I have a D6D, and it is dead in the water-diagnosed as injection pump problem by the tech-fuel dribble out when when line disconnected from bonnet and cranked.  Finding a replacement is a problem for them-and little info available because the engine serial and machine serial arent accepted by any online site-not even Caterpillar. I assume its because of the age of the machine so I came here. Dozer Serial is 4X4146, Arrange Number 8P1544. the engine is a 3306 (cant tell if its a 3306B-same problem with no clear way to tell as the serial doesnt show up anywhere)-engine serial number is 3N80264, Arrange Number 7N1539.

I would like any help anyone can offer-the machine is a workhorse here on my ranch-and I need to get it going again. I have a full service manual and parts book I got on ebay, and I dont think replacing the entire governor and injection pump assembly would be needed-maybe. The assembly looks like it is part number 4N1836-but cant be sure as there are multiple figures depending on Engine serial apparently. Picture attached for help. Will be trying to remove filter today to see if there is a part number behind it.  Thanks for any help in advance-I need it!

Change the fuel filter and clean out the separator screen, blow out the fuel line from the tank and see what happens.
Bob

Well-pulled filter-and now have the part number from the pump-but after seeing what came from the filter-betting you are right about the fuel system before the pump before looking too hard at the pump. Look at what came out of the filter-the old old old filter. Where is the separator screen? Thanks for the help so far!

You really need a OMI for your D6D. The Operation and Maintenance Instructions contain much valuable info that will save you time and money
Good Luck,
Craig

The separator should be on the right side of the engine, a square glass bowl might as well change it. Be sure and drain the tank drain and blow back thru the fuel line from the tank.
I think that number is the pump body casting number.
Good luck
Bob