I have an 03 ram Diesel. I just replaced the LP because I thought that was the prob but obviously not. With both the return and supply line disconected I can easily blow in either line, but when I blow in the return it will actually just pressurize the tank till I stop blowing then the air will blow back in my face (this happens when the fuel cap is left on), I assumed blowing in the return line would push fuel out the supply line. I can blow into the supply line and air comes out the return line.... However...when I suck from the supply I can't get nothing, I just can't get fuel out of my tank.