Tony,
What are the specs on the DC pump? You do have 8 100 watt panels, but the way you are using them, you have less than 500 watts available. I believe you are using "12 Volt" panels. They are not ideal for a 48 volt system. Read up on solar panels using 60 or 72 cells per panel. Also, do you know the chemistry of the panels?
I know this all sounds technical, but after you answer these questions, it will be easier to help you set it up correctly.
