Repairs to my Komatsu PC220 LC Fuel System - air in filter 

I struggled for several days working with my Komatsu pc220lc excavator and are leaking into the fuel system. I replace the fuel line from the tank to the primer pump, and the fuel filter to no avail. My local Komatsu dealer recommended I replace the primer pump since they go bad over time. I replaced it in about 45 minutes, it solved the problem!