After getting my 190E 2.3 Repainted, I got to the shop and went to start it to drive it home, but it wouldn't start. Kinda felt like there was no gas, I'd get it to fire, but it would never actually kick. Well, after about 5 or six times of trying, I got it to where it would JUST BARELY be running with my foot all the way on the gas, after about 10 seconds, it fired clean, some black smoke puffed out, and it was fine. Turned out the fuel injectors were clogged, dunno how they got clogged, but they were. Sounds similar to what your describing, so keep trying!!!! Once you get it started, run it hard on the highway a bit.