1964 John Deere 4020 22T Serial# 89,000 fuel system bleeding.
This was a very expensive learning curve... I bought the tractor as is and it had been parked in a shed for two years. I know the previous owner and knew that it had been driven to the spot and turned off.
I knew that the fuel was very old and just wanted to run it long enough to get it home (two doors down in town) and drain the old fuel and change the filters. To make a long story short, there was no smoke when turning it over. In the time that it sat, the metering plungers(?) in the pump distributor head had seized and the thirty psi vane pump pressure at cranking was not enough to break them free. One injection pump overhaul and six 25 mm injector rebuilds later ($$$$) it is running fine and I will do my best to use it enough to keep the fuel fresh from now on.