[Vwdiesel] backfire???

[cass]

hi kids..
so..
do diesels backfire?
mine may have .
at first i herd a pop after starting and driving may 1/4 mile.
 (1.6 na)((1980)
a check of the motor showed a injector return line popped off/loose..
though line could have been like that for a bit.....or that coulda
been the noise
(im going up  to make sure return line isn't plugged)
on the way home..
it made a noise like a backfire again..more a rattle..like i had
driven over a piece of tin on the road(looked..no tin on road)
all the return lines are on still...
haven't done anything different to the motor in a while..same diesel
ect.
the only thing i can think of was i *may* have put too much two stroke
oil in fuel...
would that cause it to backfire like this?
other things to check?
:o(
thanks in advance..
cassie