c5 3lt v6 2006 not starting

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garycanfix
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c5 3lt v6 2006 not starting

Post by garycanfix »

Hi and thank you to all that will help, My brother got this car> c5 v6 3lt auto last year, car was overheating when stud or at lights for a long time, he was told it was the fan so he took the front end of the car and put power down to the fan from the battery to test the fan with 12v, but what he as done is put power to all the wires that run down to the fan to try and get it to spin, upon doing this is car will not start ( dead will not turn over) the starter moter is ok as i have put 12v to it and it turns ok but will not turn with the key, you can hear the relay click under the dash when you turn the key, RAC man says no coms to ecu, my brother sent the ecu off to have it checked (£60) all is ok with that, but the RAC man says it may be the BSI unit as well, dose any body know if the starting goes through the BSI, i think he as shorted some think out by puting 12v to all the wires at the front near the fan,(yes the two thin wires that go to the relay as well). 3 weeks and still no idea. Please if and body can help.
Gary
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Re: c5 3lt v6 2006 not starting

Post by DHallworth »

Can't be much help I'm afraid. Putting 12v to everything when not knowing what they are is a dangerous way, and potentially very expensive way of testing things though :(

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Re: c5 3lt v6 2007 not starting

Post by garycanfix »

Thanks i am in thurnscoe rotherham, forgot say it is a auto and it dose say "gearbox faulty" when you turn the key on, he as sent the bsi off and they say it was coruped, reloaded the software and sent it back, we marride it back to the car with lexia 3, vin code etc etc but still doing the same 4 weeks now and pulling hair out.
dose any body know the relay or the wireing from when you turn the key to it getting to the starter, may be i could follow the 12v and find out when it stops, any help at all please tottel cost up to now is £350.
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Re: c5 3lt v6 2006 not starting

Post by Stickyfinger »

You really need to get this under the eye of a qualified auto electrician...........messing about with a Citroen's electrics is NOT a good thing to this level unless you have all the correct equipment.
Any help here will be a pure guess and is NOT the way to help you...likewise "swapping" parts is not really the correct approach to the problem either.

ALL modern car electronics are highly sensitive to back feeding the wrong current.....would you expect a PC to survive if you wired it the wrong way ?
On this, most people will struggle
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Re: c5 3lt v6 2006 not starting

Post by wheeler »

I'm assuming you have checked ALL the fuses on the car ?? inside and under bonnet ?
If they reckon the ECU is ok but there is no communication with the ECU with Lexia then that suggests the ECU is missing a power supply or earth somewhere. You really need the injection system wiring diagram to check the supplies to the ECU first before going any further, I assume you can't hear the fuel pump priming either ?
The most likely reason for ECU power supplies being missing on this car is a failed under bonnet fuse box, the main injection supply relay and the starter motor relay are both an integral part of this. I must stress that is a guess based on what you have said & without getting hands on & doing further checks.
I wouldn't be thinking BSI at this point.
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Re: c5 3lt v6 2007 not starting

Post by wurlycorner »

garycanfix wrote: dose any body know the relay or the wireing from when you turn the key to it getting to the starter, may be i could follow the 12v and find out when it stops, any help at all please tottel cost up to now is £350.
Is the 'typical starting circuit' on page 12-23 of Haynes no use to you?
That's where I'd start.

Looking at that diagram, it suggests that as far as operating the starter motor it's nothing more complicated than on an 'old' car - which is entirely what I'd expect for this circuit (unless you car has automatic engine start/stop at traffic lights etc. in which case electronics and relays will be involved...). I'm not familiar with what equipment an 08 plate C5 has on that front...

That being the case (and with reference to the Haynes diagram) there is nothing more involved than battery, fuse MF7 in the engine fusebox, ignition switch ('start' contact position), a straight link back through the engine fusebox and the starter motor itself.

If you've tested the starter motor directly, then check the fuse indicated (check for resistance across the fuse also, not just continuity in case it's gone high resistance) and also check that the straight link through the fuse box is also good. Then check for continuity across the start position on the ignition switch (if testing dead i.e. with battery disconnected) or check for 12v out of pin 3 (so it says) on the igntion switch (if testing live).

Other than that, you're then tracing the wiring through for any breaks.

My assumption is that the relay you can hear click, is the injection/fuel pump relay, rather than anything to do with the starting circuit (unless X7's have automated start stop, as I mentioned earlier, in which case the circuit will be different).
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