k75C No Spark No Injection!

[Lazarus]

First off, I would like to introduce myself to the forum. I am a BMW fanatic at heart and have worked on several M cars Ive owned over the last decade. This 1986 K75C with 27,000 mls is my second motorcycle and I am very excited for some long distance two wheeled cruising in my future. With that said, down to the nitty gritty...

Starting the bike up after lots of refinishing and maintenance work and having some issues. Starter sounds healthy and turns motor over easily

-Brand new battery reads 13 volts
-No Spark on any plugs
-Fuel pressure at rail, freshly cleaned injectors, but no injection into cylinder.
-All grounds have been meticulously cleaned, battery ground and under tank frame grounds
-On EFI, Multimeter positive at pin #12 and negative at ground I am getting no pulsing negative voltage. Am I doing this correctly?

Trying to rule out everything else before swapping the EFI. Could this possibly be the HES?

Thanks in advance for the help!


UPDATE / FIXED
I replaced the Hall Effect Sensor and she started up beautifully

[K75rt]

http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/bike-wont-start1.htm

Seems like you're almost there in diagnosis.

[Lazarus]

I have been using that page to troubleshoot. Been very helpful. When doing the test readings on the pins of the FI computer connection, I get some strange results

PIN #1............  ~135mV
PIN #2............ 0V
PIN #3............ 0V
PIN #4............ 9.2V

These values are quite different from what is expected. I am especially concerned about the 9.2V on PIN#4. Can anyone shed some light on this?

[Scott_]

I would say that the reading on pin 4 is not out of line if the starter motor was turning the engine over when you took that reading.
Not uncommon for battery voltage to drop 3 volts or so when starting.

I'd be more curious why you have no voltages on pins 2 and 3 from the throttle position switch, unless you had it disconnected.

[Lazarus]

Been using this to test the female ICU connector pins. Am I missing something? How am I supposed to get any readings from the hall sensor pins (power and ground) when its not plugged into anything?

[Scott_]

I guess I should ask which connector you are taking your readings from. The 13 pin jetronic connector or the 15 pin ignition connector. The values you posted make sense to come from the 13 pin connector, if you measured those on the 15 pin, you got something really wrong....

[Lazarus]

Values I posted came from the 13 pin connector. My latest post was concerning the 15 pin ignition connector

[Scott_]

Gotcha, ok.
Not sure how in depth your maintenance was could you have disconnected the hall sensor plug, and forgot to put it back together? I've forgotten many a connector when working with wiring.......

To test the hall sensors, you will need to supply a + and - 12V to pins 2 and 3 respectively to get power to the sensors.
Like is shown in Bert's diagrams there, you will need a 12v LED, not a regular filiment light bulb.
Connect the + side of the LED to the + 12v source(pin 2) and then connect the - of the LED to pin 5. When the motor is turning the LED should flash.
Repeat the same for pin 13 instead of 5. LED should flash while the engine rotates.

If this test fails for either or both, double check the 5pin connector buried in the wiring nest under the fuel tank, make sure none of the pins pushed out of the connector body.
If the connection is good and clean, and the test still fails, you could check for a bad/broken wire termination at the hall sensors located behind the T shaped cover at the front of the engie. Other than bad connections, the hall sensors could be bad if the LED's still don't flash. The wire bundle is fairly robust, insulated wires bundled together with mesh shielding over the bundle, and more insulation over the shielding.
Not that I haven't heard of wiring going bad, I'd find it very unlikely, except if in the case of an engine fire or something like that, that would melt the isulation and short everything togher.......

The terminals I listed above are in the 15pin terminal strip that you have disconnected there.
You can do the same test from the 5pin plug of the hall sensor harness if needed. Just follow the diagram in Bert's document.

[Lazarus]

Thanks for the in depth response.
 
I have already tested both sensors using Berts process with a 12volt LED and they both work. Connector is very solid and I have continuity across it.

I will add here again, I do not have continuity between battery ground and HES shield/ground on female plug

[rbm]

That may be normal because the shield is only grounded at one end, not both.  It stops ground loops from forming.  Have you tested the other end?

[Inge K.]

The shield is grounded in the ignition ECU.

[Lazarus]

I agree on the shield not too concerned about that. Im leaning towards the ICU. At one point the ignition was switched on before the ICU ground was secured  :dunno2: perhaps that zapped it.

There is no continuity between battery ground and brown HES ground

[Lazarus]

The wires from the Hall sensor to the CDI plug as well as CDI to Ignition coils are good with no shorts. I have also tried a different Ignition computer with no Dice. My Hall sensor is getting 11.4V with the ignition on. Is this enough? Any other ideas?

[Scott_]

Just to clarify where you are at with this.

Injectors do not pulse: tested with LED at injector connection? You did say no pulsing on term #12 with a multi-meter though.
No spark at plugs.
You have fuel pressure at the fuel rail.

Have you tested the Air Flow Meter, TPS(both closed throttle and full throttle), Air Temp Sensor, Water Temp Sensor.

[Lazarus]

No pulsing on term #12 with multimeter, and therefore no pulse at injector.

No spark at plugs.

There is fuel pressure at the rail.

Water temp sensor reads 2.18 Kohm. Its good

Adjusted the TPS to click when advanced from No throttle to full throttle

I am still getting no voltage at pins 2 and 3 at EFI plug. These are the pins for the idle switch (TPS)

I will test the Air flow meter and air temp  tonight/tomorrow.

I checked my clutch switch tonight and it is broken. In neutral the bike should be able to start even with a faulty switch correct? After jumping the clutch switch connection with a piece of wire it still would not start.

[Scott_]

In neutral the bike should be able to start even with a faulty switch correct?

Yes, the clutch switch, or the neutral circuit will only prevent the starter from engaging

[rbm]

No pulsing on term #12 with multimeter, and therefore no pulse at injector.
I am still getting no voltage at pins 2 and 3 at EFI plug. These are the pins for the idle switch (TPS)

Power to both the injectors and TPI is supplied from the FI relay, located in the relay box.  Hav you tested that component for proper operation?  It's special in that it has two 87 pins, and not one as is normal for automotive relays, meaning you can't swap it with another relay in the box for diagnosis.

Does the fuel pump run for 1.5 seconds after releasing the start button?  If not, power to the fuel pump is supplied through fuse 6 from the same FI relay.

Power to the FI relay is the Red wire directly from the battery, so there should always be power on that wire even with the ignition off.  The Green/Red wires are the outputs on pins 87.

[Lazarus]

I have checked again tonight and I do have power at the TPS and pins 2 and 3 are reading correctly. FI relay is functioning correctly. Theres is also power to the injectors (same GRN/RED power supply as TPS)

I checked pins 9-10-14 according to this chart tonight. With starter running I am getting 11V on each pin instead of the indicated 1.5V - 4V.


Not sure how to address this? Thanks!

[Scott_]

Ok, I just had a DUH moment here........... Bert's chart/diagrams are for a k100, with 2 coils......... you are working on a k75 with 3.

So, pin #10 will be +12 into the ign computer from the ign/kill switch, and +12v power to the coil packs.
Pin 9, 12, and 14 will be the switched ground for the return path of the coil packs.

When you hit the starter button, the ign computer is energizing the FI relay, and the starter relay......... so the IGN computer is doing this much.
You have tested the hall sensors, and they tested ok..... but the IGN computer doesn't appear to be responding to the hall sensor inputs, as it's not pulsing the coils(pins 9, 12, and 14) or sending the signal(pin 8) to the EFI computer to enable the injectors.

Did you read any mvDC(10-20) on pin #8 when starter is turning? Without this, the EFI won't pulse the injectors.

Ok, I'm not going to make an asumption with this next question, when were taking this last set of readings for pins 9 and 14 you were "back probing" the connector with the connector plugged into the controller? 
I know that some tests need to be taken with the plug disconnected, yet some do need to have the plug connected for the proper reading. Bert didn't seem very clear on this issue.

[rbm]

I checked pins 9-10-14 according to this chart tonight. With starter running I am getting 11V on each pin instead of the indicated 1.5V - 4V.


Not sure how to address this? Thanks!

Was your multimeter on the AC scale?  That's what the "volts ~" means in Bert's chart.  11V is high for a true RMS volt reading on a vehicle, so I suspect you might have been reading DC volts.

[Scott_]

I checked pins 9-10-14 according to this chart tonight. With starter running I am getting 11V on each pin instead of the indicated 1.5V - 4V.


Not sure how to address this? Thanks!

Was your multimeter on the AC scale?  That's what the "volts ~" means in Bert's chart.  11V is high for a true RMS volt reading on a vehicle, so I suspect you might have been reading DC volts.

Robert, my train of thinking with this same question is more along the line of "was the connector unplugged" when taking the readings. If so, he would read the full voltage on all of the coil pins as the return lines on 9, 12, and 14 would still have the same voltage potential as pin 10 until they are grounded inside the IGN computer.
All that you can test/verify with reading these 4 terminals while unplugged is that the physical circuit in/out of the coil packs is good.(no open circuit) Which is a good thing to know.

[Lazarus]

Robert, the CDI was plugged in and I was backprobing when taking these readings. Very good catch with the AC voltage. I saw the ~ and read it as "somewhere around this voltage". Quite a DUH moment.

This morning I took AC voltage readings back probed on pins 9, 12, and 14. Got around 0.3V for each

Most importantly, The EFI is getting no AC voltage signal on PIN 1 for engine RPM input info. It follows that PIN 8 on CDI (engine rpm output) back probed is giving zero AC voltage reading.

I assume this can only be a result of a faulty Hall sensor although I tested accordingly. Thoughts?


P.S. I backprobed CDI Pin 2 and 3 respectively. Hall Sensor has power with and without starter running. Also has ground when starter is running

[Scott_]

So, if you are reading the .3vac(Yea, I missed the AC~ myself as well.........) on 9, 12, and 14, while the starter is turning, i would think that you should be getting spark at the plugs.

reading the 0 volts on the engine output rpm pin 8, leads me to think a bad IGN computer.

But you tried a different IGN module and still no start. Have you tried a different EFI module?
Maybe EFI pin 1 is bad/grounded so that it pulls down the output level from the IGN module, or the wire is skinned and grounded somewhere.

[Lazarus]

Correct, I have tried a different ignition computer. Have not tried a different EFI module, however im testing with EFI unplugged so I don't see how that could be the issue. I checked for shorts on the intermediate connector as well (4pin connector between CDI and EFI)

I have ordered a new Hall effect sensor and heres why...

Just performed the LED test again on the hall sensor and was not getting on/off of the LED when gap was obstructed / unobstructed. The difference between this test and my previous test was that I changed the polarity of the leads powering the HES.

Down at my HES...
   The two black wires from the sensors connect to a RED lead to the CDI plug
   The two red wires from the sensors connect to a BLACK lead to the CDI plug

This struck me as odd and initially I trusted the colors coming off the sensors instead of the leads going into the computer. Doing this, the sensors checked out as functioning.

This time I trusted the plug lead colors and supplied (+) to pin 2 and (-) to pin 3.

Sorry if this is convoluted.

[Scott_]

No apolgies needed.
When I first got my BMW it took me the longest time to remember that brown is negative/ground.