A different kind of startus interruptus

[Earl Bowman]

...although a starter issue shouldn't let me crank it over by shorting out the solenoid?

 

[Earl Bowman]

...although a starter issue shouldn't let me crank it over by shorting out the solenoid?

Maybe burned or dirty contacts in the solenoid causing too much resistance so the ECU shuts it down?

 

[pswiatki]

Just because the battery is relatively new, doesn't mean it is good. If the battery isn't prepped correctly, it won't last long. Guzzi even put out a service bulletin on the issue Once acid is installed into a new battery, it must sit at least 3 hours (I like about 12 hours to be sure) for the acid to fully permeate the glass mat before charging. Also the battery should be fully charged before going into service to have the expected service life. So, take the battery out and have it load tested. If good, check for a parasitic drain.

All true. I bought the battery dry with the electrolyte in a separate container (all from YUASA, of course). Followed their instructions and recommendations, so the battery was properly prepped, I think. I shall check the parasitic drain. Will report back when I have any results.

 

[Kevin.NZ]

I don't think its a good idea to smear the plunger with light oil as it will cause dust from the clutch to adhere, use dry graphite. Most (car) ECU's wont operate below 10 volts but this is overridden during cranking. A decent battery is still required.

 

[pswiatki]

I don't think its a good idea to smear the plunger with light oil as it will cause dust from the clutch to adhere, use dry graphite. Most (car) ECU's wont operate below 10 volts but this is overridden during cranking. A decent battery is still required.

Question is: does the ECU have any internal voltage threshold that, when crossed, would shut off the ECU and cause the crank cycle to be aborted (because the starter relay would open its contacts).

 

[V700Steve]

I've been bypassing MG's system for over 40 yrs. If you put a meter on batt and hit the switch does it go under 12V when starter engages? How much does it drop?

 

[pswiatki]

For some reason I don't see the screenshots I put in my previous posts. They show how deep and for how long the voltage drops before recovering back to [let's say] normal level. The lowest can be below 6V. and yes, this is the voltage measured at the battery terminals. By the way: the meter will never show you this, only the oscilloscope, which is way faster in its measurements.

 

[V700Steve]

I can see them, just means their engineers fail in long run. I asked Tech Rep about Startus Interuptus in 09 and he said it's not guaranteed to start if it goes below 12V. Most good batts are 13.2 at least. When you hit the start it goes to 10V.
Just too much junk in the wiring is why I would never own anything past 2005
For 1 thing the starters came from era we used 32AH batteries not 20-18. I still run 34AH batts in all my Guzzi's.

 

[pswiatki]

What do you mean when you say that voltage drops to 10V during the crank? I see a problem with the measurement technique. I know that using an oscilloscope is probably a bit misleading as it shows the "momentary" level of the voltage while the multimeter will show you some average value (RMS, etc.). I would say different meters could do the averaging a bit differently and show different results during the startup cycle. Moreover, it is short enough for the meter to show the lower result for a short time only. It can be seen in my screenshots - the deep part of the drop (even on a good battery) is very short, however, the voltage remains at the lower [than ~12V] level for some time. That is: until the ECU decides the engine is spun enough to disengage the starter. Then the voltage regulator kicks in and the level goes up to whatever the alternator provides.
My experience was that the crank cycle was aborted during the phase when the drop was the deepest.
So, I imagine the ECU disliked the drop so much so it shut down completely (thus releasing the startup relay).

 

[GTM®]

Maybe burned or dirty contacts in the solenoid causing too much resistance so the ECU shuts it down?

There's a few threads here on (aged bikes) sticky solenoids. Try a search and clean or replace is where I'd start.

What do you mean when you say that voltage drops to 10V during the crank?

I can't recall where I heard this, but the CARC bike's ECUs all will disable the start sequence if the voltage drops below 10.7v on demand of the starter motor.

 

[pswiatki]

I can't recall where I heard this, but the CARC bike's ECUs all will disable the start sequence if the voltage drops below 10.7v on demand of the starter motor.

Ok Todd, good to know. I wonder how the ECU measures the voltage because setting this threshold so high is problematic as far as I can see, so some averaging would have to be done to keep the result high enough for 10.7V to be the adequate value. Not sure what you mean by "on demand of the starter motor" - could you explain?

 

[GTM®]

Ok Todd, good to know. I wonder how the ECU measures the voltage because setting this threshold so high is problematic as far as I can see, so some averaging would have to be done to keep the result high enough for 10.7V to be the adequate value. Not sure what you mean by "on demand of the starter motor" - could you explain?

If you pull the voltage up on the dashboard screen, that is what the ECU sees. Pressing the start button, if the ECU sees 10.7v or less, it will not energize anything.

 

[pswiatki]

Oh, I see. This makes sense. Something (cluster?) is monitoring the voltage and producing the result, other modules (I guess in MG it would be lone ECU or maybe - where present - ABS, too) read it and evaluate for their purposes. So, yeah: 10.7 is ok if used like that. Thank you for the explanation.

By the way: is my browser bad, or what could be the reason I cannot see the pictures I attached to my previous posts in this thread? Other users say they can see them without any problems. My browser is Chromium 81.0.4023.0. I shall try something else to see if things get better.

 

[pswiatki]

Microsoft Edge works better. Problem solved.

 

[V700Steve]

Impressed on the readings from the scope, I use a digital multi meter. I had no idea it dropped that low. I can understand how it confused the ecu w/a hotwire . Not part of it's program.

 

[pswiatki]

Yes, it will drop looow. I think the situation with the stationary starter and the current flowing is very close to a short circuit on the battery. Thus, current goes really high and voltage drops fast. The good thing is that as soon as the starter motor starts cranking the engine current drops and voltage on the battery recovers (but holds on at some lower than idle value - after all the starter still draws significant current). DMM reading would be some average of the curve you can see in the screenshot from the scope. Would the result on the DMM will be the same as on the dashboard? Hmmm... who knows...
I guess the ECU should survive the deepest phase of the drop (if the level isn't critically low), but if the value reported by the DSB is lower than some threshold (10.7V - as Todd said), the ECU may abort the crank cycle.

 

[scottmastrocinque]

Virtually every weird starting and dashboard errors which I have encountered on my Moto Guzzi's, Ducati's, BMW's and even my Ural, can be traced back to substandard battery performance. Modern ECU's are very voltage sensitive and relays, both solid state and mechanical, do not like substandard voltage. Running electricity across a relay that is less than required for normal operation, causes "bouncing" of the relay and electrical circuit and this is as destructive as "pinging" in a combustion engine.

Hence, the limiting function Todd describes above, whereby the ECU will shut down the starting sequence to protect itself and the relays and circuit in general.

Many Stelvio owners have discovered the frustrating experience of having cranked over a bad battery Stelvio, only to hear the rapid fire clicking of the relay, until it suddenly goes completely silent. Later, after they change out or charge the battery, their headlights stop working correctly and this is because the relays have fused or burned the contacts.

I find it useful to keep in the front of my brain, the fact that ECU switches, and relays are designed for one purpose, to allow a small electrical charge, to regulate the engagement or cessation of a much larger electrical charge. When things start going whacko, or behaving bizzare, invariably I discover that poor electrical supply in either the battery itself, the ground strap, or even wiring loom damage, is the culprit.

I also stumbled upon this little bit of relay trivia which I have found helpful. It's the DIN (Deutsches Institut für Normung) nomenclature used on relays which has been adopted virtually all over the world now.

Motorcycle Relay Terminal Codes

The German Institute for Standardisation (DIN) created the standard DIN 72552 for the labelling of automotive electrical terminals. Over time, this standard has been adopted industry wide. Today, almost every electrical contact on a motorcycle has been standardised with a numerical code.

Here’s a list of the DIN 72552 numerical codes that relate to motorcycle relay devices:



Relay coil terminal codes

• 85 = V+
• 86 = V-

Electrical contact terminal codes

• 87 = contact common
• 87a = normally open contact
• 87b = normally closed contact

Additional relay terminal codes

• 88 = 2nd contact common
• 88a = 2nd normally open contact
• 88b = 2nd normally closed contact

 

[pswiatki]

Virtually every weird starting and dashboard errors which I have encountered on my Moto Guzzi's, Ducati's, BMW's and even my Ural, can be traced back to substandard battery performance. Modern ECU's are very voltage sensitive and relays, both solid state and mechanical, do not like substandard voltage. Running electricity across a relay that is less than required for normal operation, causes "bouncing" of the relay and electrical circuit and this is as destructive as "pinging" in a combustion engine.

Hence, the limiting function Todd describes above, whereby the ECU will shut down the starting sequence to protect itself and the relays and circuit in general.

I agree. The observation of how things happen during crank and experiments show this sensitivity of the ECU. When activated externally, the startup relay does not show any bouncing issues or any other suspicious behaviour. Crank is done as expected. This leads me to believe that perhaps the ECU is hyper-sensitive where it maybe doesn't have to be. Since the crank sequence is commenced by the ECU after it detects the starter switch activation it surely has to prepare for the voltage drop prior to relay activation. After some time (milliseconds) the ECU resumes voltage monitoring and it should be able to function (unless the battery is depleted to a point where the power supply is truly insufficient). So, the question really becomes this: are the thresholds (voltage level, time) set the way they should be, or they (Marelli, maybe MG, too) wanted to be on a safe side and set up those thresholds rather conservatively.
Given your example:

Many Stelvio owners have discovered the frustrating experience of having cranked over a bad battery Stelvio, only to hear the rapid fire clicking of the relay, until it suddenly goes completely silent. Later, after they change out or charge the battery, their headlights stop working correctly and this is because the relays have fused or burned the contacts.

and possibly that they knew the wire harness/ground connection, etc. may be problematic in their bikes - they may have done the ECU setup (for voltage monitoring, etc.) in a way that feels very sensitive, indeed.

I have to check my SD cards and pen drives. I may have scope screen captures from good cranks after I charged the battery. I wonder if the "recovery" level after the deepest drop was higher than the level before the battery was charged. It would be quite interesting to know. I shall come back here when I find any info on that.

 

[Earl Bowman]

UPDATE: Almost 6 months after my starting problems began, a follow up on my startus interuptus issues. "Check your battery" they said, "Probably your battery" they said, "Have you tested your battery?" they asked. Well, yes! I checked voltage on the battery with my multi-meter staic and during starting, I checked it with the onboard voltmeter screen, I checked voltage at the starter during starting. I checked the battery with my battery load tester. ALL of the tests checked out fine. 13.0 - 13.2 volts. Well, after checking virtually every electrical connection and pin I could find on the bike including the MPH Cycles relay wire around harness, after replacing all the relays and the starter, after replacing all the fuses, after cleaning and deoxiting the starter button, after taking a scotchbrite pad to all the terminals and cable ends until they shined like a new penny, I gave up! I put in a new battery, Boom!, starts every time now! Let the "I Told You So's" begin! After nearly 6 months I'd almost forgotten the things I loved about this bike...memory refreshed!

 

[Kevin.NZ]

Ha ha , let me be the 1st--I told you so