No Sparks on my BMW K75 1989

[MAD]

After sitting in the garage for the whole winter, I tried to start my bike and it wouldn't start.
Initially, the bike acted like it was completely dead. I checked the battery and realized had gone down in voltage a little.
So, I recharged it, but still nothing.
I then realized that the clutch switch was stuck, so I removed it, cleaned it and it gave me hope.
The engine now turns, but it doesn't start still. It gave me a couple of bangs, which almost deafened me.
I checked the fuel pump, which works. The fuel also arrives to the fuel rails.
I removed the spark plugs and they appeared quite wet, so I thought I must have flooded the engine.
Upon checking the spark plugs they don't work as there is no spark.
I have then tried with a new set of spark plugs, but still no sparks.
I have been reading other topics regarding this, but at the moment I'm not really sure what to check or do to solve my issue.
Wondering if I can get some guidance from people who had similar experiences.
One more thing to mention is that when I was riding my bike during last summer, I noticed that it wasn't running properly as usual, the engine sounded differently, possibly working on only 2 cylinders.

Thanks in advance.

 

[Laitch]

How did you check the spark plugs for spark?

[The Mighty Gryphon]

Cranking a flooded engine with fuel injection will just keep flooding it.  I would try starting it with the the fuel tank disconnected.  That will blow out the extra fuel that is in the cylinders and on the spark plugs.  After a few seconds the engine should catch and you can reconnect the fuel pump. 

Make sure the battery is fully charged, it might take 10-15 seconds of cranking to get the fuel out of the cylinders.

[MAD]

Cranking a flooded engine with fuel injection will just keep flooding it.  I would try starting it with the the fuel tank disconnected.  That will blow out the extra fuel that is in the cylinders and on the spark plugs.  After a few seconds the engine should catch and you can reconnect the fuel pump. 

Make sure the battery is fully charged, it might take 10-15 seconds of cranking to get the fuel out of the cylinders.

I have tried to start it with the fuel tank disconnected, but still no luck.

How did you check the spark plugs for spark?

I removed the spark plugs (one at the time) from the engine, connected it to its respective lead, attempted to start the engine and checked for sparks while touching the engine.
 

[Laitch]

What are some of the common conditions that could cause an Brick engine to flood?

• The injectors are stuck open from particles in the fuel.   Remove all injectors to have them professionally cleaned. Clean the fuel tank if it is signficantly discolored, replace the fuel filter if its age is unknown or if it is more than a few years old. Don't replace injectors with so-called 4-hole upgrades.
• Sufficient air for a balanced fuel mixture cannot pass through a clogged air filter or snorkel. Inspect the air filter and the air snorkel for debris.
• A false signal from the coolant temperature sensor signaling the engine is warm when it is actually cold. Test the coolant temperature sensor. Instructions can be found in the Flow Chart at the link at the bottom of this page.

Brick engines depend upon clean electrical connections throughout the system wherever they are found. Many here use DeoxIT D5 to clean them, but using any dedicated electronic cleaner is better than ignoring them.
Download and read the LE Jetronic for a greater understanding of how the engine works. It is in the list at this link.

[MAD]

Thanks Laitch.

Meanwhile, I have done a few more checks:

- I have disassembled the coils and test them individually and they appear to be in good health (i.e. primary winding reading between terminals 15 and 1 is 0.8 Ohm, secondary winding reading between terminals 15 and HT terminal lead is 10 K Ohm);
- I have measured the resistance of the HT leads and I had no readings for all of the 3 HT leads, I have also checked them for continuity and I had nothing. I find hard to believe that 3 HT leads failed at the same time. Also there are no evident signs of deterioration on the HT leads.
- I have also tested the coils and the new spark plugs by connecting them to a battery and both appear to work. Initially I have used the HT leads to run this test, but they didn't work. I have then re-tried with alligator clips and cables to make the connections and it worked, which means that both spark plugs and coils are doing their job.
- I had a look at the connection to the ICU, and it seemed slightly out of place, so I have disconnected it and re-connected it, but still nothing.

At this point I'm scratching my head, as I'm running out of ideas on what to check or do to fix the issue.
Do I need to buy new HT leads?

I have also damaged one of the coil plastic connector (the one that connects to 15 and 1 on the coil) when trying to disassemble it. I have had a brief look online yesterday and haven't found any for sale.
Does anybody know if they can be purchased somewhere?

Thanks in advance.

[daveson]

Am I right in assuming that you have checked power on the low tension side of the coils and they are good? K75 leads have an air gap built in, that's why you're reading no continuity, so that's not a problem, but can you post the part numbers of the leads?

[MAD]

Am I right in assuming that you have checked power on the low tension side of the coils and they are good? K75 leads have an air gap built in, that's why you're reading no continuity, so that's not a problem, but can you post the part numbers of the leads?

I have checked the voltage for the electrical connector that attaches to the coil to terminals 15 and 1 and I have 12V. I have measured with the multimeter between terminal 15 and ground.

See below HT leads part numbers:

-1-  12.12-1 459 874
-2-  12.12-1 459 875
-3-  12.12-1 459 876

Thanks.

[Laitch]

At this point I'm scratching my head, as I'm running out of ideas on what to check or do to fix the issue.

Wear a cap while you work so you don't get a scalp infection.
Are the air intake snorkel, filter, and air box unobstructed? What was the result of the coolant temperature sensor test?

[daveson]

Set your multimeter to 200 on alternating current. With the red lead on battery positive and the black lead on coil one, pin one, what reading do you get while cranking? Then repeat for the other coils.

When the ICU is unplugged, it's a good opportunity to give the plugs a little scrub and spray with Deoxit, then let them dry before plugging it back in.

What do you mean by the ICU connection seemed slightly out of place? Slightly out of parallel, or the rubber boot was pulled back or something like that?

[jiggseob]

Carbon is a conductor.  So the plugs you took out that were soaked with fuel also had some carbon - washed by the fuel in the combustion chamber - all over the spark plug insulator and electrode.  The electricity for the spark will follow the path of least resistance, which would be along that film of fouled fuel and carbon, and not across the gap.  You would not see the electricity flowing through that film of carbon and fuel.

Dry and clean that plug.  Easiest is hold it by the very tip of the plug where the wire clips on, and heat the other end with your bic-lighter.  When it gets so hot you can't hold it, the film of fuel and carbon will be burnt off.  Set it down so you don't burn your fingers.  Wait for it to cool.  Take the tip of the knife blade in your leatherman and scrape the grey brown black crap off the insulator all the way around and as deep as you can reach.  You have to reach in and clean all the way around that white ceramic insulator that surrounds the center electrode.

A fuel-soaked film of crap on the insulator provides a path for the electricity to go to that is not across the gap.  You have to break that. If you are in the bush or a lonely roadside with no means of checking/adjusting gap, be very careful while cleaning to not bend the ground electrode or change the gap.

Use that clean, dry plug to plug back into the wire and look for spark while cranking.  Also, look for spark between the plug and the head.  If all else fails, and you are pretty much sure there is no spark, a definitive final check is to hold the plug in-hand while grounding to the engine and crank.  If you get the jolt, you have spark, keep cleaning the plugs.  If you don't get the jolt, troubleshoot deeper to find lack of jolt.

The clean new plugs you tried should have worked.  Unless you put them into a throughly fuel soaked combustion chamber, full of old fuel and carbon that won't burn, but will soak and foul even the new plugs.  But they should have sparked across the gap while outside the engine.

That is basic step-1 troubleshooting of not just your Brick, but every spark-plug fired engine thats in a no-start.

When an engine has been sitting a while, the little bit of fuel in the lines and fuel/air mixing system is degraded and won't burn.  But that crappy dead fuel will sure go into the engine and wash down a coating of carbon onto the plugs. 

I hope that turns out to be the problem here.  I do not like the jolt test for spark.  I like the thing in the picture much better.

[blackie1]

try this

[MAD]

Set your multimeter to 200 on alternating current. With the red lead on battery positive and the black lead on coil one, pin one, what reading do you get while cranking? Then repeat for the other coils. => I get 0 for all of the coils. I presume I'm doing something wrong.

When the ICU is unplugged, it's a good opportunity to give the plugs a little scrub and spray with Deoxit, then let them dry before plugging it back in. => I have tried this with no changes.

What do you mean by the ICU connection seemed slightly out of place? Slightly out of parallel, or the rubber boot was pulled back or something like that? => I think it was the rubber boot that wasn't inserted properly and it didn't look parallel. 

I have tested the water temperature sensor using a multimeter to measure the resistance between the Pin 10 of the L-Jetronic connector and ground and I got 4.4 K ohm (bike is cold and ambient temperature is 12 deg C). Can somebody please confirm if this means that the temp sensor is out of spec and needs to be changed? Thanks

[MAD]

try this

I have tried this as well without success. Thanks

[daveson]

"I get 0 for all of the coils, I presume I'm doing something wrong"

Maybe repeat the test, or better still, there is a much easier way to do the test, that is, with a test light. If you don't have an LED test light, have a look for one at your local hardware store or auto shop.

Attach the LED test light clamp to battery positive, and probe to coil pin one, the light should flash on and off while cranking.

[daveson]

Here's a video of the LED test on a K100.
The test should be repeated for each coil.

https://youtu.be/5VrtFtr07-4?si=rrvFrYYIQnggp062

[MAD]

Hi All, some updates...
I have tested the Hall Effect Sensor (HES) using the following tester:

HES tester.jpg (19.59 kB . 384x576 - viewed 435 times)
and the LED remained off, which I presume means that the HES is defective. Can anyone please confirm if I'm correct in my statement?
Can this be the cause for the absence of sparks on the spark plugs?

Thanks in advance.

[daveson]

I'm not sure how you did the test, or if you confirmed your test light works by checking it across the battery. I went the lazy way and just got a test light at the shop for $7. Was the bike battery still connected, or the Hall sensor unplugged etc. I'll guess it was unplugged because the light remained off. Testing it that way, the light remains off until you turn the crankshaft (for example with an Allen key, anticlockwise, after removing the Hall sensor cover) until the Hall sensor cup gap lines up with the sensor, then the light comes on. If checking with the plug connected it's the other way around. It's easier to check with the Hall sensor connected, I'll attach a video later.

If you checked at the coils, as with the previous video, if it pulses, that would verify the Hall sensor's as working, as well as verifying the circuit to the coils.

The coils need a pulsing earth for the spark plugs to spark, but they depend on a signal from the Hall sensor's to do it. The injectors need a pulsing earth for them to inject fuel, but they also depend on a signal from the Hall sensor's to do it. So checking the injectors is another way to verify that the Hall sensor's are working. Using a screw driver like a stethoscope against the injectors, you should be able to hear a ticking sound while cranking, which would confirm that the Hall sensor's are working. If not, the injectors could be stuck, then you could confirm if there is a pulsing earth, using a test light. I'll attach a video of this as well, later.

[daveson]

 Edit: fuel injector test. With test light clamp on battery positive, and probe to earth pin as in photo, the test light should flash on and off while cranking.

https://youtube.com/shorts/Hqttqo-y0xg?si=7zAtgZPS3FCrtO9Q

[MAD]

Some Good News!!
It turns out the issue for no sparks was the ICU!
Yesterday, I have replaced the ICU with one I bought online and it turned out to be the cause of the issue!
I now have sparks from the spark plugs! 
I haven't tried to start the bike yet, as I have the fuel tank still disconnected and I'd like to sort out a few things before I put everything together again.
I will keep you guys posted.
Meanwhile, thanks All for your support.

[MAD]

I have forgotten to ask if anyone knows where I can buy a terminal connector for the coil for my BMW K75 1989.
The one that connects to the pins 1 and 15 underneath the coil (see below photo):

coil connection.jpg (26.8 kB . 640x427 - viewed 359 times)

I have damaged one while trying to disconnect it from the coil.
Thanks.

[lewisnort]

I have forgotten to ask if anyone knows where I can buy a terminal connector for the coil for my BMW K75 1989.
The one that connects to the pins 1 and 15 underneath the coil (see below photo):

coil connection.jpg (26.8 kB . 640x427 - viewed 359 times)

I have damaged one while trying to disconnect it from the coil.
Thanks.

I also damaged this exact connector when stripping mine down, I see you're also in the UK too, I rang up motorworks and explained exactly what it was I was looking for and they cut one off a donor loom and sent it to me.

[daveson]

Ok you fixed it, goodo. I'll post the Hall test video anyway, for future readers with similar issues.

The job of the Hall sensors is to provide two outputs, one output sent through the orange wire, and one output sent through the brown wire. Normally a brown wire on a brick is earth, this is probably the only case where it is positive. Since their purpose is to count the number of crankshaft revolutions, this can be thought of as an rpm signal.

The opening in the Hall sensor cup is only a small proportion of the cups diameter, and when testing with the Hall sensor's connected, the test light will only turn off when the gap is in line with one of the sensors. Therefore the light will only turn off for a small percentage of the time that it is on.

With the test light clamp on battery positive and probe to battery negative, the test light will glow green. With clamp to negative and probe to positive, it will glow red.

This video only shows the output test through the brown wire. The test should be repeated for the orange wire as well.

https://youtu.be/P3X0zvDY6Vw?si=toSjFSML0qiJrfxt

[MAD]

All, just a quick one to confirm that it was the ICU that was faulty.
The bike works as it should now.
Once again thanks very much to those who provided support.

[Laitch]

Thanks for the update.