My brother just told me his '87ish JD 850 is on its way to the dealers as it started to "knock" loudly. He said the dealer seemed to think it was an "injector". This tractor has a Yanmar engine, etc. It only has about 1000 hours on it and has literally been garage kept, with all servicing by the dealer. Anyone out there have any ideas?? Sounds like an injector pump to me, but I haven't heard the engine since the knock started. Any help would be appreciated including the potential costs if its a pump (not sure what type of pump is on this --but do know that Bosch pumps are a bunch if bought new. Thanks in advance for any help!! BobG in VA