Ok...... There is more
I have fitted a "Y piece between the fuel filter and the fuel rail. 1 arm is to a pressure gauge and the other 2 arms have taps on them so I can shut them off individually to check for pressure leaks from both sides of the fuel line.
After running running the engine I have shut off the fuel from the filter and then in turn, fuel to the fuel rail. Both sides held pressure for quite some time but eventually lost pressure. But it took over 1 hour to do this. So I assume the injectors and the non return valve on the fuel pump are working reasonably well.
The next day.
Tried to start the car and no start until I realized that I had not opened the tap to allow fuel to flow. So opened the tap but car would still not start.
Ah..... There was that noise from the IAC .
After disconnecting and reconnecting the battery the mystery noise and no start problem gone .
Car starts and runs OK.
So the noise, and the "no" start condition both occur after trying to start the car without fuel pressure in the fuel line .
But why
Fuel pressure regulator problem ??
This is connected directly to the fuel rail and there is only a vacuum hose connected via a solenoid valve between the inlet manifold and the Fuel pressure regulator.