My beloved and hard working PT422 started giving me fits this week as I tried to use it in sub-zero weather. Over the fall I had experienced some surging and an intermittent stall after running up a hill or under a hard load for a while. This week it wouldn't stay running off idle or would start after sitting and then die in about 10-30 seconds. New fuel lines, plugs, and fuel filter, no change. Tore the carb down, cleaned and reassembled, no change. In a moment of weakness I was about to order a new engine but then I decided to pull the top off the carb. When I did this I could see that the float bowl would slowly fill up but not refill fast enough and the engine would starve out and die. Only one thing left- the fuel pump. I connected the carb fuel line directly to the new filter at the tank, and then filled the tank half full, with the level way above the top of the carb float bowl. It fired up and ran strong. Ten minutes later I had the snow cleared off my driveway, and brand new pump on order from Ebay.
As I think about it, though, do I really need to install the new fuel pump? If the tank level is above the carburetor level and the float valve is doing its job keeping fuel at the right level, and the engine is running great, is the fuel pump really necessary? I am guessing that the Robin engine is a general purpose motor and the manufacturer has no idea what kind of installations it will be used for so they add a fuel pump. On the PT the tank is in a good location for gravity feed.
As I think about it, though, do I really need to install the new fuel pump? If the tank level is above the carburetor level and the float valve is doing its job keeping fuel at the right level, and the engine is running great, is the fuel pump really necessary? I am guessing that the Robin engine is a general purpose motor and the manufacturer has no idea what kind of installations it will be used for so they add a fuel pump. On the PT the tank is in a good location for gravity feed.
