Won't start. Clean injectors or something else?

[Jemo]

I just got my 5.3L finally wired up and ready for the first start today. The fuel pump comes on as it should, it turns over, and has spark but no start. We turned it over so many times that the battery finally died. It seems like it was getting better. Early on it would turn but not try to start. At the end it felt like it was starting to kinda catch on but never did.

The manifold I used has been sitting for a long time so the only thing we can figure is the injectors are just a little clogged. Should I just charge the battery and keep trying until it runs or do something else?

Thanks,
Jeff