citroen c3 'decides' it doesn't want to start

[chris dobo]

I am staggered that something as straightforward as operating a starter solenoid should be totally unnecessarily complicated by use of a CAN bus...

Madness...

There is a line from the ignition switch to both the BSM and the BSI (at the start position). I surmise that the starter relay is not directly driven by actions from the CAN BUS. However I do know that the relay (R8) is driven from the electronics of the BSM and not directly by that ignition switch wire. I have a member over on the C3 forum that (co-indecently) has a C3 where the starter will engage, randomly, without the key even being in the ignition lock!!
Could be an interlock to stop the starter engaging while the engine is running? I know that the BSM cuts power to the fuel pump if the engine stops running (from data over the CAN BUS). So it's not a big stretch to think the BSM stops the starter relay if the engine is running. I have the CAN-VAN platform so I cant experiment. Oh...and it could stop the ignition switches burning out too!

The only fly in my "theoretical ointment" is; why would the BSI need to know when the engine is cranking (I.E. the ignition switch is turned to 'start')? In the CAN-VAN cars the BSI is not connected to the 'start' contacts of the ignition switch! I know that there are a lot of "cross checks" done between the BSM and BSI on the all CAN systems that are not done on the CAN VAN cars?!

i did find the wire going to the starter solenoid was live at one point when ididn't even turn the key. It made absolutely no sense. It was at this point I stopped and realised I had no idea how the system worked.

[chris dobo]

I am staggered that something as straightforward as operating a starter solenoid should be totally unnecessarily complicated by use of a CAN bus...

Madness...

There is a line from the ignition switch to both the BSM and the BSI (at the start position). I surmise that the starter relay is not directly driven by actions from the CAN BUS. However I do know that the relay (R8) is driven from the electronics of the BSM and not directly by that ignition switch wire. I have a member over on the C3 forum that (co-indecently) has a C3 where the starter will engage, randomly, without the key even being in the ignition lock!!
Could be an interlock to stop the starter engaging while the engine is running? I know that the BSM cuts power to the fuel pump if the engine stops running (from data over the CAN BUS). So it's not a big stretch to think the BSM stops the starter relay if the engine is running. I have the CAN-VAN platform so I cant experiment. Oh...and it could stop the ignition switches burning out too!

The only fly in my "theoretical ointment" is; why would the BSI need to know when the engine is cranking (I.E. the ignition switch is turned to 'start')? In the CAN-VAN cars the BSI is not connected to the 'start' contacts of the ignition switch! I know that there are a lot of "cross checks" done between the BSM and BSI on the all CAN systems that are not done on the CAN VAN cars?!

When i was trying everything I could think of with an electrical circuit tester i did notice a wire that went to the soleniod was actually live when i didn't even have the key in the ignition. It didn't actually switch the stater motor on thoough for some reason. I think it was at this point I gave up as I realised I was dealing with forces that defied all my logic and i was out of my depth.

[CitroJim]

I think it was at this point I gave up as I realised I was dealing with forces that defied all my logic and i was out of my depth.

I feel for you Chris... I know exactly just that

[ozvtr]

Here is the circuit diagram of the starting and generating circuit (thanks to Marc and a previous post).
I believe the line drawing of the ignition switch (C001) is incorrect. So ignore it for the time being.
In the ignition 'start' position, pin 6 of the 10pin WHITE connector of the BSI, and pin 9 of the 28pin GREEN connector of the BSM (PSF1 in the diagram) have 12V power applied to them from the start contacts of the ignition switch (trust me).
If the BSM is happy, the coil of R8 is grounded (by the electronics of the BSM) and it's power contacts close. Current can now flow from the battery positive, through fuse F8 in the BSM, through the power contacts of R8, out pin2 of the 5way yellow connector of the BSM, to the starter solenoid positive contact, through the solenoid to engine ground. Yes, I know that the electrons don't flow that way...but it's less confusing!

So, my first point to check would be pin9 of the 28way GREEN connector of the BSM. This should have 12V ONLY when the ignition switch is turned to 'start'.

[chris dobo]

Here is the circuit diagram of the starting and generating circuit (thanks to Marc and a previous post).
I believe the line drawing of the ignition switch (C001) is incorrect. So ignore it for the time being.
In the ignition 'start' position, pin 6 of the 10pin WHITE connector of the BSI, and pin 9 of the 28pin GREEN connector of the BSM (PSF1 in the diagram) have 12V power applied to them from the start contacts of the ignition switch (trust me).
If the BSM is happy, the coil of R8 is grounded (by the electronics of the BSM) and it's power contacts close. Current can now flow from the battery positive, through fuse F8 in the BSM, through the power contacts of R8, out pin2 of the 5way yellow connector of the BSM, to the starter solenoid positive contact, through the solenoid to engine ground. Yes, I know that the electrons don't flow that way...but it's less confusing!

So, my first point to check would be pin9 of the 28way GREEN connector of the BSM. This should have 12V ONLY when the ignition switch is turned to 'start'.

Thank you so much that's incredable. Thats so kind of you to go to so much trouble to gather all this information. As soon as I get the time to use this i will let you know what i doscovered.

Thanks again

[ozvtr]

Thanks again

You are most welcome.

My guess is that you get nothing from pin 9 of the BSM (when the car refuses to start). But then again, I shouldn't preempt your results.

[Coldxzero]

Guys pleaseee I am from Oman also i have C3 2007 1.6 L i have tge same issue since 5 days i read one reply that its causes because of transmission its not on park or nutral, I think its the problem because I was try to move gearbox selector under air filter and gear cabled moved then its unable to start also battery light on dash board start blinking so I thing I think its the issue but how to solve this issue i dunno, i am so tired how to solve that issue

[Coldxzero]

Chris, you'll need to consult a wiring diagram to see how the solenoid is fed... I can't imagine it's as clever as we'd like to think it might be!

This very issue was once very common on some V6 Xantia and XM models and it was down to high-resistance contacts on the ignition switch...

Another potential cause, if it's an automatic, is the start inhibit circuitry which prevents a start if the transmission is not in park or neutral.

Given a donation and your VIN Number forum staff may be able to offer you a wiring diagram... All should then look a little clearer...

Guys its true i try to move gearbox selector under air filter then the car unable to start again any solution