Gatchachubie

My Merc do not start when it is cold.I check the pump and the accumulator and it is al in order. The cold start and the cold start time switch been replaced. The WUR is also check and work correctly. Fuel distributor fuel pressure seems to be right but I cannot test the pressure to the injectors. When the car do start black smoke emerge from the exhaust and idle rough.
Is the injectors blocked and how can I clean them if posible.
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