Outer Limits 4x4 Board

I have a 92 model GQ 4.2 diesel without a turbo. Overtime it has slowly being getting worse and worse with the amount of smoke coming out of the exhaust. It is a blackish/greyish coloured smoke and was thinking perhaps injectors or diesel pump could need an overhaul. The car is just short of 260,000km's and gets a full service every 5000 kays. Any info on what to check and look for would be appreciated.

First - Air filters.

Check also injector Nozzles--hopefully at that km they should have at least been done, also check tappet clearances. Injection pump MAY need checking if above dosent reduce smoke.

NIck

injectors might need servicing?
i found that when my sd33 started getting real smokey, it turned out the battery was on it's way out, not glowing the plugs properly which meant less fuel burnt and more out the back in black smoke...