Motor cranks but won't fire after starter was replaced. 5.3 liter

5.3 liter replaced battery truck started for a few
days after I bought it. Stopped starting and banged
on the starter it turned over and drove it to my work
to pull the starter. Disconnected battery took
starter out took it to orielys got a new starter.
Installed it and now it will only crank no fire. Pulled
a plug and they are dry. Have not tested anything
else because I am not sure what to test and what I
need for tools to test anything. Was I sold the
wrong starter. I tried to get my money back and
core but they would t do it and instead tried to tell
me I had bad connections or possibly needed
shims? Not sure why they would sell me a starter
that would need shims but that doesn't seem to be
the case because it cranks really good. I also
pushed valve that looks like a valve stem and gas
is shooting out. Help please and thank you