S4 Intermittent Start

[ozs4]

Hi,
I am having some intermittent start issues with my S4.  Occasionally it will not turn over, but will start if the solenoid is shorted.  The starter button and solenoid checks out OK.
Am I correct in thinking that the immobilizer only inhibits the starter and not the ignition?  What indication should I get from the flashing LED on the tacho if the immobilizer is good?

Thanks in advance

[Capo]

The imobiliser shuts off everything.
I have encountered this problem before, on the S4 it is mounted on the front of the airbox, moisture gets in and the contacts corrode.
Burnish the contacts, contact cleaner then dielectric grease.

[Speeddog]

Starter relay is controlled directly by the ECU.

The ECU looks at the sidestand switch, clutch switch, and neutral indicator to see whether it's safe to engage the starter.

Which year of S4 is it?
There is a difference in the 'logic' criteria that the ECU uses.

[Jobu]

Rameses S4 was doing the same thing.  It would turn over with the solenoid shorted but wouldn't turn over when wired normally.  He replaced the solenoid and it still didn't work.  Then he set it on fire.  Now it starts every time and looks like a Hypermotard.

[ozs4]

Starter relay is controlled directly by the ECU.

The ECU looks at the sidestand switch, clutch switch, and neutral indicator to see whether it's safe to engage the starter.

Which year of S4 is it?
There is a difference in the 'logic' criteria that the ECU uses.

Its a very early 01 model.  Sidestand is bypassed, and there is definitely no clutch switch, and I am fairly certain there is no neutral switch on this model.

[ozs4]

Rameses S4 was doing the same thing.  It would turn over with the solenoid shorted but wouldn't turn over when wired normally.  He replaced the solenoid and it still didn't work.  Then he set it on fire.  Now it starts every time and looks like a Hypermotard.

Sounds drastic, but I like your thinking.

[ozs4]

The imobiliser shuts off everything.
I have encountered this problem before, on the S4 it is mounted on the front of the airbox, moisture gets in and the contacts corrode.
Burnish the contacts, contact cleaner then dielectric grease.

Thanks.  I will give it a go.

[Speeddog]

Its a very early 01 model.  Sidestand is bypassed, and there is definitely no clutch switch, and I am fairly certain there is no neutral switch on this model.

No clutch switch 
Was it removed?
AFAIK, they all came with one...

The ECU piggybacks off of the neutral light wire.

[ozs4]

No clutch switch 
Was it removed?
AFAIK, they all came with one...

The ECU piggybacks off of the neutral light wire.

Its an ex race bike, so I am assuming that it has been removed by the previous owner.  I'll check the loom.

You would have to be a rocket surgeon to work out the ducati wiring diagram.

Thanks for your help.

[Speeddog]

Yeah, check to make sure that however the clutch switch and sidestand switch have been defeated isn't intermittent.

Especially the sidestand switch 'defeat', because if the ECU thinks the stand is down, it won't start.

[ozs4]

The imobiliser shuts off everything.
I have encountered this problem before, on the S4 it is mounted on the front of the airbox, moisture gets in and the contacts corrode.
Burnish the contacts, contact cleaner then dielectric grease.

Thanks.  I will give it a try tommorrow.

[Howie]

Do keep in mind you will need to trouble shoot when the bike is not starting.  There is a connector with two small wires on the back of the solenoid.  One should be getting battery voltage when you hit the starter button.  If so, either the connection is poor or you need a solenoid.  No voltage?  Then the problem is in the control circuit starter (button, kill switch, ignition switch, ECU, sidestand switch, clutch switch, related wiring and I probably forgot an item or two).

I didn't know '01 S4s had a clutch switch.

[ozs4]

Do keep in mind you will need to trouble shoot when the bike is not starting.  There is a connector with two small wires on the back of the solenoid.  One should be getting battery voltage when you hit the starter button.  If so, either the connection is poor or you need a solenoid.  No voltage?  Then the problem is in the control circuit starter (button, kill switch, ignition switch, ECU, sidestand switch, clutch switch, related wiring and I probably forgot an item or two).

I didn't know '01 S4s had a clutch switch.

Don't know if it had a clutch switch originally, but it hasn't now.

The solenoid is good.  I have removed it and tested with 12 volts, works everytime.  I am getting 9 volts at the solenoid connector when the button is pushed, but if I connect the solnoid and check the voltage with it connected it drops to zero.  Thinking there is a high resistance in the wiring, or  the ECU has developed a fault and can't supply the load.

[ozs4]

I enlarged the diagram and had and had good look through it this morning.  From what I can see, the ECU is independant of starter solenoid operation.  The circuit flow is as follows:

12 volts is fed from the immobilizer to the ignition key
Ignition key switch feeds 12v to the key sense fuse (also energises the ignition relay, before the fuse)
12 volts from the fuse to the starter button
12 volts from the starter button to the solenoid
ground from the starter solenoid via the side stand (also fed to the ECU) switch to the battery

Given that the ignition is working as advertised, this proves that the immobilizer, ignition switch and fuse are all good.

This leaves either a wiring fault, faulty starter switch or fault side stand switch shorting plug.  Should give me something to do over the Christmas break.

Thanks for all your advice so far.

[Speeddog]

Strike what I said before on the clutch switch on an '01 S4. 
They don't have one, at least according to the wiring diagram.

And the starter solenoid is controlled directly, not by the ECU.
It *is* dependent on the sidestand switch for grounding, or the ECU if the sidestand switch is open.
At least that's how it appears...

I'd thought the '01 S4 wasn't as different from the '02.

Learn something new every day, if I'm lucky.