typically, cam/fuel pump/crank indexing issue after this kind of maint. if the cam/pump/crank are not indexed correctly the valves and in-turn the fuel timing will be off.
here's a free factory service manual for your 2lt diesel engine for dl.
http://www.ncttora.com/fsm/1985/l_2l...air_manual.pdf
pg 35 (EM-26) for belt indexing.
not sure what vehicle you have, but if you need a free service manual you can check this page for dl,
http://www.ncttora.com/fsm/