If car won't start, I guess getting hot and burning off oil can't happen so you shouldn't be having smoke. Did the old spark plugs look bad? If the new ones are in and you're getting smoke, would pulling them to look possibly show brown, white or black, even though your car won't seem to start? To test injectors, you use a voltmeter, set it to check resistence in Ohms, then check each injector at the plug (unplug wire harness, test injector prongs that are now exposed).
how-to-test-fuel-injector-resistance-t416697.html Engines need spark, air and fuel. What else have you checked?