A pump is a device for pushing air, water or other fluids through tubes or pipes. To pump is to perform this pushing. Therefore, to pump money somewhere is to put money into that place for some kind of purpose.
This is easy to demonstrate with an example from politics.
Example: Last week the U.S. Chamber of Commerce pumped more than $10 million (U.S. dollars) into states important for the upcoming mid-term elections.
This is simply giving the reader the (correct) impression that this is a significant amount of money relative to normal levels of political advertising.