starting probs...

I have a 94 High Top van..in the past 2 weeks I have had a prob starting it. The last time...a new starter ..it works fine for a day or 2 then it just clicks....I have plenty of power to the starter..if I put the key on I can jump it at the starter...could ir be a bad ground to the block? If so can I run a new ground to one of the starter bolts?
What about the small body ground off the ground cable...could that cause it not to start?
I forgot..it is wet when this happens...

Check the fusible link at the solenoid! I blew mine and replaced it but I didn't have a good connection. After replacing some corroded wire and re-attaching the wires my problem was solved.