ok... lets start with simple things.. fuel can become "stale", so you might want to siphon it out... go to local parts store and buy/rent siphoning tool - a tube with rubber thingy that looks like an old fashion enema bottle. replace fuel with fresh - this will cross out one item on the long list of items to check... then, once you have fresh fuel, get a fuel pressure gauge, to see if fuel pump is working... the pump primes the fuel lines only when you attempt to start the engine, and if the motor dis not start, the pressure, if there is any, will cut off to prevent "flooding" - in reality, these engines don't "flood", but i am using it for simplicity... so, basically, do what upallnight said...