You mentioned the valve adjustment already, condition of the injectors, fuel injection pump timing, valve timing and compression all can effect the fuel knock issue. If it is a fuel knock and it goes away after your engine warms up it is nothing serious.

Tests
pop testing the injectors

You are supposed to use the 2mm method to check the valve timing but you can get an approximation by lining up the timing mark on the back of the Camshaft Gear with the one on the front Bearing Tower and looking down at the Crank Damper and see what degree the pointer points to. There was some pics of this in the repairlinks.

A compression test to test the compression.

Checking or re-timing the Fuel Injection Pump.

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84 300D, 82 Volvo 244Gl Diesel