The 3DNX25GSI was a popular pump from CAT Pumps and was used in many pressure washers. It is no longer manufactured, but you can still repair it as CAT Pumps still makes replacement parts for it. This pump physically resembles a number of other pumps with similar names (such as those in the 2DX or 3SP series of pumps), so make sure before starting any repair or replacements jobs that you are looking at the information for your pump.
This pump has a max PSI of 2850 and a flow rate of 2.5 GPM.
Click here for a Parts Breakdown Diagram
Click here for a step by step valve repair guide
Click here for a step by step seals repair guide