Tractor Repair: JD 2940 deisel, crankcase oil, fuel pump filter

Question
Tractor has had two (to my knowledge) instances of fuel contimation of crankcase oil. Engine will
start and run if towed. Will not start with starter even using starting fluid. Even with strong batteries, cranking seems deminished like a hydrallic lock. If it starts, runs for 2 seconds and dies. Could the dilution of oil cause the hydrallic lifters to not allow the valves to open? Or could the valves not be opening due to camshaft worn out? Tractor is 1981 year model and started wonderful until last oil dilution. Fuel system is fine, fuel pump, filter and injector pump and injectors. Fuel is mixing with oil due to leak from injector pump (best guess after talking to JD dealer and other farmers). Thanks Bishopville, SC, home of the SC Cotton Museum.  

Answer
George I feel that it could be correct on all counts but you will not know unless you strip it down and look I need a holiday as I am in Australia I can come look at it if you supply the ticket.
No sorry George look at removing the head and see what clearance is in the bores oil dilution is a bad thing it causes all sorts of damage so i feel a strip down is the best for your tractor.
Keep me informed to what you find please George


                    Regards Danny Last