I can't seem to get my Imp to run off the Main fuel tank, does it take a lot of cranking to get the fuel up from the tank with the mechanical fuel pump? My fuel tank selector valve appears to use the 6 o'clock position for the Aux tank, 9 o'clock for the main tank, and 3 o'clock to shut off the fuel flow, does this seem about right? Is there some trick or something I am missing?