After the fuel filter was changed the engine has a long crank if left to sit for more than 15 minutes.

Fuel system pressure decays after the engine shuts down. The high pressure decays rapidly, from system pressure (around 280 bar @ idle) to 0 bar in 2 seconds. The low-pressure side decays rapidly from 3800 millibars for 3 seconds or so then slowly to 0 over the next 20 mins or so. thus resulting in a long crank to start.