Is the Engine still knocking after the Fuel Injector Line is tight on the Injector. As, you would expect it to be noisy when the was not tight as no Fuel was being injected into that cylinder.
I do not think there is anything in the Fuel Injection Pump itself that could cause a loud knocking.
I have seen instances were inside of the Fuel Injection pump the little Gear that makes contact with the Fuel Rack (that is a collor) has split or the screw that clamps it in place has cracked. When this happens you lose control of the Fuel on that cylinder.
If your Fuel Injection Pump Has a Cover on the side. you can remove the cover and watch to see if all of the parts move together when the Fuel Rack moves.
You can also see if any Tappet/Plunger Return springs are broken.

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84 300D, 82 Volvo 244Gl Diesel