Car consumes lot of fuel and emits black smoke?

A lot of fuel getting consumed,in that case check the fuel related components, that is fuel pump,fuel filter and fuel pressure regulator.
For black smoke problem, inspect the fuel injectors, if they are getting clogged or got worn out causing this problem.Also inspect the spark plugs and coil packs.
Check Fuel pressure regulator on the fuel rail, check Injectors for leak down.