wr quattro starting issue

[Anth445]

For some time now i have had an intermittent starting problem which usually occurs when the engine is cold and typically after I have reversed out of the garage and left it on the drive for a while. When I go to start it quite often there is a noise from the drivers side of the engine similar to a grinding worn bearing. The car won't fire up and when I turn the ignition off this noise continues to run for a few seconds then stops. Its like something is still turning after the engine stops. I then have to crank the engine for about 20 seconds with full throttle before it eventually fires. The noise I've described is never apparent the second time I crank the engine and it will start ok after that. The fuel pump, accumulator, fuel filters, metering head and injectors have all been replaced over recent years, injectors twice. This all seems to happen more often when the weather is warmer for some reason and the noise only once when engine cold. I have also heard the fuel accumulator making a 'boing' nose every few minutes when the car is switched off. Is this normal. Any ideas as this is really annoying.