Hey Jon - welcome to the forum. Do you know what model EFM you have? A 350 and 520 (S15 or S20 stoker) are the most common; 700,900, and 1300 models are the big boys.
Take a look through the EFM section on this forum and familiarize yourself with the different parts and how they go together. Pictorial of all DF520 Stoker Parts and Assemblies
The most common wear parts on the S15/S20 stokers are the "gooseneck bushing", the burner plates, and the auger (worm) itself. If you clean all the coal out of the stoker and grab the auger in the bottom of the pot, there should be very little play in the bushing. The auger flights should not be sharp to the touch, if they are...replace the auger and bushings. The burner plates should be checked for cracks and excessive warping. Make sure the fines cleanout on the bottom of the pot isn't warped, and that it opens/closes properly. Other than that, a thorough cleaning of the ratchet mechanism and gearbox is probably in order - and be sure to clean the fan & blower housing. Inspect & oil the fan motor, or replace if needed.
The tankless coil area on the boiler should be carefully checked as well. Sometimes the gasket leaks and the boiler gets corroded...sometimes it is so bad that a repair plate needs to be welded on. If the gasket needs to be replaced, be patient with the nuts on the studs. A torch, some penetrating fluid, and a lot of patience is required for that job. If you rush it is easy to break off one or more studs.
Where are you located? You may have an EFM expert around the corner and not even know it.
One more - You can also find the DF520 owner's manual on the EFM website: http://c326988.r88.cf1.rackcdn.com/DF52 ... lation.pdf