didn't mention if engine has turbo, but if so, failed turbo can cause the black smoke and stalling problem.
acts like a choke on the intake side if turbo wont spin
most defects have been coverd before in other replies ie... heavy black smoke is either lack of intake air or heavy fueling. can be a blown tip on injector, causes fuel to be injected in a stream instead of atomized. one injector bad on a multicylinder engine wont usually make it stall, just misfire, inother words a four banger will probably run with a bad injector but a twin or triple might not.
overfueling in and of itself would just cause engine to run at high speeds, not the black smoke unless heavily loaded or lugged down,so it probably isn't the injector pump doing its majik on all cylinders but a case of one cylinder having a problem or no insufficient air.
could even be something off the wall like the engine jumped time, fuel at wrong time
white smoke is incomplete combustion, usually low compression. mentioned hard starting and only running on one cylinder until engine ran for 30 seconds or so. incomplete combustion burns your eyes outta your head, just a lovely thing.