I've bagged one of these engines for a snow blower project, its pump is a Lucsa CAV rotary. The tach showed 1300 hours but the engine was missing badly as one tried to leave idle. Compressions ran 420-425 psi. Several 'experts' all suspected injectors because it was assumed that only one or two jugs were affected while pump problems would affect all of them. Three injectors were shot and that's been fixed, but no joy. I pulled the head suspecting damage but the cylinders are all alike, clearly visible crosshatching (photo) and barely a ridge which is likely just carbon (all in all what a 1300 hour engine shoul be). If there is any damage it might be at cam or crank level (I now doubt that). Next wek I'm going to look into the pump, might not even open the bottom end depending on what I find there.

cyl-1-xhatch-crop.jpg

Question:
Could a pump problem of this magnitude arise at only 1300 hours? What sort of pump damage would result in very rough off-idle while idle itsef was not that bad?

Thanks a meg.