Keep trying, and failing, to start engine - what am I doing wrong?

[Musketman12]

I have no idea what i'm doing wrong with burns either, I get my burn going 66 oxy 33 plasma, get the cold loop going with plasma, do hot loop, ignite, open vent, pop hole in the burn chamber and rcd the space under the tanks. This is exactly what everyone usually says to do, but every time I do it, it get's up to 1 MW and then drops to none and frankly I have no idea what i'm doing wrong.