Replacement Injectors

HI, I`m hoping i can get some help from 1 or 2 people. I have recently bought a 1990 2.5 TD 110 CSW. It was running a bit rough, irratic idle, blue smoke until it warms up and struggles up hills. I had a look at the injectors and they looked like they had never been changed and i believe it is recommended that they are changed about 60,000 miles. My landy has done 136,000 so i thought i would make the investment and buy new ones.
I put them in today and there was a loud knocking sound and loads of smoke, i did what it said in the hand book about releasing the small bolts on top of each injector but thismade no difference.It got to the stage were ihad to re-install the old ones again to get it running.
PLEASE CAN ANYONE HELP ME!!!!!!!!! I`M A NOVICE WITH LANDYS AND DIESELS.
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If those injectors have been sat on the shelf for a while they could be gummed up and need dismantling/cleaning.Also depending on where they came from they might need adjusting to suit as they often are supplied unset as there is more than one pressure setting for those injectors.

Thanks for info, but can you elaborateon how they can be cleaned and adjusted as it thought that they were just a sealed item.The injectors were bought brand new ,not reconditioned from Bearmach.

If they came from Bearmach they will need setting on a pop tester - often the top cap will be slack to indicate they have not been set to the correct opening pressure.Take them back to your supplier and ask them to set them for you.