Hello,
I have a TS3 in an old dumper too.
I can't help you with your question, aside to say that it sounds like it's over-fuelling (as others have also said...).
Please can I ask you a question about yours?
Mine starts first touch but when it does so, it often goes to immediately to a peak of very high revs before rapidly dropping to tick-over.
Does yours do anything similar?
Best wishes,
Andrew.