kangoo very strange starting problems

hi this is my first post, I have searched other post but none seem to match this issue. sorry if its lengthy but want to make sure all the info is there.



the van is a diesel 2004 reg, always started very well. then one day no action. banged a set of jump leads on started first time. rest of the day no issues. same again next morning jump leads and no issues all day. I replaced the battery. next morning same issue. jump leads on started no issues all day. I have tried a jump pack but this does not work.



new glow plugs fitted, started second turn of the key for 3 days then back to the jump leads every morning but no issues starting all day.



new fuel filter fitted, no difference at all.



after a few weeks of this its been struggling to start even with the jump leads on in a morning some times I had to pump the fuel primer ball a few times to make it start.



now even with the jump leads on, primer ball squeezed and the glow plugs heated its still not starting., this is so frustrating if any body has had this issue or has any idea what it could be it would be grate help. thanks