check injectors fault

I have just rebuilt the megane 1.5 dci engine, took a bit to get timing right as had problem with camshaft, I have renewed all the valves and head gasket, when I go to start it iam getting a fault on screen saying check injectors, I havnt checked any thing yet and the only thing I havnt done is fitted the alternator belt, not sure if that would have anything to do with it, I havnt checked anything yet as I don't know where to start

thanks