My Civic Won't Start

I just changed the Exhaust Manifold and both O2 sensors on my 2002 Honda Civic LX. When I initially turned the engine on there was white smoke coming from where the upstream sensor was connected to the Manifold. I eventually found out that I was sold the incorrect upstream sensor. I'm not sure if I saw white smoke because the sensor wasn't correct or if it was just because I didn't have it screwed in tight enough. I purchased the correct sensor and when i went to start my car, it turned over but didn't start. It's not the starter, it's not the battery, I changed the plugs so it's not them. I wonder if it's the fuel pump, fuel filter, or coils. Does anyone have any suggestions?

White smoke usually means water in the exhaust, look for leaks in the engine.