How To Check For Leaking Fuel Injector
It’s possible that one of the fuel injectors is leaking. Normally, pressure is maintained in the fuel system after engine shutdown. Because of this pressure, a leaking injector would discharge fuel to its cylinder until the pressure was near zero. Burning off that excess fuel would lead to the black smoke on startup. Also, because the pressure in the fuel system is down to zero or near zero, a number of cranks on startup would be required to rebuild the pressure sufficiently for the engine to start.