[Ford-ferguson] Ford 640

[Don Brown]

My Ford 640 dies without any consistent pattern that I can figure 
out.  Sometimes I can run it for a couple of hours before it dies, other 
times I'll run it ten minutes and it dies.  I've always gotten it restarted 
but I've always tinkered with something before I tried to restart it so  I 
may have masked any clues that would be helpful.  A mechanic friend 
suggested that the screen on top of the fuel cut off valve might be 
occluded, restricting the last few gallons of gas,  so I filled the gas 
tank but the problem persisted.  I pulled the plugs and they had a thick 
coat of carbon, which I scrapped off.  I pulled the coil wire and noticed a 
whitish coat of oxidation on the inside of the connection.  I know it 
shouldn't be there but I don't know the cause.  The sediment bowl was clean 
and gas runs freely from the tank to the bowl.   The motor does not burn 
oil, it idles good and has normal power.  I will replace the plugs, plug 
wires,  coil/distributor wire, points and condenser..  The dust cover in 
the distributor is torn and I'll replace it but can that cause a 
problem?  I assume that a distributor problem would be indicated by 
performance, am I correct?  The 12 volt system was installed about four 
years ago and the tractor ran fine until the last few weeks.  The most 
recent repairs were a new head gasket and a rebuilt radiator.
Any ideas?
Don