After the car has been sitting for a few days, and you know it will be hard to start, try bleeding the fuel system. Crack the bleeders on the fuel filter and on the injection pump and prime the system before you start it up. Mine had the same problem, and it eliminated other problems from the equation. The original engine in my '67 was rubbish. It was severely worn out at a fairly low mileage. Everything inside it was pooched. It may have been due to a lack of maintence, but I've also heard of bunk engines of this vintage.

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1967 200D FINTAIL (in service)- 86K
1983 VOLVO 244 DL (daily driver)- 300K
1988 VOLVO 244 DL (ice racer) - 345K