the new edition, 68 1/2 cab 289. Seems to be running out of fuel. Put a clear filter on, will run for a good 1-2 minutes before boggin down like it's running out of gas. Filter still a little more than half full. pump it starts back up and does it again. Could it be just crappy gas? It does have an old electric fuel pump to replace the vaccum mechanical pump. I do see the clear filter getting lower wnd lower after repeated tries. Maybe just a weak pump? doesn't seem to have any vacuum leaks. any ideas? (also, which way on the manual selector valve is for main tank? i'm thinking towards driver's side) Thanks guys and gals!