\documentclass{article}
\usepackage{pdftexcmds}
\begin{document}
\ExplSyntaxOn
% works
\lua_now:e{
oberdiek.pdftexcmds.filedump( "0", "8", "\lua_escape:e{\jobname.tex}" )
}
~
% doesn't
\lua_now:e{
ltx.util.filedump( "\lua_escape:e{\jobname.tex}", "0", "8" )
}
\ExplSyntaxOff
\end{document}