mercedes 200t

my 1987 mercedes 200t wont start first of all it just died on me then after about 5 mins of trying it started it did this for about 4 times now it tries to
start but wont quite make it there is a spark and fuel but it wont go it seems to spit back through the carb when the timing chain seems a bit slack but the timing marks are aligned correctly could a slack chain be the cause?please help

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