CATERPILLAR 428 D. Injector pump leak repairs

There is diesel leaking out the bottom of the injector pump from the drain hole, so I pull it to pieces, put new seals in the pump and put it back together and run it, being careful to keep the timing.  CAT 428 D. 2003 has a Perkins 3.9 l or 236 ci 4 cylinder turbo engine with a Delphi pump