Ignition Fault

Well back to the drawing board as the ECU's were sent off to the ECU Doctor and came back with no fault found ?. So with working TDC sensors, working ECU's, coils tested & correct voltage when starting, I am at a lost as to where to check next. It had a similar fault when I first got her 7 years ago. I then tracked it down to a faulty starter motor (it would spin correctly and the coils were getting >10v) but wouldn't start. I could only guess that when they delivered it (I know they tried to jump start it) they got the polarity wrong and damaged the starter motor, so maybe the AA engineer damaged the starter motor again when he shorted the HT side of the coils.

 

Well today I installed the Digiplexes, bridged out the alarm and again no start. So plugged alarm back in again and noticed that I had forgotten to reinstall the relay for the fuel pump (I had removed it when testing using the scope last week). Once I plugged in the relay she fired up. Great so I thought, so I reinstalled the Digiplexes and dash cover for the fuses, tried to start again and no start.
So I removed the Digiplexes from the well and swapped over the relay again without any success. Remembering this fault was caused by the AA technician shorting the HV Secondary to ground I am thinking that it could be the starter motor again, as these were the exact same symptoms I had 7 years ago when it was first delivered, I then assumed then that someone had tried to jump start it whilst in transit and damaged the starter as it would spin fine but not start.
Does anyone know the voltage required to fire the coils whilst cranking please ?

 

Thanks Steve, curious thing, went in to the garage this afternoon and tested at the digiplexes for the TDC sensor which runs both Digiplexes and got the required 680 Ohms, so tried to start her and she fired straight up. Ran it for a bit and switched off and then switched it on again, and again and again, so it seems that today all is ok.
I will test all cabling from sensors to coils in case I have a damaged core causing an intermittent TDC sensor.
What I can't fathom is the condition from starting fine to not by the shorting of a coil. ?

Thanks again for every bodies input.

 

Update as to where I am at.
Thanks again for everybody's input this is really a valuable knowledge base.
I was going through all of what I had done and the one thing that struck me, was the ignition in fact working (ie did I really have a spark) and was I diagnosing it incorrectly.
The way I was checking for a spark was with a timing light which had always proved reliable in the past, so this morning I tried to start the car and it nearly caught straight away, but after that nothing. I unplugged the cold start valve and she fired up (albeit rather rough), so I tried the timing light on it whilst running and no flashing timing light.
I then tried the timing light on my 928S and it was flashing fine. I can only imagine that the batteries I am running the timing light from when using it on the 308 weren't charged enough to flash, even though the display came on on the timing light ( I was running it off two 6v lead acid batteries from a children's ride on car).
So I am happy that the car now starts, next is to test the cold start injector and also see if its firing on all 8 cylinders.
Thanks again
Glen