Cold starting was a major issue with 30 and 40 series Deere tractors. Many were poor starters at 50 degrees F when new. Others would start at 20 degrees F. We had many upset customers - especially when trading in a 1960s 4020 that always started well at 20 degrees F, and then taking home a new 2940 that would barely start at 60 degrees F. There's a lot to it - and I don't want to write a book on the subject (and I almost could). You didn't mention if this is a new problem, or the tractor has never started well since you've owned it. First - it must crank fast. Most starting problems with Deere diesels are caused by the hydraulic system putting too much a load on the starter motor. If in question - install a $10 manual pump-detroker. Often, it makes a night-and-day difference in cold starting. As to actual engine problems? A poor valve job with valve-heads ground too deep into the head, static injection timing too retarded, piston height above block too low, valve lash excessive, cranking fuel delivery too low in the injection pump, etc. all can cause poor cold starting. Also, a more major defect that is common - it the top piston rings shattered to pieces. Often a Deere that does not cold-start well, gets made much worse with ether starting. Especially if the intake-manifold ether orifice is bypassed and ether is simply sprayed into the air-intake. Once the top rings break , you've got an engine that can barely start at 70 degrees unless ether is used - but once warmed up runs pretty good.
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