Early Griso Startus Interruptus

[Kiwi_Roy]

I thought I would investigate the new to me 2007 GRiSO to see if it would benefit from the Startus Interuptus fix.
As you probably know the ailment is caused by wiring that is not able to deliver the current the starter solenoid would like.
The solenoid if its allowed to will draw over 40 Amps literally throwing the cog's into mesh with a resounding clunk.
Unfortunately due to an oversight at the factory the wiring is not up to the task. it usually finds a weak spot, Ignition switch, relay base or weak wire along the way which effectively throttles the current I used to think the main culprit was the ignition switch however today I discovered the tiny wire on the GRiSO from the Start Relay to the solenoid, I doubt they could have found a smaller wire if they tried.
I did a test on the wire to see how much Voltage it would lose at 40 Amps, it calculated out that it would drop 1.8 Volts
Add to this the resistance of the supply, relay contacts/relay base and it soon adds up.

Next step is to take some measurements to determine how the starter is working, I did some time and current measurements using an oscilloscope.
When you press the start button a heavy current pulse from the start relay pulls the solenoid into the core engaging the gears. The heavy current pulse lasts until the main contacts close.
At this point the battery Voltage is applied to the motor and it draws well over 150 Amps, the motor starts to turn and the solenoid current drops to about 10 Amps.

I measure this time and I find the solenoid pulse lasts for 50 milliseconds while the solenoid current peaks about 22 Amps which is ok but not great.

So then I upgrade the wire from the relay to the solenoid. The current pulse now lasts only about 15 milliseconds, less than 1/3 as long telling me the solenoid is operating at three times the speed it was before and the current peaks just over 30 Amps

Note: This current I am referring to is not the cranking current, it's just the current into the solenoid.

I have a storage scope but it's quicker just to sketch out the trace. I drew Before and After on top of each other for comparison.
You can see what a huge difference it made when I replaced Luigi's little bitty wire (Red Trace) with an 18 gauge wire (Green Trace)
 
Interestingly after the fix although the current is much higher the solenoid expends less than half the energy it did before



The modern schematics don't even show one coil for the starter solenoid, how's an owner supposed to figure that out?

This is how the starter solenoid should be drawn, with two coils. (The names or the coils are mine)

The two coils work together to pull in the solenoid
The Holding coil pulls about 10 Amps
The Pull In coil would pull over 30 Amps if it had decent wiring,but instead they only pull about 22 Amps combined through the wimpy wires as I show in the sketch above (red trace)
When the main Contact closes the Pull In coil now has the same Voltage at both ends so it's current drops to zero and the Hold In coil keeps everything in place with
it's 10 Amps and the bike starts to crank as the motor receives the full current from the battery.

When you take your finger off the button the spade connector (blue wire) no longer has Voltage and the current runs backwards through the two coils in series but now the coils work against each other cancelling the magnetic attraction letting the solenoid spring back open.

[Kiwi_Roy]

Compare the difference between a 2006 and 2008 Griso wiring courtesy of Carl's excellent drawings
Here is the 2006 Start Relay fed direct from fuse "C" (strictly speaking through 2 fuses in series) to relay (3) and back to the solenoid.
http://www.thisoldtractor.com/guzzi007/schematics/2006_Griso_1100.gif

And the 2008 from the main fuse up to the ignition switch down to fuse 2 to relay (2) and (3) and back to the solenoid
http://www.thisoldtractor.com/guzzi007/schematics/2008_Griso_8V.gif

I would hazard a guess and say the later one will have more problems as the wiring and components start to age.

The modern schematics don't even show one coil for the starter solenoid, how's an owner supposed to figure that out?

I'm sure the Griso shares much in common with the other CARC models.

[Wayne Orwig]

When I first encountered this, I put a resistor in place of the solenoid. I measured the drop through each part of the circuit. I was surprised at how much voltage drop there was in the Norge I was working on. It was only getting about 6 volts to the solenoid. And the fact that there are TWO fuses in the line, and the voltage drop across those, did not help. I lost those numbers long ago. but the wire from the relay down to the solenoid was wimpy for sure. But the wiring up through the ignition switch and back was the worse. You fix that and you can live with the wimpy wire to the solenoid.

[Kiwi_Roy]

When I first encountered this, I put a resistor in place of the solenoid. I measured the drop through each part of the circuit. I was surprised at how much voltage drop there was in the Norge I was working on. It was only getting about 6 volts to the solenoid. And the fact that there are TWO fuses in the line, and the voltage drop across those, did not help. I lost those numbers long ago. but the wire from the relay down to the solenoid was wimpy for sure. But the wiring up through the ignition switch and back was the worse. You fix that and you can live with the wimpy wire to the solenoid.

I found out about the second coil messing with my 01 VII Sport, I Ohmed out the solenoid, Lo and Behold it seemed like a dead short. 1.05 and 0.25 in parallel
The 01 would never suffer from Startus Interuptus because the solenoid circuit was battery, fuse, relay, solenoid, the inrush current was well over 40 Amps
The 07 Griso is similar wiring (not through the switch) except the wires are much smaller
The 08 Griso is back to the old wiring through the ignition switch.

I really think the factory measured the current and saw <10 Amps then sized everything accordingly, 15 Amp fuse, 10 Amp wires, they missed the inrush current which only lasts a few milliseconds.
You measured about 6 Volts, just 50% of whats available.

[Kiwi Dave]

The 07 Griso is similar wiring (not through the switch) except the wires are much smaller
The 08 Griso is back to the old wiring through the ignition switch.

I'm flabbergasted that the 07 Griso is not the same as the 08 Griso, or all CARC models since the Breva 1100 debut in 2005 (where I'm from, other country's might have got them a little earlier).

Roy, can you elaborate how you know this, or are you just looking at a particular 07 Griso that might have been modded before you initially saw it?  In other words, why would the factory get it right just for one year?

[jacksonracingcomau]

I'm flabbergasted that the 07 Griso is not the same as the 08 Griso, or all CARC models since the Breva 1100 debut in 2005 (where I'm from, other country's might have got them a little earlier).

Roy, can you elaborate how you know this, or are you just looking at a particular 07 Griso that might have been modded before you initially saw it?  In other words, why would the factory get it right just for one year?

He posted links to wiring diagrams, why does anyone go 3 steps forward and 5 back? just the way it is
But this problem on and off since first electric start, how the 70's bikes got out with no fuse on the ignition circuit more odd.

Easy fix, well written Roy

[Kiwi_Roy]

I'm flabbergasted that the 07 Griso is not the same as the 08 Griso, or all CARC models since the Breva 1100 debut in 2005 (where I'm from, other country's might have got them a little earlier).

Roy, can you elaborate how you know this, or are you just looking at a particular 07 Griso that might have been modded before you initially saw it?  In other words, why would the factory get it right just for one year?

As JRC said from Carl's wiring diagrams
My 2007 2 valve has a single Start Relay (3), the 2008 4 valve has a Start Relay (2) and an additional Start Maintenance Relay (3)
I have no idea why they added a relay and changed the wiring, I suspect to cure a problem they caused earlier, I'm sure the 2008 will start without the second relay (3)


Question,
My 2007 will continue cranking until it starts or I turn the key off, are the 2008 the same?
Has anyone experienced a problem with either 2006 or 2008->  CARC starter latching On until the battery is disconnected or runs flat?

[Moto]

Question,
My 2007 will continue cranking until it starts or I turn the key off, are the 2008 the same?
Has anyone experienced a problem with either 2006 or 2008->  CARC starter latching On until the battery is disconnected or runs flat?

Nice work, Roy!

My 2007 Griso also keeps the starter engaged until the motor starts, whether or not the button is released. That's standard. I've never had the starter latch on in the way you asked about.

I've never had any particular problem starting unless I let the battery discharge by sitting for weeks. I've never bothered with a startus interruptus fix.

I wonder if there is any chance that the greater acceleration of the meshing gears implied by your green trace could damage them over time. Maybe the Guzzi engineers are geniuses and specified the tiny wire just to prevent that.

Maybe not.

Moto

[Idontwantapickle]

Question,
My 2007 will continue cranking until it starts or I turn the key off, are the 2008 the same?
Has anyone experienced a problem with either 2006 or 2008->  CARC starter latching On until the battery is disconnected or runs flat?

If the engine fails to run the ecu will discontinue the start sequence automatically after a certain time. That’s how mine works.
You may have more sympathy for the starter than the ECU!

[Kiwi_Roy]

If the engine fails to run the ecu will discontinue the start sequence automatically after a certain time. That�s how mine works.
You may have more sympathy for the starter than the ECU!

Are you referring to a 2007 2 Valve Norge?

[Phang]

from my understanding of the wiring diagram

the second relay (maintenance relay) will allow the owner to continue cranking the engine by holding down the Start button, in the case of ECU detected a low battery voltage and quit in the beginning or midst of the auto crank sequence

as Kiwi Roy said earlier, a patch work to cure a problem that they created

[Kiwi_Roy]

from my understanding of the wiring diagram

the second relay (maintenance relay) will allow the owner to continue cranking the engine by holding down the Start button, in the case of ECU detected a low battery voltage and quit in the beginning or midst of the auto crank sequence

That makes sense Phang  , but they could have done that with a software fix instead. I work with industrial Programmable Logic Controllers that allow you to change logic like that.
It would be interesting to see the logic, does GuzziDiag gives you access to that?

[Phang]

That makes sense Phang  , but they could have done that with a software fix instead. I work with industrial Programmable Logic Controllers that allow you to change logic like that.
It would be interesting to see the logic, does GuzziDiag gives you access to that?

I have no idea regarding GuzziDiag, Roy

my brain and eyes hurt after focusing on the wiring diagram on laptop screen 

I have the same question too, can't they just lower the voltage threshold in the ECU autostart logic?

maybe it is more than 'just a few clicks' on the programmer and adding a 'maintenance relay' was an easier fix

[Wayne Orwig]

That makes sense Phang  , but they could have done that with a software fix instead. I work with industrial Programmable Logic Controllers that allow you to change logic like that.
It would be interesting to see the logic, does GuzziDiag gives you access to that?

That would be in the dashboard logic, not the ECU. Guzzidiag only reprograms the ECU.

[Phang]

That would be in the dashboard logic, not the ECU. Guzzidiag only reprograms the ECU.

most of the inputs for safety/startup logic are wired to the ECU (side stand, neutral, bank angle sensor, clutch switch, kill switch, Start button), the sole output (start-up relay) also connected to the ECU

key antenna, required in startup logic, is connected to the dashboard

Although it is entirely possible that the control logic is resided in the dashboard, I am more inclined to believe that the ECU makes the call here

[Kiwi_Roy]

I have never seen a logic diagram, the logic of course could be in the dash but as Fang says the I/O is in the ECU, the indication of status is on the dash of course via CanBus.

Who knows where the logic resides, at least it's not on the cloud yet so we have a fighting chance.

There must be a drawing of the logic somewhere, it would be good to get our hands on a copy.