D-17 Hard starting

My D-17 series 3 will not start if it sits out in the rain. It seems to get wet very easy. Is there something I can spray of the distributor cap? Or is the problem elsewhere? If it won't start and it has stopped raining I can remove the distributor cap and let it sit open for about 1/2 hour and then put it back on and get it started. My daughters wedding is coming up and I am pulling the wedding party around town on a hay ride and don't want to be delay if it won't start.

Its possible you have a cracked distributor cap.  A new one could solve the problem.  However, in the past I have used WD40 inside a distributor cap to get an old Ford pick up going after a heavy rain.

I would replace the cap, also I don`t know the condition of your wires. The cover on the plug wires will break down over time and bleed voltage because moisture will get through. I would replace the wires unless you know for sure they are in good condition. I leave my D17 outside in the rain at times and don`t have a starting problem. When you pull the cap up when it won`t start do you actualy see moisture inside, if so the cap may be all you need.