CLK200K starting issue.

[Animal]

Hello all from a newbie, I have a 2009 model cabrio 46k (owned for 18mths) which I'm v impressed with so far but it's developing a starting issue, which only happens occasionally, engine hot or cold. Engine takes a long time to fire but runs fine once started. Battery seems fine as turning over quickly. Plugs renewed at 36k, car is serviced annually by an indie.
Anyone heard of this issue before? Any ideas much appreciated.

 

[brucemillar]

Could be the Crank Position Sensor starting to fail. They usually fail when the engine is hot. Car turns over but will not fire or takes longer to fire.

I would get it plugged into a STAR machine as it should have stored errors if it is the CPS.

 

[Animal]

OK thanks, will look into that, are they easy to change yourself? I'm ok with a bit of mechanics, changing brake discs and pads myself etc