is a similar table for testing the FICU. But similarly it won't tell the condition of the unit itself. You'll need to swap it out to test.
IMO.... for the time being, your plugs are wet, I would have to assume the FICU is working. Focus on the spark ignition.

Just below these tables is info about testing your coils.

Swap it into another K100 that you know runs.

Looks like I have some reading to do, thanks!

Hi

Please check your battery. Just my opinion. 

Cheers

Fresh battery was one of the first things I did. Battery tests good and spins the starter nice and strong.

Ok, managed to get a free moment this weekend to work on the bike. Took measurements at the ICU and everything checked good. Ground at the coils tested good. Took a look under the timing plate and everything looked okay. One thing I was having trouble with was the temp sensor. Tried to measure it via Pin 10 and ground and didn't get anything. Took the connector off of the temp sensor and measured to see if there was any breaks in the harness, and it tested good. Reconnected the temp sensor, measured from Pin 10 to ground and got...nothing at all. Any ideas? I'm at a loss here.

Bronze Lion wrote:Ok, managed to get a free moment this weekend to work on the bike. Took measurements at the ICU and everything checked good. Ground at the coils tested good. Took a look under the timing plate and everything looked okay. One thing I was having trouble with was the temp sensor. Tried to measure it via Pin 10 and ground and didn't get anything. Took the connector off of the temp sensor and measured to see if there was any breaks in the harness, and it tested good. Reconnected the temp sensor, measured from Pin 10 to ground and got...nothing at all. Any ideas? I'm at a loss here.

Sorry to hear of your electrical woes. Electrical issues are my least favorite diagnostic.  
Assuming you have a known good sensor. 
It is my understanding that when temp is critically high the sensor shorts to ground to both illuminate the idiot light & then shut down engine to prevent damage. 
I am new to Kbikes, but not to troubleshooting/diagnostics in a variety of different fields.
When you say nothing at all, do you mean 0 ohms or infinity?
Zero ohms would shut off the bike. Infinity would be as though it was out of circuit.
There is probably more to it than that. But this is my simple understanding of how this system works.

I may be completely wrong and apologize should that be the case.

Just wanted to show some support for your efforts.

Troy

Thanks Troy. When reading from Pin 10 I was reading Infinite. Per Hollister's suggestion, I was expecting a reading of around 2.5K.

You can test the temp sensor on FICU plug pins #10 & #13 (count from the lead end). You should be reading 2.5kΩ @20ºc. The temp sensor only inputs to the FICU.

So if the temp sensor is working correctly it would read as open?

Bronze Lion wrote:So if the temp sensor is working correctly it would read as open?

No. Holister's information is accurate for a cold engine. The temperature sensor is explained in the K100 troubleshooting guide found in the Portal.

Scrolling through that guide you'll find two methods of determining water temperature sensor values. One way is directly with the sensor; the other method is the one you're using. If you are using the correct pin, you have a problem—maybe with the sensor, maybe with the control unit, maybe with your test instrument.

tagaz wrote:
It is my understanding that when temp is critically high the sensor shorts to ground to both illuminate the idiot light & then shut down engine to prevent damage. 

Troy

The K100 and K75 2v engines have 2 sensors within the one housing. One is used to control the fan which turns on at 103°C and the other gives feedback to the ECU and turns the idiot light on at 109°C. If the engine temp reaches 111°C the ECU will prevent the engine from starting but will NOT shut the engine down because you don't want to be stranded on the inside lane of six lanes with a dead engine.

RickG thx for sharing the details of the temp sensor operation.

How does one go about bypassing the temp sensor to possibly get bike started.
I believe if it is bypassed & bike starts.
Then it is necessary to trouble shoot temp sensor system/circuit to locate the exact cause of this concern.

Is this a logical diagnostic method?
Or how would you trouble shoot this no start problem?

If the temp sensor is out of the circuit or open circuit then the bike will not start.
I doubt the sensor would ever get down to zero ohms. It's resistance at 100°C is 200ohms ± 10% at a guess I would sat that 150-120 ohms would see the no start situation