Volvo: 850 GL cannot start engine, air mask, starter relay

Question
my car 850 GL i dun no wht probulem i chenk my batter,alt,plags,plags cabel,air mask,fuel punp,fuel    injetion,starter relay also cant start.
so sad i dun wht i can do now.

Answer
Jock,
You do not say what happens when you turn the key? Did the engine turn over and fail to start? If so is the engine getting fuel and spark? Is the fuel pressure to low, bad pump, or not operating at all, pump or relay. Or the engine makes no attempt to turn over(crank)? Battery to weak, cables dirty or loose, vehicle not in park, gear postion sensor not adjusted. Perhaps the engine was flooded and has washed away the cylinders and now has low compression. In that case a small amount of oil can be squirted into the cylinders to bring back that lost compression if they were washed down.