Vw golf gti mk1 1979 wont start

hi everybody have gti that won t   start  mk1 series 1

have checked the following

fuel going to  distrubtor  is ok

fuel going  to injectors

checked injectors  while out of manifold and are all working fine

has a good spark

have opened vaccum plate on distributor while turning engine over  

have turned dizzy while truning over engine over left and right

could the cold start 5 th  injector  stop car from starting

not much  back pressure from exhaust



any idea what could  be problem  





     

compression test next!