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1Back to top Go down   1994 K75S - Troubleshooting No Spark Empty 1994 K75S - Troubleshooting No Spark Tue Jun 04, 2024 7:27 pm

lethaljd

lethaljd
active member
active member
Hi Gents,

I'm most of the way done wiring up an M Unit in my 1994 K75S. I used Zach Ross's wiring layout (found here https://www.k100-forum.com/t11686-m-unit-wiring-bmw-k)

I'm not getting any spark at the plugs.


Please ignore the messy wiring. I want to get this running and then go back and tidy things up a bit and have made a real mess of things chasing this gremlin...

The starter engages and engine turns over
Fuel pump turns on
Injectors spray (I haven't seen it but there is fuel on the plugs when I pull them out)
There's power at the coils
The plugs are new Bosch X5DCs with new spark plug wires from Euro Moto Electrics. I tried swapping out the wires and going back to the factory wires with no luck.

I've been through Bert's troubleshooting diagram and run up and down the wiring, testing grounds, etc.

Found two interesting things:
1) Pin #3 on the female connection to the ICU - when testing for continuity with ground at the battery measures pretty high. I'm getting 1kOhm
2) When I test continuity on Pin #3 of the female ICU connector while pressing the start button I get some weird results on my multimeter. It cycles between a reading and Open Line.  Video uploaded to Youtube below. 

Is this expected? Bad Hall sensor? Do I need to go back to the troubleshooting drawing board?

    

jbt

jbt
Life time member
Life time member
Your gremlin sits in a little black box with the letters M, U, N, I & T written on.

I'll never understand why so many people are spending so much money in a useless crap that will ruin the OEM reliable electrical equipment.
Fashionistas' sheepism?


__________________________________________________
Let us enjoy the transient delight
That fills our fairest day.
    

Laitch

Laitch
Life time member
Life time member
jbt wrote:I'll never understand why so many people are spending so much money in a useless crap that will ruin the OEM reliable electrical equipment.
Because Gucci doesn't make accessories for Bricks yet, unless it owns a piece of Motogadget already. Laughing

lethaljd wrote:1)Pin #3 on the female connection to the ICU - when testing for continuity with ground at the battery measures pretty high. I'm getting 1kOhm
2)When I test continuity on Pin #3 of the female ICU connector while pressing the start button I get some weird results on my multimeter.
1) Measures pretty high? That's ≈1kΩ too high. Something is wrong there.
2) You already tested for continuity in Step 1) and Pin #3 failed the test. Testing Hall sensors while running the starter is not part of the testing protocol in the Troubleshooting the EFI guide here nor is it a protocol in BMW's LE Jetronic testing manual, reasonable as it might seem. Consider reviewing the testing procedures.


__________________________________________________
1995 K75 90,000 miles
    

lethaljd

lethaljd
active member
active member
Thank you for the helpful reply, Laitch! I’ll review again and get to the bottom of this super high reading.

For what it’s worth @jbt I bought this project bike from someone that had already stripped the bike and taken it too far to recover. An M-Unit was included in the sale. I don’t need any fancy gadgetry but it was there and seemed silly to buy all of the pieces needed to bring it back to stock. The M Unit is not the problem in this case. It is doing its job of supplying power where it needs to go.

    

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