Please find another mechanic. That one knows nothing of what he told you. Oregon fuel Injection can sell you a new check valve for cheap. All you do is unscrew the supposedly bad on and install the new good one. If that was your problem then its fixed. As for ALL the fuel draining back to the fuel tanks thru the return lines.. I call bs to that also....
Want to find where the air is leaking into the fuel system.. Do this before anything else. Remove the fuel filter bleeder return line and replace it with a clear piece of line. You can get the clear line at home depot in the size you need. Its either 3/16 or 1/4 inch. Then run the engine and watch for air in the clear line. Air seen in the line proves the air is getting in the suction line somewhere. Probably that short rubber hose from the frame to the mechanical lift pump. That line sees plenty of use from the engine moving all the time its running. So buy a piece of 3/8 rubber hose about 18 inches long. Cut to fit and your done. Watch the clear line for air... See none.. Problem fixed on the cheap.. But please see another mechanic but next time make is a real one. That other ******* has no idea what hes telling you to spend money on. Those of us here spent money on the cheapest items first. We have a collective base of knowledge far suppiour to any shop out there hands down. Theres not much this group doesn't know.
Again I'd suggest Mel AKA Agnem or Russ AKA Typ4 both offer good fuel system parts for these units!
