first thanks for feedback info very interesting and helpfull, no pressure sensors in system so kts cannot read, went back to basics, physical check of valve timing- all ok, then recheck compressions (they had been checked before and were ok) noticed this time on second cylinder test, engine sounding like it wanted to start, also signs of atomised diesel comming from other glowplug "holes", suspected engine drawing in air through glow plug holes so started looking for restriction on inlet system throttle flap stuck shut - it was solid, removed all carbon and released flap and engine started .Reconnected scope now "seeing" injector switching, the crank sensor still only showing 1 volt right through rev range? but this does not seem to restict starting or performance