Sunbird starting problems

Have read lots of messages that say the sunbird line has an intermittent start fault, almost like it has a mind of its own or is like a woman, will go when it is ready. I have the same thing with my '91. Lots of juice, cranks well, but some days, particulary damp ones, and no joy. Leave it for 15-20 minutes, and away we go. Seems to be worse if I park on a uphill slope. Have to face down hill. Have changed the plugs, distributor and rotor, and the inline fuel filter. Also have used di eletric grease on the plugs and points. Trying to think of any thing else that might affect the car. IF anyone else has the same or similar, and has solved the equation, let me know. Thx