Not getting fire to the coils

A friend brought me a 2004 chevy
suburban 5.3 l. It was turning over but
wouldnt start said they was changing
fuuses around and then it would start
and the wires down at the starter they
moved them around to get it to
start.have no idea which fuses but did
tighten wires at starter and replaced all
fuses. Batt appears new but without
the key in it and doors all shut ,
wuthout the hood light ,when i connect
the batt it spark pretty heavy as if the
headlights were on about that much
spark and appears that the batt is
being drained when i finally get charge
enough to turn over i get no fire to the
coil would it be the brain? Its dtiving
me insane. Lol.