07 1.9TDi Starting problems..

Hi All, bought my Ex Taxi cab, high mileage but well maintained, lots of new bits, new cams and top end re-build, Injectors, flywheel, rad, oil pump, fuel pump. sump. glow plugs, but it often doesn't want to start properly when its cold,. takes a bit of cranking, runs fine once started, seems like its not keeping fuel in the injector rail. .. its had several code reads, new battery, new starter motor, I call it Triggers Brush.... 

it seems ok when parked downhill and when warm. 

running out of things to replace... HELP!!