i pulled apart my injectors the other day. mk3 TDI AHU. the manual has about no information on the insides,pulling apart TDI injectors. i went to clean the 'lower' part, did ok, the first two, i tentatively went into the 'upper' end, cannt be sure of the results. and i cannt find an official or accurate pic of injectors innards. so as-i-recall, i had the injector body, as the top area had no significant contamination. putting back together like i said, had the body, put small spring in, has a retainer, then the pin goes in smartly in the retainer, then it looks like the small 'spacer', then it looks the big 'spacer' then big spring, has a retainer, pin goes thru, to the pinned 'cap', with a bushing, then nozzle, and gets screwed on. (nozzle has that plunger/pin in it)-that is after cleaning lower.
can the use a diagram of injectors.
another thing one of the 'upper'(had taken apart) i wasnt sure how pin set, as i put it back. everything seemed to sit evenly, but pin was even with 'pinned cap' bushing insert. the other one the bushing (in 'pinned cap') sat high, as though the big spring retainer wouldnt let it sit flush with cap, the pin set higher, and looked better.