If it uses oil, likely it has serious cylinder wear -- that model was known for soft cylinder liners in the original design and hence pre-mature wear (they normally run several hundred thousand miles before giving trouble.).

You should do a compression test and leakdown test to determine what is going on -- worn out valve guides will do the same thing (oil goes past the valve stem and gets burned, and the valves are worn out and don't seal).

Check valve clearance -- these have manually adjusted valves, and if ignored, they close up and the intakes will stay partially open cold, makes them hard to start and rough. Leave them a bit wide and re-check, as carbon on the valve stems can also hold them open, once adjusted, the carbon wears off and they will go tight again.

Replace the hoses between the supply line and the lift (hand) pump -- it's likely rotten and allowing air in. If the hand pump leaks fuel when you operate it, replace it, it's also leaking air in.

If you get copious clouds of unburned diesel while attempting to start, the fuel system is OK -- if not, you have a leak. Once fixed, it will take a bit to get all the air out of the pump, so run it a while.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!