Model G21 (01536-1) 2100 PSI
This thing did not work right straight from the store. At any rate, here's the issue: Once the pressure builds up it's fine until I release the trigger. Then it goes to standby mode (low pressure). But when I squeeze the trigger again, very little pressure is present - it just puts out slightly more water than standby. With the trigger wide-open, I have to change the nozzle setting - either push in or pull out to gain the high pressure again. A guy at my lawn maint shop said it's likely a valve that is not sensing the pressure change and opening or closing. He suggested a pump rebuild kit. I found a site, but they have several kits for the different parts of the pump. Trial and error could get me a rebuilt pump but damn close to the price of a new pump. I think I need this (unloader) kit: