Walbro Fuel Pump for 2008 -11 STi/WRX/LGT Install:
5.) Remove the giant O-ring from around the assembly and place it somewhere safe. Next you will need to use patience and the flathead to pop all 4 tabs holding the top of the assembly off. Once you have done this, set the top piece somewhere safe.
6.) Once the tabs are loosened pry the cover off to expose the innards. You may need to disconnect the connector from the fuel pump as well. Make special note of where the various O-rings are located for re-installation. There is a small C-clip that needs to be removed before the whole assembly can slide off.
7.) On the bottom portion of the fuel pump is a compression washer that holds the fuel filter to the pump. Use a small flathead to pry this off and remove the filter. Place both aside for further use later.
8.) Grab two small flatheads and shove them in the openings like shown below. This will allow you to remove the fuel pump. It requires good force so use a pair of pliers if needed.
9.) Plug the holes with some paper towels so you don’t get plastic shavings in them during the next steps.
10.) In the picture below you will see where the housing needs to be shaved down to accommodate the Walbro’s size. You must shave all 5 of the spots down as far as possible so the walbro can slide in far enough to allow the whole assembly to fit up snug. I recommend using a pair of dykes first to snip off the big pieces, then use a dremel to smooth it all out.
When completed it should look similar to this: