SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I have a self installed sprinkler system that runs off my garden hose and hose bib. It has been installed for 2 years and has run beautifully. I have blownthe system down each of the past 2 years using an air compressor and have made sure everything is out. This year I started it up and have very low pressure. The system only has 4 heads in use. 1 - 3/4" Hunter singlestream , 2 - 1/2" Toro multistream, and 1 - 1/2" Orbit single stream head. There are several (3) spots that have been capped off that I previously used for bubblers but no longer use. The longest run to any head is about 55'.
I have the system set up on a battery operated timer, and it has worked great in the past...now I am lost.
Do they make anything as a pump, that can increase the water pressure? Where would I get it? How would I install it?