If your think your getting to much gas and flooding the engine, pull the plugs and see if there wet. I don't think that;s your problem. If you car ran for 5 seconds I say you weren't getting any gas to your carb and it was just running from what was in the bowl, but 15 seconds and then dying sounds like your fuel pump starts to work and then stops. Easy way to check that is pull your fuel line and have a helper holding a can over the end and crank the engine. If your get fuel for a short time and then it stops, you found the problem.