Hello! I am new to this so any advice or tips will be much apreciated. I just got a 94 Z28 auto. I believe its all stock with 115000 mi on her. It wasnt running when i got it so here is a list of things that i have done so far. New opti-spark, waterpump, belt, thermostat, knock sensor, starter, plugs, wires, air filter, and fuel filter. Now here is my problem, I't cranks a long time before it will start and you can hear a slight (what sounds like spark knock) on take off if i get into the throttle alot. It was doing it really bad before i changed plugs and wires. Now it's not near as bad. When starting it sometimes it will crank for about 30 seconds before it will fire up. Holding the throttle open does not make a difference. Any help would be great.

 

Next investment s/b a fuel pressure tester. Try turning key on-off-on a few times to pressurize the fuel rails net time you try to start it and see if that fixes the hard start. Knock at take off could be low fuel pressure or other problems. You spent a boatload on money so far, if you have a laptop you can get a cable for $70.00 and free software to really analyze whats happening.